This patch is a small change in enforcement of the uapi for
SECCOMP_IOCTL_NOTIF_RECV ioctl. Specifically, the datastructure which
is passed (seccomp_notif) must be zeroed out. Previously any of its
members could be set to nonsense values, and we would ignore it.
This ensures all fields are set to their zero value.
Signed-off-by: Sargun Dhillon <sargun@sargun.me>
Reviewed-by: Christian Brauner <christian.brauner@ubuntu.com>
Reviewed-by: Aleksa Sarai <cyphar@cyphar.com>
Acked-by: Tycho Andersen <tycho@tycho.ws>
Link: https://lore.kernel.org/r/20191229062451.9467-2-sargun@sargun.me
Fixes: 6a21cc50f0 ("seccomp: add a return code to trap to userspace")
Cc: stable@vger.kernel.org
Signed-off-by: Kees Cook <keescook@chromium.org>
This allows the seccomp notifier to continue a syscall. A positive
discussion about this feature was triggered by a post to the
ksummit-discuss mailing list (cf. [3]) and took place during KSummit
(cf. [1]) and again at the containers/checkpoint-restore
micro-conference at Linux Plumbers.
Recently we landed seccomp support for SECCOMP_RET_USER_NOTIF (cf. [4])
which enables a process (watchee) to retrieve an fd for its seccomp
filter. This fd can then be handed to another (usually more privileged)
process (watcher). The watcher will then be able to receive seccomp
messages about the syscalls having been performed by the watchee.
This feature is heavily used in some userspace workloads. For example,
it is currently used to intercept mknod() syscalls in user namespaces
aka in containers.
The mknod() syscall can be easily filtered based on dev_t. This allows
us to only intercept a very specific subset of mknod() syscalls.
Furthermore, mknod() is not possible in user namespaces toto coelo and
so intercepting and denying syscalls that are not in the whitelist on
accident is not a big deal. The watchee won't notice a difference.
In contrast to mknod(), a lot of other syscall we intercept (e.g.
setxattr()) cannot be easily filtered like mknod() because they have
pointer arguments. Additionally, some of them might actually succeed in
user namespaces (e.g. setxattr() for all "user.*" xattrs). Since we
currently cannot tell seccomp to continue from a user notifier we are
stuck with performing all of the syscalls in lieu of the container. This
is a huge security liability since it is extremely difficult to
correctly assume all of the necessary privileges of the calling task
such that the syscall can be successfully emulated without escaping
other additional security restrictions (think missing CAP_MKNOD for
mknod(), or MS_NODEV on a filesystem etc.). This can be solved by
telling seccomp to resume the syscall.
One thing that came up in the discussion was the problem that another
thread could change the memory after userspace has decided to let the
syscall continue which is a well known TOCTOU with seccomp which is
present in other ways already.
The discussion showed that this feature is already very useful for any
syscall without pointer arguments. For any accidentally intercepted
non-pointer syscall it is safe to continue.
For syscalls with pointer arguments there is a race but for any cautious
userspace and the main usec cases the race doesn't matter. The notifier
is intended to be used in a scenario where a more privileged watcher
supervises the syscalls of lesser privileged watchee to allow it to get
around kernel-enforced limitations by performing the syscall for it
whenever deemed save by the watcher. Hence, if a user tricks the watcher
into allowing a syscall they will either get a deny based on
kernel-enforced restrictions later or they will have changed the
arguments in such a way that they manage to perform a syscall with
arguments that they would've been allowed to do anyway.
In general, it is good to point out again, that the notifier fd was not
intended to allow userspace to implement a security policy but rather to
work around kernel security mechanisms in cases where the watcher knows
that a given action is safe to perform.
/* References */
[1]: https://linuxplumbersconf.org/event/4/contributions/560
[2]: https://linuxplumbersconf.org/event/4/contributions/477
[3]: https://lore.kernel.org/r/20190719093538.dhyopljyr5ns33qx@brauner.io
[4]: commit 6a21cc50f0 ("seccomp: add a return code to trap to userspace")
Co-developed-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>
Reviewed-by: Tycho Andersen <tycho@tycho.ws>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Will Drewry <wad@chromium.org>
CC: Tyler Hicks <tyhicks@canonical.com>
Link: https://lore.kernel.org/r/20190920083007.11475-2-christian.brauner@ubuntu.com
Signed-off-by: Kees Cook <keescook@chromium.org>
force_sig_info always delivers to the current task and the signal
parameter always matches info.si_signo. So remove those parameters to
make it a simpler less error prone interface, and to make it clear
that none of the callers are doing anything clever.
This guarantees that force_sig_info will not grow any new buggy
callers that attempt to call force_sig on a non-current task, or that
pass an signal number that does not match info.si_signo.
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
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Merge tag 'audit-pr-20190507' of git://git.kernel.org/pub/scm/linux/kernel/git/pcmoore/audit
Pull audit updates from Paul Moore:
"We've got a reasonably broad set of audit patches for the v5.2 merge
window, the highlights are below:
- The biggest change, and the source of all the arch/* changes, is
the patchset from Dmitry to help enable some of the work he is
doing around PTRACE_GET_SYSCALL_INFO.
To be honest, including this in the audit tree is a bit of a
stretch, but it does help move audit a little further along towards
proper syscall auditing for all arches, and everyone else seemed to
agree that audit was a "good" spot for this to land (or maybe they
just didn't want to merge it? dunno.).
- We can now audit time/NTP adjustments.
