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authorTorvald Riegel <triegel@redhat.com>2016-12-21 13:37:19 +0100
committerTorvald Riegel <triegel@redhat.com>2017-01-13 17:17:38 +0100
commit8e31cafb268938729a1314806a924d73fb1991c5 (patch)
treed58fa0d10a2a6eff2e8f3a5a775fa4fa1abdf271 /sysdeps
parent65810f0ef05e8c9e333f17a44e77808b163ca298 (diff)
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Clear list of acquired robust mutexes in the child process after forking.
Robust mutexes acquired at the time of a call to fork() do not remain acquired by the forked child process. We have to clear the list of acquired robust mutexes before registering this list with the kernel; otherwise, if some of the robust mutexes are process-shared, the parent process can alter the child's robust mutex list, which can lead to deadlocks or even modification of memory that may not be occupied by a mutex anymore. [BZ #19402] * sysdeps/nptl/fork.c (__libc_fork): Clear list of acquired robust mutexes.
Diffstat (limited to 'sysdeps')
-rw-r--r--sysdeps/nptl/fork.c20
1 files changed, 14 insertions, 6 deletions
diff --git a/sysdeps/nptl/fork.c b/sysdeps/nptl/fork.c
index 72fa82a47b..db6d721fce 100644
--- a/sysdeps/nptl/fork.c
+++ b/sysdeps/nptl/fork.c
@@ -162,12 +162,20 @@ __libc_fork (void)
#endif
#ifdef __NR_set_robust_list
- /* Initialize the robust mutex list which has been reset during
- the fork. We do not check for errors since if it fails here
- it failed at process start as well and noone could have used
- robust mutexes. We also do not have to set
- self->robust_head.futex_offset since we inherit the correct
- value from the parent. */
+ /* Initialize the robust mutex list setting in the kernel which has
+ been reset during the fork. We do not check for errors because if
+ it fails here, it must have failed at process startup as well and
+ nobody could have used robust mutexes.
+ Before we do that, we have to clear the list of robust mutexes
+ because we do not inherit ownership of mutexes from the parent.
+ We do not have to set self->robust_head.futex_offset since we do
+ inherit the correct value from the parent. We do not need to clear
+ the pending operation because it must have been zero when fork was
+ called. */
+# ifdef __PTHREAD_MUTEX_HAVE_PREV
+ self->robust_prev = &self->robust_head;
+# endif
+ self->robust_head.list = &self->robust_head;
# ifdef SHARED
if (__builtin_expect (__libc_pthread_functions_init, 0))
PTHFCT_CALL (ptr_set_robust, (self));