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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
parent10ab88117d069a552a5efdb4b5fb1c087a948c63 (diff)
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>
-rw-r--r--fs/ocfs2/dlm/dlmast.c6
1 files changed, 5 insertions, 1 deletions
diff --git a/fs/ocfs2/dlm/dlmast.c b/fs/ocfs2/dlm/dlmast.c
index b46278f9ae44..fd6bbbbd7d78 100644
--- a/fs/ocfs2/dlm/dlmast.c
+++ b/fs/ocfs2/dlm/dlmast.c
@@ -385,8 +385,12 @@ int dlm_proxy_ast_handler(struct o2net_msg *msg, u32 len, void *data,
head = &res->granted;
list_for_each_entry(lock, head, list) {
- if (lock->ml.cookie == cookie)
+ /* if lock is found but unlock is pending ignore the bast */
+ if (lock->ml.cookie == cookie) {
+ if (lock->unlock_pending)
+ break;
goto do_ast;
+ }
}
mlog(0, "Got %sast for unknown lock! cookie=%u:%llu, name=%.*s, "