- We continue the work to connect associated audit records into a
single event"
* tag 'audit-pr-20190507' of git://git.kernel.org/pub/scm/linux/kernel/git/pcmoore/audit: (21 commits)
audit: fix a memory leak bug
ntp: Audit NTP parameters adjustment
timekeeping: Audit clock adjustments
audit: purge unnecessary list_empty calls
audit: link integrity evm_write_xattrs record to syscall event
syscall_get_arch: add "struct task_struct *" argument
unicore32: define syscall_get_arch()
Move EM_UNICORE to uapi/linux/elf-em.h
nios2: define syscall_get_arch()
nds32: define syscall_get_arch()
Move EM_NDS32 to uapi/linux/elf-em.h
m68k: define syscall_get_arch()
hexagon: define syscall_get_arch()
Move EM_HEXAGON to uapi/linux/elf-em.h
h8300: define syscall_get_arch()
c6x: define syscall_get_arch()
arc: define syscall_get_arch()
Move EM_ARCOMPACT and EM_ARCV2 to uapi/linux/elf-em.h
audit: Make audit_log_cap and audit_copy_inode static
audit: connect LOGIN record to its syscall record
...
Pull security subsystem updates from James Morris:
"Just a few bugfixes and documentation updates"
* 'next-general' of git://git.kernel.org/pub/scm/linux/kernel/git/jmorris/linux-security:
seccomp: fix up grammar in comment
Revert "security: inode: fix a missing check for securityfs_create_file"
Yama: mark function as static
security: inode: fix a missing check for securityfs_create_file
keys: safe concurrent user->{session,uid}_keyring access
security: don't use RCU accessors for cred->session_keyring
Yama: mark local symbols as static
LSM: lsm_hooks.h: fix documentation format
LSM: fix documentation for the shm_* hooks
LSM: fix documentation for the sem_* hooks
LSM: fix documentation for the msg_queue_* hooks
LSM: fix documentation for the audit_* hooks
LSM: fix documentation for the path_chmod hook
LSM: fix documentation for the socket_getpeersec_dgram hook
LSM: fix documentation for the task_setscheduler hook
LSM: fix documentation for the socket_post_create hook
LSM: fix documentation for the syslog hook
LSM: fix documentation for sb_copy_data hook
- Add logic for making some seccomp flags exclusive (Tycho)
- Update selftests for exclusivity testing (Kees)
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Merge tag 'seccomp-v5.1-rc8' of git://git.kernel.org/pub/scm/linux/kernel/git/kees/linux
Pull seccomp fixes from Kees Cook:
"Syzbot found a use-after-free bug in seccomp due to flags that should
not be allowed to be used together.
Tycho fixed this, I updated the self-tests, and the syzkaller PoC has
been running for several days without triggering KASan (before this
fix, it would reproduce). These patches have also been in -next for
almost a week, just to be sure.
- Add logic for making some seccomp flags exclusive (Tycho)
- Update selftests for exclusivity testing (Kees)"
* tag 'seccomp-v5.1-rc8' of git://git.kernel.org/pub/scm/linux/kernel/git/kees/linux:
seccomp: Make NEW_LISTENER and TSYNC flags exclusive
selftests/seccomp: Prepare for exclusive seccomp flags
As the comment notes, the return codes for TSYNC and NEW_LISTENER
conflict, because they both return positive values, one in the case of
success and one in the case of error. So, let's disallow both of these
flags together.
While this is technically a userspace break, all the users I know
of are still waiting on me to land this feature in libseccomp, so I
think it'll be safe. Also, at present my use case doesn't require
TSYNC at all, so this isn't a big deal to disallow. If someone
wanted to support this, a path forward would be to add a new flag like
TSYNC_AND_LISTENER_YES_I_UNDERSTAND_THAT_TSYNC_WILL_JUST_RETURN_EAGAIN,
but the use cases are so different I don't see it really happening.
Finally, it's worth noting that this does actually fix a UAF issue: at the
end of seccomp_set_mode_filter(), we have:
if (flags & SECCOMP_FILTER_FLAG_NEW_LISTENER) {
if (ret < 0) {
listener_f->private_data = NULL;
fput(listener_f);
put_unused_fd(listener);
} else {
fd_install(listener, listener_f);
ret = listener;
}
}
out_free:
seccomp_filter_free(prepared);
But if ret > 0 because TSYNC raced, we'll install the listener fd and then
free the filter out from underneath it, causing a UAF when the task closes
it or dies. This patch also switches the condition to be simply if (ret),
so that if someone does add the flag mentioned above, they won't have to
remember to fix this too.
Reported-by: syzbot+b562969adb2e04af3442@syzkaller.appspotmail.com
Fixes: 6a21cc50f0 ("seccomp: add a return code to trap to userspace")
CC: stable@vger.kernel.org # v5.0+
Signed-off-by: Tycho Andersen <tycho@tycho.ws>
Signed-off-by: Kees Cook <keescook@chromium.org>
Acked-by: James Morris <jamorris@linux.microsoft.com>
This sentence is kind of a train wreck anyway, but at least dropping the
extra pronoun helps somewhat.
Signed-off-by: Tycho Andersen <tycho@tycho.ws>
Acked-by: Kees Cook <keescook@chromium.org>
Signed-off-by: James Morris <jamorris@linux.microsoft.com>
Pull security subsystem updates from James Morris:
- Extend LSM stacking to allow sharing of cred, file, ipc, inode, and
task blobs. This paves the way for more full-featured LSMs to be
merged, and is specifically aimed at LandLock and SARA LSMs. This
work is from Casey and Kees.
- There's a new LSM from Micah Morton: "SafeSetID gates the setid
family of syscalls to restrict UID/GID transitions from a given
UID/GID to only those approved by a system-wide whitelist." This
feature is currently shipping in ChromeOS.
* 'next-general' of git://git.kernel.org/pub/scm/linux/kernel/git/jmorris/linux-security: (62 commits)
keys: fix missing __user in KEYCTL_PKEY_QUERY
LSM: Update list of SECURITYFS users in Kconfig
LSM: Ignore "security=" when "lsm=" is specified
LSM: Update function documentation for cap_capable
security: mark expected switch fall-throughs and add a missing break
tomoyo: Bump version.
