CVE request: kernel: udp: Wrong locking code in udp seq_file infrastructure

[Eugene Teo <eugene () redhat com>]

According to the upstream commit 30842f298, reading zero bytes from
/proc/net/udp or other similar files which use the same seq_file udp
infrastructure panics kernel in that way:

=====================================
[ BUG: bad unlock balance detected! ]
-------------------------------------
read/1985 is trying to release lock (&table->hash[i].lock) at:
[<ffffffff81321d83>] udp_seq_stop+0x27/0x29
but there are no more locks to release!
[...]

This bug was introduced and fixed within a short timeframe. It was
introduced in 645ca708 (Follows: v2.6.28-rc2; Precedes: v2.6.29-rc1).

http://git.kernel.org/linus/645ca708f936b2fbeb79e52d7823e3eb2c0905f8
http://git.kernel.org/linus/30842f2989aacfaba3ccb39829b3417be9313dbe

Thanks, Eugene
-- 
Eugene Teo / Red Hat Security Response Team