cifs: Fix use-after-free on mid_q_entry
With CIFS_DEBUG_2 enabled, additional debug information is tracked inside each
mid_q_entry struct, however cifs_save_when_sent may use the mid_q_entry after it
has been freed from the appropriate callback if the transport layer has very low
latency. Holding the srv_mutex fixes this use-after-free, as cifs_save_when_sent
is called while the srv_mutex is held while the request is sent.
Signed-off-by: Christopher Oo <t-chriso@microsoft.com>
diff --git a/fs/cifs/transport.c b/fs/cifs/transport.c
index 126f46b..2a24c52 100644
--- a/fs/cifs/transport.c
+++ b/fs/cifs/transport.c
@@ -644,7 +644,9 @@
}
spin_unlock(&GlobalMid_Lock);
+ mutex_lock(&server->srv_mutex);
DeleteMidQEntry(mid);
+ mutex_unlock(&server->srv_mutex);
return rc;
}