3.6.11.9-rc1 stable review patch.
If anyone has any objections, please let me know.
------------------
From: David Jeffery <djeffery@xxxxxxxxxx>
[ Upstream commit 1c327d962fc420aea046c16215a552710bde8231 ]
In nlmsvc_retry_blocked, the check that the list is non-empty and acquiring
the pointer of the first entry is unprotected by any lock. This allows a rare
race condition when there is only one entry on the list. A function such as
nlmsvc_grant_callback() can be called, which will temporarily remove the entry
from the list. Between the list_empty() and list_entry(),the list may become
empty, causing an invalid pointer to be used as an nlm_block, leading to a
possible crash.
This patch adds the nlm_block_lock around these calls to prevent concurrent
use of the nlm_blocked list.
This was a regression introduced by
f904be9cc77f361d37d71468b13ff3d1a1823dea "lockd: Mostly remove BKL from
the server".
Cc: Bryan Schumaker <bjschuma@xxxxxxxxxx>
Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: David Jeffery <djeffery@xxxxxxxxxx>
Signed-off-by: J. Bruce Fields <bfields@xxxxxxxxxx>
Signed-off-by: Steven Rostedt <rostedt@xxxxxxxxxxx>
---
fs/lockd/svclock.c | 4 ++++
1 file changed, 4 insertions(+)
diff --git a/fs/lockd/svclock.c b/fs/lockd/svclock.c
index 8d80c99..57a3922 100644
--- a/fs/lockd/svclock.c
+++ b/fs/lockd/svclock.c
@@ -939,6 +939,7 @@ nlmsvc_retry_blocked(void)
unsigned long timeout = MAX_SCHEDULE_TIMEOUT;
struct nlm_block *block;
+ spin_lock(&nlm_blocked_lock);
while (!list_empty(&nlm_blocked) && !kthread_should_stop()) {
block = list_entry(nlm_blocked.next, struct nlm_block, b_list);
@@ -948,6 +949,7 @@ nlmsvc_retry_blocked(void)
timeout = block->b_when - jiffies;
break;
}
+ spin_unlock(&nlm_blocked_lock);
dprintk("nlmsvc_retry_blocked(%p, when=%ld)\n",
block, block->b_when);
@@ -957,7 +959,9 @@ nlmsvc_retry_blocked(void)
retry_deferred_block(block);
} else
nlmsvc_grant_blocked(block);
+ spin_lock(&nlm_blocked_lock);
}
+ spin_unlock(&nlm_blocked_lock);
return timeout;
}
--
1.7.10.4
--
To unsubscribe from this list: send the line "unsubscribe stable" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html