]> git.proxmox.com Git - mirror_ubuntu-kernels.git/commit
o2dlm: fix NULL pointer dereference in o2dlm_blocking_ast_wrapper
authorSrinivas Eeda <srinivas.eeda@oracle.com>
Tue, 10 Feb 2015 22:09:26 +0000 (14:09 -0800)
committerLinus Torvalds <torvalds@linux-foundation.org>
Tue, 10 Feb 2015 22:30:30 +0000 (14:30 -0800)
commit99b8874e79619498ade354357f64299768642af6
tree60ab0830a9a41898749c001c047178f89fa952ac
parent10ab88117d069a552a5efdb4b5fb1c087a948c63
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>
fs/ocfs2/dlm/dlmast.c