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commit b805aebd42364fe696e417808a700fdb9800c9e8
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Author: Nikita Popov <npv1310@gmail.com>
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Date: Mon Aug 9 20:17:34 2021 +0530
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librt: fix NULL pointer dereference (bug 28213)
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Helper thread frees copied attribute on NOTIFY_REMOVED message
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received from the OS kernel. Unfortunately, it fails to check whether
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copied attribute actually exists (data.attr != NULL). This worked
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earlier because free() checks passed pointer before actually
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attempting to release corresponding memory. But
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__pthread_attr_destroy assumes pointer is not NULL.
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So passing NULL pointer to __pthread_attr_destroy will result in
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segmentation fault. This scenario is possible if
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notification->sigev_notify_attributes == NULL (which means default
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thread attributes should be used).
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Signed-off-by: Nikita Popov <npv1310@gmail.com>
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Reviewed-by: Siddhesh Poyarekar <siddhesh@sourceware.org>
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diff --git a/sysdeps/unix/sysv/linux/mq_notify.c b/sysdeps/unix/sysv/linux/mq_notify.c
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index 45449571d14c379f..581959d621135fb0 100644
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--- a/sysdeps/unix/sysv/linux/mq_notify.c
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+++ b/sysdeps/unix/sysv/linux/mq_notify.c
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@@ -134,7 +134,7 @@ helper_thread (void *arg)
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to wait until it is done with it. */
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(void) __pthread_barrier_wait (¬ify_barrier);
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}
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- else if (data.raw[NOTIFY_COOKIE_LEN - 1] == NOTIFY_REMOVED)
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+ else if (data.raw[NOTIFY_COOKIE_LEN - 1] == NOTIFY_REMOVED && data.attr != NULL)
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{
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/* The only state we keep is the copy of the thread attributes. */
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pthread_attr_destroy (data.attr);
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