LSM: fix return value check in safesetid_init_securityfs()
LSM: SafeSetID: add selftest
LSM: SafeSetID: remove unused include
LSM: SafeSetID: 'depend' on CONFIG_SECURITY
LSM: Add 'name' field for SafeSetID in DEFINE_LSM
LSM: add SafeSetID module that gates setid calls
LSM: add SafeSetID module that gates setid calls
tomoyo: Allow multiple use_group lines.
tomoyo: Coding style fix.
tomoyo: Swicth from cred->security to task_struct->security.
security: keys: annotate implicit fall throughs
security: keys: annotate implicit fall throughs
security: keys: annotate implicit fall through
capabilities:: annotate implicit fall through
...
All BPF programs must be called with preemption disabled.
Fixes: 568f196756 ("bpf: check that BPF programs run with preemption disabled")
Reported-by: syzbot+8bf19ee2aa580de7a2a7@syzkaller.appspotmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
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Merge tag 'v5.0-rc3' into next-general
Sync to Linux 5.0-rc3 to pull in the VFS changes which impacted a lot
of the LSM code.
On the failure path, we do an fput() of the listener fd if the filter fails
to install (e.g. because of a TSYNC race that's lost, or if the thread is
killed, etc.). fput() doesn't actually release the fd, it just ads it to a
work queue. Then the thread proceeds to free the filter, even though the
listener struct file has a reference to it.
To fix this, on the failure path let's set the private data to null, so we
know in ->release() to ignore the filter.
Reported-by: syzbot+981c26489b2d1c6316ba@syzkaller.appspotmail.com
Fixes: 6a21cc50f0 ("seccomp: add a return code to trap to userspace")
Signed-off-by: Tycho Andersen <tycho@tycho.ws>
Acked-by: Kees Cook <keescook@chromium.org>
Signed-off-by: James Morris <james.morris@microsoft.com>
This patch provides a general mechanism for passing flags to the
security_capable LSM hook. It replaces the specific 'audit' flag that is
used to tell security_capable whether it should log an audit message for
the given capability check. The reason for generalizing this flag
passing is so we can add an additional flag that signifies whether
security_capable is being called by a setid syscall (which is needed by
the proposed SafeSetID LSM).
Signed-off-by: Micah Morton <mortonm@chromium.org>
Reviewed-by: Kees Cook <keescook@chromium.org>
Signed-off-by: James Morris <james.morris@microsoft.com>
sparse complains,
kernel/seccomp.c:1172:13: warning: incorrect type in assignment (different base types)
kernel/seccomp.c:1172:13: expected restricted __poll_t [usertype] ret
kernel/seccomp.c:1172:13: got int
kernel/seccomp.c:1173:13: warning: restricted __poll_t degrades to integer
Instead of assigning this to ret, since we don't use this anywhere, let's
just test it against 0 directly.
Signed-off-by: Tycho Andersen <tycho@tycho.ws>
Reported-by: 0day robot <lkp@intel.com>
Fixes: 6a21cc50f0 ("seccomp: add a return code to trap to userspace")
Signed-off-by: Kees Cook <keescook@chromium.org>
This patch introduces a means for syscalls matched in seccomp to notify
some other task that a particular filter has been triggered.
The motivation for this is primarily for use with containers. For example,
if a container does an init_module(), we obviously don't want to load this
untrusted code, which may be compiled for the wrong version of the kernel
anyway. Instead, we could parse the module image, figure out which module
the container is trying to load and load it on the host.
As another example, containers cannot mount() in general since various
filesystems assume a trusted image. However, if an orchestrator knows that
e.g. a particular block device has not been exposed to a container for
writing, it want to allow the container to mount that block device (that
is, handle the mount for it).
This patch adds functionality that is already possible via at least two
other means that I know about, both of which involve ptrace(): first, one
could ptrace attach, and then iterate through syscalls via PTRACE_SYSCALL.
Unfortunately this is slow, so a faster version would be to install a
filter that does SECCOMP_RET_TRACE, which triggers a PTRACE_EVENT_SECCOMP.
Since ptrace allows only one tracer, if the container runtime is that
tracer, users inside the container (or outside) trying to debug it will not
be able to use ptrace, which is annoying. It also means that older
distributions based on Upstart cannot boot inside containers using ptrace,
since upstart itself uses ptrace to monitor services while starting.
The actual implementation of this is fairly small, although getting the
synchronization right was/is slightly complex.
Finally, it's worth noting that the classic seccomp TOCTOU of reading
memory data from the task still applies here, but can be avoided with
careful design of the userspace handler: if the userspace handler reads all
of the task memory that is necessary before applying its security policy,
the tracee's subsequent memory edits will not be read by the tracer.
Signed-off-by: Tycho Andersen <tycho@tycho.ws>
CC: Kees Cook <keescook@chromium.org>
CC: Andy Lutomirski <luto@amacapital.net>
CC: Oleg Nesterov <oleg@redhat.com>
CC: Eric W. Biederman <ebiederm@xmission.com>
CC: "Serge E. Hallyn" <serge@hallyn.com>
Acked-by: Serge Hallyn <serge@hallyn.com>
CC: Christian Brauner <christian@brauner.io>
CC: Tyler Hicks <tyhicks@canonical.com>
CC: Akihiro Suda <suda.akihiro@lab.ntt.co.jp>
Signed-off-by: Kees Cook <keescook@chromium.org>
The const qualifier causes problems for any code that wants to write to the
third argument of the seccomp syscall, as we will do in a future patch in
this series.
The third argument to the seccomp syscall is documented as void *, so
rather than just dropping the const, let's switch everything to use void *
as well.
I believe this is safe because of 1. the documentation above, 2. there's no
real type information exported about syscalls anywhere besides the man
pages.
