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ptrace, seccomp: add support for retrieving seccomp metadata 

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>
This commit is contained in:
Tycho Andersen 2017-10-11 09:39:21 -06:00 committed by Kees Cook
parent f06eae831f
commit 26500475ac
4 changed files with 51 additions and 0 deletions
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8
include/linux/seccomp.h
View File

@ -95,11 +95,19 @@ static inline void get_seccomp_filter(struct task_struct *tsk)
#if defined(CONFIG_SECCOMP_FILTER) && defined(CONFIG_CHECKPOINT_RESTORE)
extern long seccomp_get_filter(struct task_struct *task,
unsigned long filter_off, void __user *data);
extern long seccomp_get_metadata(struct task_struct *task,
unsigned long filter_off, void __user *data);
#else
static inline long seccomp_get_filter(struct task_struct *task,
unsigned long n, void __user *data)
{
return -EINVAL;
}
static inline long seccomp_get_metadata(struct task_struct *task,
unsigned long filter_off,
void __user *data)
{
return -EINVAL;
}
#endif /* CONFIG_SECCOMP_FILTER && CONFIG_CHECKPOINT_RESTORE */
#endif /* _LINUX_SECCOMP_H */

6
include/uapi/linux/ptrace.h
View File

@ -66,6 +66,12 @@ struct ptrace_peeksiginfo_args {
#define PTRACE_SETSIGMASK 0x420b
#define PTRACE_SECCOMP_GET_FILTER 0x420c
#define PTRACE_SECCOMP_GET_METADATA 0x420d
struct seccomp_metadata {
unsigned long filter_off; /* Input: which filter */
unsigned int flags; /* Output: filter's flags */
};
/* Read signals from a shared (process wide) queue */
#define PTRACE_PEEKSIGINFO_SHARED (1 << 0)

4
kernel/ptrace.c
View File

@ -1092,6 +1092,10 @@ int ptrace_request(struct task_struct *child, long request,
ret = seccomp_get_filter(child, addr, datavp);
break;
case PTRACE_SECCOMP_GET_METADATA:
ret = seccomp_get_metadata(child, addr, datavp);
break;
default:
break;
}

33
kernel/seccomp.c
View File

@ -1061,6 +1061,39 @@ long seccomp_get_filter(struct task_struct *task, unsigned long filter_off,
__put_seccomp_filter(filter);
return ret;
}
long seccomp_get_metadata(struct task_struct *task,
unsigned long size, void __user *data)
{
long ret;
struct seccomp_filter *filter;
struct seccomp_metadata kmd = {};
if (!capable(CAP_SYS_ADMIN) ||
current->seccomp.mode != SECCOMP_MODE_DISABLED) {
return -EACCES;
}
size = min_t(unsigned long, size, sizeof(kmd));
if (copy_from_user(&kmd, data, size))
return -EFAULT;
filter = get_nth_filter(task, kmd.filter_off);
if (IS_ERR(filter))
return PTR_ERR(filter);
memset(&kmd, 0, sizeof(kmd));
if (filter->log)
kmd.flags |= SECCOMP_FILTER_FLAG_LOG;
ret = size;
if (copy_to_user(data, &kmd, size))
ret = -EFAULT;
__put_seccomp_filter(filter);
return ret;
}
#endif
#ifdef CONFIG_SYSCTL