On Wed, Feb 04, 2015 at 04:00:49PM -0800, Andrew Morton wrote:
> From: Srinivas Eeda <srinivas.e...@oracle.com>
> Subject: 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: [<ffffffffa015e023>] o2dlm_blocking_ast_wrapper+0xd/0x16
> [<ffffffffa034e3db>] dlm_do_local_bast+0x8e/0x97 [ocfs2_dlm]
> [<ffffffffa034f366>] dlm_proxy_ast_handler+0x838/0x87e [ocfs2_dlm]
> [<ffffffffa0308abe>] o2net_process_message+0x395/0x5b8 [ocfs2_nodemanager]
> [<ffffffffa030aac8>] o2net_rx_until_empty+0x762/0x90d [ocfs2_nodemanager]
> [<ffffffff81071802>] worker_thread+0x14d/0x1ed
>
> [a...@linux-foundation.org: coding-style fixes]
> Signed-off-by: Srinivas Eeda <srinivas.e...@oracle.com>
Reviewed-by: Mark Fasheh <mfas...@suse.de>
--Mark
--
Mark Fasheh
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