Signed-off-by: Tycho Andersen <tycho@tycho.ws>
CC: Kees Cook <keescook@chromium.org>
CC: Andy Lutomirski <luto@amacapital.net>
CC: Oleg Nesterov <oleg@redhat.com>
CC: Eric W. Biederman <ebiederm@xmission.com>
CC: "Serge E. Hallyn" <serge@hallyn.com>
Acked-by: Serge Hallyn <serge@hallyn.com>
CC: Christian Brauner <christian@brauner.io>
CC: Tyler Hicks <tyhicks@canonical.com>
CC: Akihiro Suda <suda.akihiro@lab.ntt.co.jp>
Signed-off-by: Kees Cook <keescook@chromium.org>
In the next patch, we're going to use the sd pointer passed to
__seccomp_filter() as the data to pass to userspace. Except that in some
cases (__seccomp_filter(SECCOMP_RET_TRACE), emulate_vsyscall(), every time
seccomp is inovked on power, etc.) the sd pointer will be NULL in order to
force seccomp to recompute the register data. Previously this recomputation
happened one level lower, in seccomp_run_filters(); this patch just moves
it up a level higher to __seccomp_filter().
Thanks Oleg for spotting this.
Signed-off-by: Tycho Andersen <tycho@tycho.ws>
CC: Kees Cook <keescook@chromium.org>
CC: Andy Lutomirski <luto@amacapital.net>
CC: Oleg Nesterov <oleg@redhat.com>
CC: Eric W. Biederman <ebiederm@xmission.com>
CC: "Serge E. Hallyn" <serge@hallyn.com>
Acked-by: Serge Hallyn <serge@hallyn.com>
CC: Christian Brauner <christian@brauner.io>
CC: Tyler Hicks <tyhicks@canonical.com>
CC: Akihiro Suda <suda.akihiro@lab.ntt.co.jp>
Signed-off-by: Kees Cook <keescook@chromium.org>
Pull security subsystem updates from James Morris:
"In this patchset, there are a couple of minor updates, as well as some
reworking of the LSM initialization code from Kees Cook (these prepare
the way for ordered stackable LSMs, but are a valuable cleanup on
their own)"
* 'next-general' of git://git.kernel.org/pub/scm/linux/kernel/git/jmorris/linux-security:
LSM: Don't ignore initialization failures
LSM: Provide init debugging infrastructure
LSM: Record LSM name in struct lsm_info
LSM: Convert security_initcall() into DEFINE_LSM()
vmlinux.lds.h: Move LSM_TABLE into INIT_DATA
LSM: Convert from initcall to struct lsm_info
LSM: Remove initcall tracing
LSM: Rename .security_initcall section to .lsm_info
vmlinux.lds.h: Avoid copy/paste of security_init section
LSM: Correctly announce start of LSM initialization
security: fix LSM description location
keys: Fix the use of the C++ keyword "private" in uapi/linux/keyctl.h
seccomp: remove unnecessary unlikely()
security: tomoyo: Fix obsolete function
security/capabilities: remove check for -EINVAL
Linus recently observed that if we did not worry about the padding
member in struct siginfo it is only about 48 bytes, and 48 bytes is
much nicer than 128 bytes for allocating on the stack and copying
around in the kernel.
The obvious thing of only adding the padding when userspace is
including siginfo.h won't work as there are sigframe definitions in
the kernel that embed struct siginfo.
So split siginfo in two; kernel_siginfo and siginfo. Keeping the
traditional name for the userspace definition. While the version that
is used internally to the kernel and ultimately will not be padded to
128 bytes is called kernel_siginfo.
The definition of struct kernel_siginfo I have put in include/signal_types.h
A set of buildtime checks has been added to verify the two structures have
the same field offsets.
To make it easy to verify the change kernel_siginfo retains the same
size as siginfo. The reduction in size comes in a following change.
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
WARN_ON() already contains an unlikely(), so it's not necessary to wrap it
into another.
Signed-off-by: Igor Stoppa <igor.stoppa@huawei.com>
Acked-by: Kees Cook <keescook@chromium.org>
Cc: linux-security-module@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Signed-off-by: James Morris <james.morris@microsoft.com>
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Merge tag 'audit-pr-20180605' of git://git.kernel.org/pub/scm/linux/kernel/git/pcmoore/audit
Pull audit updates from Paul Moore:
"Another reasonable chunk of audit changes for v4.18, thirteen patches
in total.
The thirteen patches can mostly be broken down into one of four
categories: general bug fixes, accessor functions for audit state
stored in the task_struct, negative filter matches on executable
names, and extending the (relatively) new seccomp logging knobs to the
audit subsystem.
The main driver for the accessor functions from Richard are the
changes we're working on to associate audit events with containers,
but I think they have some standalone value too so I figured it would
be good to get them in now.
The seccomp/audit patches from Tyler apply the seccomp logging
improvements from a few releases ago to audit's seccomp logging;
starting with this patchset the changes in
/proc/sys/kernel/seccomp/actions_logged should apply to both the
standard kernel logging and audit.
As usual, everything passes the audit-testsuite and it happens to
merge cleanly with your tree"
[ Heh, except it had trivial merge conflicts with the SELinux tree that
also came in from Paul - Linus ]
* tag 'audit-pr-20180605' of git://git.kernel.org/pub/scm/linux/kernel/git/pcmoore/audit:
audit: Fix wrong task in comparison of session ID
audit: use existing session info function
audit: normalize loginuid read access
audit: use new audit_context access funciton for seccomp_actions_logged
audit: use inline function to set audit context
audit: use inline function to get audit context
audit: convert sessionid unset to a macro
seccomp: Don't special case audited processes when logging
seccomp: Audit attempts to modify the actions_logged sysctl
seccomp: Configurable separator for the actions_logged string
seccomp: Separate read and write code for actions_logged sysctl
audit: allow not equal op for audit by executable
audit: add syscall information to FEATURE_CHANGE records
Seccomp logging for "handled" actions such as RET_TRAP, RET_TRACE, or
RET_ERRNO can be very noisy for processes that are being audited. This
patch modifies the seccomp logging behavior to treat processes that are
being inspected via the audit subsystem the same as processes that
aren't under inspection. Handled actions will no longer be logged just
because the process is being inspected. Since v4.14, applications have
the ability to request logging of handled actions by using the
SECCOMP_FILTER_FLAG_LOG flag when loading seccomp filters.
