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librt: fix NULL pointer dereference (bug 28213)

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Helper thread frees copied attribute on NOTIFY_REMOVED message
received from the OS kernel.  Unfortunately, it fails to check whether
copied attribute actually exists (data.attr != NULL).  This worked
earlier because free() checks passed pointer before actually
attempting to release corresponding memory.  But
__pthread_attr_destroy assumes pointer is not NULL.

So passing NULL pointer to __pthread_attr_destroy will result in
segmentation fault.  This scenario is possible if
notification->sigev_notify_attributes == NULL (which means default
thread attributes should be used).

Signed-off-by: Nikita Popov <npv1310@gmail.com>
Reviewed-by: Siddhesh Poyarekar <siddhesh@sourceware.org>
This commit is contained in:
Nikita Popov 2021-08-09 20:17:34 +05:30 committed by Siddhesh Poyarekar
parent 60b4dd2579
commit b805aebd42
1 changed files with 1 additions and 1 deletions
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2
sysdeps/unix/sysv/linux/mq_notify.c
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@ -131,7 +131,7 @@ helper_thread (void *arg)
to wait until it is done with it. */
(void) __pthread_barrier_wait (&notify_barrier);
}
else if (data.raw[NOTIFY_COOKIE_LEN - 1] == NOTIFY_REMOVED)
else if (data.raw[NOTIFY_COOKIE_LEN - 1] == NOTIFY_REMOVED && data.attr != NULL)
{
/* The only state we keep is the copy of the thread attributes. */
__pthread_attr_destroy (data.attr);