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authorEric Dumazet <eric.dumazet@gmail.com>2013-05-01 05:24:03 +0000
committerDavid S. Miller <davem@davemloft.net>2013-05-01 15:13:49 -0400
commit60bc851ae59bfe99be6ee89d6bc50008c85ec75d (patch)
tree5046b97e73431933b0205f5b9381fe09979ef2f4 /net/sctp
parentc3b28ea36946a22469a5519977a3b79428ded4af (diff)
downloadlinux-60bc851ae59bfe99be6ee89d6bc50008c85ec75d.tar.gz
af_unix: fix a fatal race with bit fields
Using bit fields is dangerous on ppc64/sparc64, as the compiler [1] uses 64bit instructions to manipulate them. If the 64bit word includes any atomic_t or spinlock_t, we can lose critical concurrent changes. This is happening in af_unix, where unix_sk(sk)->gc_candidate/ gc_maybe_cycle/lock share the same 64bit word. This leads to fatal deadlock, as one/several cpus spin forever on a spinlock that will never be available again. A safer way would be to use a long to store flags. This way we are sure compiler/arch wont do bad things. As we own unix_gc_lock spinlock when clearing or setting bits, we can use the non atomic __set_bit()/__clear_bit(). recursion_level can share the same 64bit location with the spinlock, as it is set only with this spinlock held. [1] bug fixed in gcc-4.8.0 : http://gcc.gnu.org/bugzilla/show_bug.cgi?id=52080 Reported-by: Ambrose Feinstein <ambrose@google.com> Signed-off-by: Eric Dumazet <edumazet@google.com> Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org> Cc: Paul Mackerras <paulus@samba.org> Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net/sctp')
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