With this patch, the logic for deciding if an action will be logged is:
if action == RET_ALLOW:
do not log
else if action not in actions_logged:
do not log
else if action == RET_KILL:
log
else if action == RET_LOG:
log
else if filter-requests-logging:
log
else:
do not log
Reported-by: Steve Grubb <sgrubb@redhat.com>
Signed-off-by: Tyler Hicks <tyhicks@canonical.com>
Acked-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Paul Moore <paul@paul-moore.com>
The decision to log a seccomp action will always be subject to the
value of the kernel.seccomp.actions_logged sysctl, even for processes
that are being inspected via the audit subsystem, in an upcoming patch.
Therefore, we need to emit an audit record on attempts at writing to the
actions_logged sysctl when auditing is enabled.
This patch updates the write handler for the actions_logged sysctl to
emit an audit record on attempts to write to the sysctl. Successful
writes to the sysctl will result in a record that includes a normalized
list of logged actions in the "actions" field and a "res" field equal to
1. Unsuccessful writes to the sysctl will result in a record that
doesn't include the "actions" field and has a "res" field equal to 0.
Not all unsuccessful writes to the sysctl are audited. For example, an
audit record will not be emitted if an unprivileged process attempts to
open the sysctl file for reading since that access control check is not
part of the sysctl's write handler.
Below are some example audit records when writing various strings to the
actions_logged sysctl.
Writing "not-a-real-action", when the kernel.seccomp.actions_logged
sysctl previously was "kill_process kill_thread trap errno trace log",
emits this audit record:
type=CONFIG_CHANGE msg=audit(1525392371.454:120): op=seccomp-logging
actions=? old-actions=kill_process,kill_thread,trap,errno,trace,log
res=0
If you then write "kill_process kill_thread errno trace log", this audit
record is emitted:
type=CONFIG_CHANGE msg=audit(1525392401.645:126): op=seccomp-logging
actions=kill_process,kill_thread,errno,trace,log
old-actions=kill_process,kill_thread,trap,errno,trace,log res=1
If you then write "log log errno trace kill_process kill_thread", which
is unordered and contains the log action twice, it results in the same
actions value as the previous record:
type=CONFIG_CHANGE msg=audit(1525392436.354:132): op=seccomp-logging
actions=kill_process,kill_thread,errno,trace,log
old-actions=kill_process,kill_thread,errno,trace,log res=1
If you then write an empty string to the sysctl, this audit record is
emitted:
type=CONFIG_CHANGE msg=audit(1525392494.413:138): op=seccomp-logging
actions=(none) old-actions=kill_process,kill_thread,errno,trace,log
res=1
No audit records are generated when reading the actions_logged sysctl.
Suggested-by: Steve Grubb <sgrubb@redhat.com>
Signed-off-by: Tyler Hicks <tyhicks@canonical.com>
Acked-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Paul Moore <paul@paul-moore.com>
The function that converts a bitmask of seccomp actions that are
allowed to be logged is currently only used for constructing the display
string for the kernel.seccomp.actions_logged sysctl. That string wants a
space character to be used for the separator between actions.
A future patch will make use of the same function for building a string
that will be sent to the audit subsystem for tracking modifications to
the kernel.seccomp.actions_logged sysctl. That string will need to use a
comma as a separator. This patch allows the separator character to be
configurable to meet both needs.
Signed-off-by: Tyler Hicks <tyhicks@canonical.com>
Acked-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Paul Moore <paul@paul-moore.com>
Break the read and write paths of the kernel.seccomp.actions_logged
sysctl into separate functions to maintain readability. An upcoming
change will need to audit writes, but not reads, of this sysctl which
would introduce too many conditional code paths on whether or not the
'write' parameter evaluates to true.
Signed-off-by: Tyler Hicks <tyhicks@canonical.com>
Acked-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Paul Moore <paul@paul-moore.com>
The migitation control is simpler to implement in architecture code as it
avoids the extra function call to check the mode. Aside of that having an
explicit seccomp enabled mode in the architecture mitigations would require
even more workarounds.
Move it into architecture code and provide a weak function in the seccomp
code. Remove the 'which' argument as this allows the architecture to decide
which mitigations are relevant for seccomp.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
If a seccomp user is not interested in Speculative Store Bypass mitigation
by default, it can set the new SECCOMP_FILTER_FLAG_SPEC_ALLOW flag when
adding filters.
Signed-off-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
When speculation flaw mitigations are opt-in (via prctl), using seccomp
will automatically opt-in to these protections, since using seccomp
indicates at least some level of sandboxing is desired.
Signed-off-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Previously if users passed a small size for the input structure size, they
would get get odd behavior. It doesn't make sense to pass a structure
smaller than at least filter_off size, so let's just give -EINVAL in this
case.
This changes userspace visible behavior, but was only introduced in commit
26500475ac ("ptrace, seccomp: add support for retrieving seccomp
metadata") in 4.16-rc2, so should be safe to change if merged before then.
Reported-by: Eugene Syromiatnikov <esyr@redhat.com>
Signed-off-by: Tycho Andersen <tycho@tycho.ws>
CC: Kees Cook <keescook@chromium.org>
CC: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Kees Cook <keescook@chromium.org>
Pull seccomp updates from James Morris:
"Add support for retrieving seccomp metadata"
* 'next-seccomp' of git://git.kernel.org/pub/scm/linux/kernel/git/jmorris/linux-security:
ptrace, seccomp: add support for retrieving seccomp metadata
seccomp: hoist out filter resolving logic
The function clear_siginfo is just a nice wrapper around memset so
this results in no functional change. This change makes mistakes
a little more difficult and it makes it clearer what is going on.
