[PATCH] cifs: fix strcat buffer overflow in smb21_set_oplock_level()

From: Christoph Probst
Date: Mon May 06 2019 - 11:26:21 EST

Change strcat to strcpy in the "None" case as it is never valid to append
"None" to any other message. It may also overflow char message[5], in a
race condition on cinode if cinode->oplock is unset by another thread
after "RHW" or "RH" had been written to message.

Signed-off-by: Christoph Probst <kernel@xxxxxxxxx>
fs/cifs/smb2ops.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/cifs/smb2ops.c b/fs/cifs/smb2ops.c
index c36ff0d..5fd5567 100644
--- a/fs/cifs/smb2ops.c
+++ b/fs/cifs/smb2ops.c
@@ -2936,7 +2936,7 @@ smb21_set_oplock_level(struct cifsInodeInfo *cinode, __u32 oplock,
strcat(message, "W");
if (!cinode->oplock)
- strcat(message, "None");
+ strcpy(message, "None");
cifs_dbg(FYI, "%s Lease granted on inode %p\n", message,