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Eric Blake 65b0ee31b1 util: make virSetUIDGID async-signal-safe 
https://bugzilla.redhat.com/show_bug.cgi?id=964358

POSIX states that multi-threaded apps should not use functions
that are not async-signal-safe between fork and exec, yet we
were using getpwuid_r and initgroups.  Although rare, it is
possible to hit deadlock in the child, when it tries to grab
a mutex that was already held by another thread in the parent.
I actually hit this deadlock when testing multiple domains
being started in parallel with a command hook, with the following
backtrace in the child:

 Thread 1 (Thread 0x7fd56bbf2700 (LWP 3212)):
 #0  __lll_lock_wait ()
     at ../nptl/sysdeps/unix/sysv/linux/x86_64/lowlevellock.S:136
 #1  0x00007fd5761e7388 in _L_lock_854 () from /lib64/libpthread.so.0
 #2  0x00007fd5761e7257 in __pthread_mutex_lock (mutex=0x7fd56be00360)
     at pthread_mutex_lock.c:61
 #3  0x00007fd56bbf9fc5 in _nss_files_getpwuid_r (uid=0, result=0x7fd56bbf0c70,
     buffer=0x7fd55c2a65f0 "", buflen=1024, errnop=0x7fd56bbf25b8)
     at nss_files/files-pwd.c:40
 #4  0x00007fd575aeff1d in __getpwuid_r (uid=0, resbuf=0x7fd56bbf0c70,
     buffer=0x7fd55c2a65f0 "", buflen=1024, result=0x7fd56bbf0cb0)
     at ../nss/getXXbyYY_r.c:253
 #5  0x00007fd578aebafc in virSetUIDGID (uid=0, gid=0) at util/virutil.c:1031
 #6  0x00007fd578aebf43 in virSetUIDGIDWithCaps (uid=0, gid=0, capBits=0,
     clearExistingCaps=true) at util/virutil.c:1388
 #7  0x00007fd578a9a20b in virExec (cmd=0x7fd55c231f10) at util/vircommand.c:654
 #8  0x00007fd578a9dfa2 in virCommandRunAsync (cmd=0x7fd55c231f10, pid=0x0)
     at util/vircommand.c:2247
 #9  0x00007fd578a9d74e in virCommandRun (cmd=0x7fd55c231f10, exitstatus=0x0)
     at util/vircommand.c:2100
 #10 0x00007fd56326fde5 in qemuProcessStart (conn=0x7fd53c000df0,
     driver=0x7fd55c0dc4f0, vm=0x7fd54800b100, migrateFrom=0x0, stdin_fd=-1,
     stdin_path=0x0, snapshot=0x0, vmop=VIR_NETDEV_VPORT_PROFILE_OP_CREATE,
     flags=1) at qemu/qemu_process.c:3694
 ...

The solution is to split the work of getpwuid_r/initgroups into the
unsafe portions (getgrouplist, called pre-fork) and safe portions
(setgroups, called post-fork).

* src/util/virutil.h (virSetUIDGID, virSetUIDGIDWithCaps): Adjust
signature.
* src/util/virutil.c (virSetUIDGID): Add parameters.
(virSetUIDGIDWithCaps): Adjust clients.
* src/util/vircommand.c (virExec): Likewise.
* src/util/virfile.c (virFileAccessibleAs, virFileOpenForked)
(virDirCreate): Likewise.
* src/security/security_dac.c (virSecurityDACSetProcessLabel):
Likewise.
* src/lxc/lxc_container.c (lxcContainerSetID): Likewise.
* configure.ac (AC_CHECK_FUNCS_ONCE): Check for setgroups, not
initgroups.