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
With the new SECCOMP_FILTER_FLAG_LOG, we need to be able to extract these
flags for checkpoint restore, since they describe the state of a filter.
So, let's add PTRACE_SECCOMP_GET_METADATA, similar to ..._GET_FILTER, which
returns the metadata of the nth filter (right now, just the flags).
Hopefully this will be future proof, and new per-filter metadata can be
added to this struct.
Signed-off-by: Tycho Andersen <tycho@docker.com>
CC: Kees Cook <keescook@chromium.org>
CC: Andy Lutomirski <luto@amacapital.net>
CC: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Kees Cook <keescook@chromium.org>
Hoist out the nth filter resolving logic that ptrace uses into a new
function. We'll use this in the next patch to implement the new
PTRACE_SECCOMP_GET_FILTER_FLAGS command.
Signed-off-by: Tycho Andersen <tycho@docker.com>
CC: Kees Cook <keescook@chromium.org>
CC: Andy Lutomirski <luto@amacapital.net>
CC: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Kees Cook <keescook@chromium.org>
Many source files in the tree are missing licensing information, which
makes it harder for compliance tools to determine the correct license.
By default all files without license information are under the default
license of the kernel, which is GPL version 2.
Update the files which contain no license information with the 'GPL-2.0'
SPDX license identifier. The SPDX identifier is a legally binding
shorthand, which can be used instead of the full boiler plate text.
This patch is based on work done by Thomas Gleixner and Kate Stewart and
Philippe Ombredanne.
How this work was done:
Patches were generated and checked against linux-4.14-rc6 for a subset of
the use cases:
- file had no licensing information it it.
- file was a */uapi/* one with no licensing information in it,
- file was a */uapi/* one with existing licensing information,
Further patches will be generated in subsequent months to fix up cases
where non-standard license headers were used, and references to license
had to be inferred by heuristics based on keywords.
The analysis to determine which SPDX License Identifier to be applied to
a file was done in a spreadsheet of side by side results from of the
output of two independent scanners (ScanCode & Windriver) producing SPDX
tag:value files created by Philippe Ombredanne. Philippe prepared the
base worksheet, and did an initial spot review of a few 1000 files.
The 4.13 kernel was the starting point of the analysis with 60,537 files
assessed. Kate Stewart did a file by file comparison of the scanner
results in the spreadsheet to determine which SPDX license identifier(s)
to be applied to the file. She confirmed any determination that was not
immediately clear with lawyers working with the Linux Foundation.
Criteria used to select files for SPDX license identifier tagging was:
- Files considered eligible had to be source code files.
- Make and config files were included as candidates if they contained >5
lines of source
- File already had some variant of a license header in it (even if <5
lines).
All documentation files were explicitly excluded.
The following heuristics were used to determine which SPDX license
identifiers to apply.
- when both scanners couldn't find any license traces, file was
considered to have no license information in it, and the top level
COPYING file license applied.
For non */uapi/* files that summary was:
SPDX license identifier # files
---------------------------------------------------|-------
GPL-2.0 11139
and resulted in the first patch in this series.
If that file was a */uapi/* path one, it was "GPL-2.0 WITH
Linux-syscall-note" otherwise it was "GPL-2.0". Results of that was:
SPDX license identifier # files
---------------------------------------------------|-------
GPL-2.0 WITH Linux-syscall-note 930
and resulted in the second patch in this series.
- if a file had some form of licensing information in it, and was one
of the */uapi/* ones, it was denoted with the Linux-syscall-note if
any GPL family license was found in the file or had no licensing in
it (per prior point). Results summary:
SPDX license identifier # files
---------------------------------------------------|------
GPL-2.0 WITH Linux-syscall-note 270
GPL-2.0+ WITH Linux-syscall-note 169
((GPL-2.0 WITH Linux-syscall-note) OR BSD-2-Clause) 21
((GPL-2.0 WITH Linux-syscall-note) OR BSD-3-Clause) 17
LGPL-2.1+ WITH Linux-syscall-note 15
GPL-1.0+ WITH Linux-syscall-note 14
((GPL-2.0+ WITH Linux-syscall-note) OR BSD-3-Clause) 5
LGPL-2.0+ WITH Linux-syscall-note 4
LGPL-2.1 WITH Linux-syscall-note 3
((GPL-2.0 WITH Linux-syscall-note) OR MIT) 3
((GPL-2.0 WITH Linux-syscall-note) AND MIT) 1
and that resulted in the third patch in this series.
- when the two scanners agreed on the detected license(s), that became
the concluded license(s).
- when there was disagreement between the two scanners (one detected a
license but the other didn't, or they both detected different
licenses) a manual inspection of the file occurred.
- In most cases a manual inspection of the information in the file
resulted in a clear resolution of the license that should apply (and
which scanner probably needed to revisit its heuristics).
- When it was not immediately clear, the license identifier was
confirmed with lawyers working with the Linux Foundation.
- If there was any question as to the appropriate license identifier,
the file was flagged for further research and to be revisited later
in time.
In total, over 70 hours of logged manual review was done on the
spreadsheet to determine the SPDX license identifiers to apply to the
source files by Kate, Philippe, Thomas and, in some cases, confirmation
by lawyers working with the Linux Foundation.
Kate also obtained a third independent scan of the 4.13 code base from
FOSSology, and compared selected files where the other two scanners
disagreed against that SPDX file, to see if there was new insights. The
Windriver scanner is based on an older version of FOSSology in part, so
they are related.
