[Ocfs2-devel] [patch 2/4] o2dlm: fix NULL pointer dereference in o2dlm_blocking_ast_wrapper

[Mark Fasheh]

On Wed, Feb 04, 2015 at 04:00:49PM -0800, Andrew Morton wrote:
> From: Srinivas Eeda <srinivas.eeda at 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
> 
> [akpm at linux-foundation.org: coding-style fixes]
> Signed-off-by: Srinivas Eeda <srinivas.eeda at oracle.com>

Reviewed-by: Mark Fasheh <mfasheh at suse.de>
	--Mark

--
Mark Fasheh