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Commit cbcf0112 authored by Miklos Szeredi's avatar Miklos Szeredi Committed by Linus Torvalds
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af_unix: fix garbage collect vs MSG_PEEK



unix_gc() assumes that candidate sockets can never gain an external
reference (i.e.  be installed into an fd) while the unix_gc_lock is
held.  Except for MSG_PEEK this is guaranteed by modifying inflight
count under the unix_gc_lock.

MSG_PEEK does not touch any variable protected by unix_gc_lock (file
count is not), yet it needs to be serialized with garbage collection.
Do this by locking/unlocking unix_gc_lock:

 1) increment file count

 2) lock/unlock barrier to make sure incremented file count is visible
    to garbage collection

 3) install file into fd

This is a lock barrier (unlike smp_mb()) that ensures that garbage
collection is run completely before or completely after the barrier.

Cc: <stable@vger.kernel.org>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: default avatarMiklos Szeredi <mszeredi@redhat.com>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 7d549995
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