Thomas did random spot checks in about 500 files from the spreadsheets
for the uapi headers and agreed with SPDX license identifier in the
files he inspected. For the non-uapi files Thomas did random spot checks
in about 15000 files.
In initial set of patches against 4.14-rc6, 3 files were found to have
copy/paste license identifier errors, and have been fixed to reflect the
correct identifier.
Additionally Philippe spent 10 hours this week doing a detailed manual
inspection and review of the 12,461 patched files from the initial patch
version early this week with:
- a full scancode scan run, collecting the matched texts, detected
license ids and scores
- reviewing anything where there was a license detected (about 500+
files) to ensure that the applied SPDX license was correct
- reviewing anything where there was no detection but the patch license
was not GPL-2.0 WITH Linux-syscall-note to ensure that the applied
SPDX license was correct
This produced a worksheet with 20 files needing minor correction. This
worksheet was then exported into 3 different .csv files for the
different types of files to be modified.
These .csv files were then reviewed by Greg. Thomas wrote a script to
parse the csv files and add the proper SPDX tag to the file, in the
format that the file expected. This script was further refined by Greg
based on the output to detect more types of files automatically and to
distinguish between header and source .c files (which need different
comment types.) Finally Greg ran the script using the .csv files to
generate the patches.
Reviewed-by: Kate Stewart <kstewart@linuxfoundation.org>
Reviewed-by: Philippe Ombredanne <pombredanne@nexb.com>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
READ_ONCE() now has an implicit smp_read_barrier_depends() call, so it
can be used instead of lockless_dereference() without any change in
semantics.
Signed-off-by: Will Deacon <will.deacon@arm.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/1508840570-22169-4-git-send-email-will.deacon@arm.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
The function __get_seccomp_filter is local to the source and does
not need to be in global scope, so make it static.
Cleans up sparse warning:
symbol '__get_seccomp_filter' was not declared. Should it be static?
Signed-off-by: Colin Ian King <colin.king@canonical.com>
Fixes: 66a733ea6b ("seccomp: fix the usage of get/put_seccomp_filter() in seccomp_get_filter()")
Cc: stable@vger.kernel.org
Signed-off-by: Kees Cook <keescook@chromium.org>
As Chris explains, get_seccomp_filter() and put_seccomp_filter() can end
up using different filters. Once we drop ->siglock it is possible for
task->seccomp.filter to have been replaced by SECCOMP_FILTER_FLAG_TSYNC.
Fixes: f8e529ed94 ("seccomp, ptrace: add support for dumping seccomp filters")
Reported-by: Chris Salls <chrissalls5@gmail.com>
Cc: stable@vger.kernel.org # needs s/refcount_/atomic_/ for v4.12 and earlier
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
[tycho: add __get_seccomp_filter vs. open coding refcount_inc()]
Signed-off-by: Tycho Andersen <tycho@docker.com>
[kees: tweak commit log]
Signed-off-by: Kees Cook <keescook@chromium.org>
Right now, SECCOMP_RET_KILL_THREAD (neé SECCOMP_RET_KILL) kills the
current thread. There have been a few requests for this to kill the entire
process (the thread group). This cannot be just changed (discovered when
adding coredump support since coredumping kills the entire process)
because there are userspace programs depending on the thread-kill
behavior.
Instead, implement SECCOMP_RET_KILL_PROCESS, which is 0x80000000, and can
be processed as "-1" by the kernel, below the existing RET_KILL that is
ABI-set to "0". For userspace, SECCOMP_RET_ACTION_FULL is added to expand
the mask to the signed bit. Old userspace using the SECCOMP_RET_ACTION
mask will see SECCOMP_RET_KILL_PROCESS as 0 still, but this would only
be visible when examining the siginfo in a core dump from a RET_KILL_*,
where it will think it was thread-killed instead of process-killed.
Attempts to introduce this behavior via other ways (filter flags,
seccomp struct flags, masked RET_DATA bits) all come with weird
side-effects and baggage. This change preserves the central behavioral
expectations of the seccomp filter engine without putting too great
a burden on changes needed in userspace to use the new action.
The new action is discoverable by userspace through either the new
actions_avail sysctl or through the SECCOMP_GET_ACTION_AVAIL seccomp
operation. If used without checking for availability, old kernels
will treat RET_KILL_PROCESS as RET_KILL_THREAD (since the old mask
will produce RET_KILL_THREAD).
Cc: Paul Moore <paul@paul-moore.com>
Cc: Fabricio Voznika <fvoznika@google.com>
Signed-off-by: Kees Cook <keescook@chromium.org>
This introduces the BPF return value for SECCOMP_RET_KILL_PROCESS to kill
an entire process. This cannot yet be reached by seccomp, but it changes
the default-kill behavior (for unknown return values) from kill-thread to
kill-process.
Signed-off-by: Kees Cook <keescook@chromium.org>
In preparation for adding SECCOMP_RET_KILL_PROCESS, rename SECCOMP_RET_KILL
to the more accurate SECCOMP_RET_KILL_THREAD.
The existing selftest values are intentionally left as SECCOMP_RET_KILL
just to be sure we're exercising the alias.
Signed-off-by: Kees Cook <keescook@chromium.org>
Add a new action, SECCOMP_RET_LOG, that logs a syscall before allowing
the syscall. At the implementation level, this action is identical to
the existing SECCOMP_RET_ALLOW action. However, it can be very useful when
initially developing a seccomp filter for an application. The developer
can set the default action to be SECCOMP_RET_LOG, maybe mark any
obviously needed syscalls with SECCOMP_RET_ALLOW, and then put the
application through its paces. A list of syscalls that triggered the
default action (SECCOMP_RET_LOG) can be easily gleaned from the logs and
that list can be used to build the syscall whitelist. Finally, the
developer can change the default action to the desired value.
This provides a more friendly experience than seeing the application get
killed, then updating the filter and rebuilding the app, seeing the
application get killed due to a different syscall, then updating the
filter and rebuilding the app, etc.
