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authorSrinivas Eeda <srinivas.eeda@oracle.com>2015-02-10 14:09:26 -0800
committerLinus Torvalds <torvalds@linux-foundation.org>2015-02-10 14:30:30 -0800
commit99b8874e79619498ade354357f64299768642af6 (patch)
tree60ab0830a9a41898749c001c047178f89fa952ac /fs/ioctl.c
parent10ab88117d069a552a5efdb4b5fb1c087a948c63 (diff)
downloadlinux-99b8874e79619498ade354357f64299768642af6.tar.bz2
o2dlm: fix NULL pointer dereference in o2dlm_blocking_ast_wrapper
A tiny race between BAST and unlock message causes the NULL dereference. A node sends an unlock request to master and receives a response. Before processing the response it receives a BAST from the master. Since both requests are processed by different threads it creates a race. While the BAST is being processed, lock can get freed by unlock code. This patch makes bast to return immediately if lock is found but unlock is pending. The code should handle this race. We also have to fix master node to skip sending BAST after receiving unlock message. Below is the crash stack BUG: unable to handle kernel NULL pointer dereference at 0000000000000048 IP: o2dlm_blocking_ast_wrapper+0xd/0x16 dlm_do_local_bast+0x8e/0x97 [ocfs2_dlm] dlm_proxy_ast_handler+0x838/0x87e [ocfs2_dlm] o2net_process_message+0x395/0x5b8 [ocfs2_nodemanager] o2net_rx_until_empty+0x762/0x90d [ocfs2_nodemanager] worker_thread+0x14d/0x1ed [akpm@linux-foundation.org: coding-style fixes] Signed-off-by: Srinivas Eeda <srinivas.eeda@oracle.com> Reviewed-by: Mark Fasheh <mfasheh@suse.de> Cc: Joel Becker <jlbec@evilplan.org> Cc: Joseph Qi <joseph.qi@huawei.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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