Signed-off-by: Eric Blake <eblake@redhat.com>
(cherry picked from commit ee777e9949)

Conflicts:
	src/lxc/lxc_container.c - did not use setUIDGID before 1.1.0
	src/util/virutil.c - oom handling changes not backported; no virSetUIDGIDWithCaps
	src/util/virfile.c - functions still lived in virutil.c this far back
	configure.ac - context with previous commit
	src/util/command.c - no UID/GID handling in vircommand.c...
	src/storage/storage_backend.c - ...so do it in the one hook user instead
 		2013-07-22 16:48:37 -06:00
.gnulib@b4938324b7 build: avoid infinite autogen loop 2012-10-27 15:06:31 -04:00
build-aux maint: fix up copyright notice inconsistencies 2012-09-20 16:30:55 -06:00
daemon Tweak EOF handling of streams 2013-06-11 18:28:23 -04:00
docs Convert libxl driver to Xen 4.2 2013-01-07 10:40:02 -07:00
examples maint: fix up copyright notice inconsistencies 2012-09-20 16:30:55 -06:00
gnulib build: fix fresh checkout on RHEL5 2012-04-19 17:11:43 -06:00
include maint: fix up copyright notice inconsistencies 2012-09-20 16:30:55 -06:00
m4 build: avoid -Wno-format on new-enough gcc 2012-10-18 13:11:29 -04:00
po Prep for release 0.10.2.6 2013-06-12 17:06:18 -04:00
python Properly parse (unsigned) long long 2012-10-18 13:19:51 -04:00
src util: make virSetUIDGID async-signal-safe 2013-07-22 16:48:37 -06:00
tests smartcard: spell ccid-card-emulated qemu property correctly 2013-06-11 16:51:18 -04:00
tools virsh: edit: don't leak XML string on reedit or redefine 2013-06-26 17:43:28 +02:00
.dir-locals.el build: avoid tabs that failed syntax-check 2012-09-06 09:43:46 -06:00
.gitignore tools: Only install guests init script if --with-init=script=redhat 2013-01-07 11:26:52 -07:00
.gitmodules make .gnulib a submodule 2009-07-08 16:17:51 +02:00
.mailmap Autogenerate AUTHORS 2012-10-27 15:07:44 -04:00
AUTHORS.in Doug Goldstein gained commit capability 2012-12-09 16:28:00 -05:00
COPYING.LIB remove all trailing blank lines 2009-07-16 15:06:42 +02:00
ChangeLog-old virterror.c: Fix several spelling mistakes 2012-02-03 11:32:51 -07:00
HACKING Update how to compile with -Werror 2012-10-17 16:18:22 -04:00
Makefile.am Autogenerate AUTHORS 2012-10-27 15:07:44 -04:00
Makefile.nonreentrant Ban use of all inet_* functions 2010-10-22 11:59:23 +01:00
README Correct typos in the documentation (Atsushi SAKAI) 2008-01-24 10:15:13 +00:00
README-hacking maint: relax git minimum version 2010-02-24 14:29:27 -05:00
TODO Update todo list file to point at bugzilla/website 2010-10-13 16:45:26 +01:00
autobuild.sh Switch automated builds to use Mingw64 toolchain instead of Mingw32 2012-06-25 10:41:10 +01:00
autogen.sh build: fix incremental autogen.sh when no AUTHORS is present 2012-12-09 16:53:41 -05:00
bootstrap maint: regenerate bootstrap 2012-07-27 09:34:04 -06:00
bootstrap.conf Autogenerate AUTHORS 2012-10-27 15:07:44 -04:00
cfg.mk build: fix incremental autogen.sh when no AUTHORS is present 2012-12-09 16:53:41 -05:00
configure.ac util: make virSetUIDGID async-signal-safe 2013-07-22 16:48:37 -06:00
libvirt.pc.in build: silence warning from autoconf 2012-05-30 09:22:02 -06:00
libvirt.spec.in Prep for release 0.10.2.6 2013-06-12 17:06:18 -04:00
mingw-libvirt.spec.in parallels: add driver skeleton 2012-08-01 11:44:26 +08:00
run.in syntax-check: fix run.in 2012-09-18 13:59:53 +02:00

README 

         LibVirt : simple API for virtualization

  Libvirt is a C toolkit to interact with the virtualization capabilities
of recent versions of Linux (and other OSes). It is free software
available under the GNU Lesser General Public License. Virtualization of
the Linux Operating System means the ability to run multiple instances of
Operating Systems concurrently on a single hardware system where the basic
resources are driven by a Linux instance. The library aim at providing
long term stable C API initially for the Xen paravirtualization but
should be able to integrate other virtualization mechanisms if needed.

Daniel Veillard <veillard@redhat.com>