The functionality is similar to what's supported by the various LSMs.
SELinux has permissive mode, AppArmor has complain mode, SMACK has
bring-up mode, etc.
SECCOMP_RET_LOG is given a lower value than SECCOMP_RET_ALLOW as allow
while logging is slightly more restrictive than quietly allowing.
Unfortunately, the tests added for SECCOMP_RET_LOG are not capable of
inspecting the audit log to verify that the syscall was logged.
With this patch, the logic for deciding if an action will be logged is:
if action == RET_ALLOW:
do not log
else if action == RET_KILL && RET_KILL in actions_logged:
log
else if action == RET_LOG && RET_LOG in actions_logged:
log
else if filter-requests-logging && action in actions_logged:
log
else if audit_enabled && process-is-being-audited:
log
else:
do not log
Signed-off-by: Tyler Hicks <tyhicks@canonical.com>
Signed-off-by: Kees Cook <keescook@chromium.org>
Add a new filter flag, SECCOMP_FILTER_FLAG_LOG, that enables logging for
all actions except for SECCOMP_RET_ALLOW for the given filter.
SECCOMP_RET_KILL actions are always logged, when "kill" is in the
actions_logged sysctl, and SECCOMP_RET_ALLOW actions are never logged,
regardless of this flag.
This flag can be used to create noisy filters that result in all
non-allowed actions to be logged. A process may have one noisy filter,
which is loaded with this flag, as well as a quiet filter that's not
loaded with this flag. This allows for the actions in a set of filters
to be selectively conveyed to the admin.
Since a system could have a large number of allocated seccomp_filter
structs, struct packing was taken in consideration. On 64 bit x86, the
new log member takes up one byte of an existing four byte hole in the
struct. On 32 bit x86, the new log member creates a new four byte hole
(unavoidable) and consumes one of those bytes.
Unfortunately, the tests added for SECCOMP_FILTER_FLAG_LOG are not
capable of inspecting the audit log to verify that the actions taken in
the filter were logged.
With this patch, the logic for deciding if an action will be logged is:
if action == RET_ALLOW:
do not log
else if action == RET_KILL && RET_KILL in actions_logged:
log
else if filter-requests-logging && action in actions_logged:
log
else if audit_enabled && process-is-being-audited:
log
else:
do not log
Signed-off-by: Tyler Hicks <tyhicks@canonical.com>
Signed-off-by: Kees Cook <keescook@chromium.org>
Adminstrators can write to this sysctl to set the seccomp actions that
are allowed to be logged. Any actions not found in this sysctl will not
be logged.
For example, all SECCOMP_RET_KILL, SECCOMP_RET_TRAP, and
SECCOMP_RET_ERRNO actions would be loggable if "kill trap errno" were
written to the sysctl. SECCOMP_RET_TRACE actions would not be logged
since its string representation ("trace") wasn't present in the sysctl
value.
The path to the sysctl is:
/proc/sys/kernel/seccomp/actions_logged
The actions_avail sysctl can be read to discover the valid action names
that can be written to the actions_logged sysctl with the exception of
"allow". SECCOMP_RET_ALLOW actions cannot be configured for logging.
The default setting for the sysctl is to allow all actions to be logged
except SECCOMP_RET_ALLOW. While only SECCOMP_RET_KILL actions are
currently logged, an upcoming patch will allow applications to request
additional actions to be logged.
There's one important exception to this sysctl. If a task is
specifically being audited, meaning that an audit context has been
allocated for the task, seccomp will log all actions other than
SECCOMP_RET_ALLOW despite the value of actions_logged. This exception
preserves the existing auditing behavior of tasks with an allocated
audit context.
With this patch, the logic for deciding if an action will be logged is:
if action == RET_ALLOW:
do not log
else if action == RET_KILL && RET_KILL in actions_logged:
log
else if audit_enabled && task-is-being-audited:
log
else:
do not log
Signed-off-by: Tyler Hicks <tyhicks@canonical.com>
Signed-off-by: Kees Cook <keescook@chromium.org>
Userspace code that needs to check if the kernel supports a given action
may not be able to use the /proc/sys/kernel/seccomp/actions_avail
sysctl. The process may be running in a sandbox and, therefore,
sufficient filesystem access may not be available. This patch adds an
operation to the seccomp(2) syscall that allows userspace code to ask
the kernel if a given action is available.
If the action is supported by the kernel, 0 is returned. If the action
is not supported by the kernel, -1 is returned with errno set to
-EOPNOTSUPP. If this check is attempted on a kernel that doesn't support
this new operation, -1 is returned with errno set to -EINVAL meaning
that userspace code will have the ability to differentiate between the
two error cases.
Signed-off-by: Tyler Hicks <tyhicks@canonical.com>
Suggested-by: Andy Lutomirski <luto@amacapital.net>
Signed-off-by: Kees Cook <keescook@chromium.org>
This patch creates a read-only sysctl containing an ordered list of
seccomp actions that the kernel supports. The ordering, from left to
right, is the lowest action value (kill) to the highest action value
(allow). Currently, a read of the sysctl file would return "kill trap
errno trace allow". The contents of this sysctl file can be useful for
userspace code as well as the system administrator.
The path to the sysctl is:
/proc/sys/kernel/seccomp/actions_avail
libseccomp and other userspace code can easily determine which actions
the current kernel supports. The set of actions supported by the current
kernel may be different than the set of action macros found in kernel
headers that were installed where the userspace code was built.
In addition, this sysctl will allow system administrators to know which
actions are supported by the kernel and make it easier to configure
exactly what seccomp logs through the audit subsystem. Support for this
level of logging configuration will come in a future patch.
Signed-off-by: Tyler Hicks <tyhicks@canonical.com>
Signed-off-by: Kees Cook <keescook@chromium.org>
Sargun Dhillon