linux-kernel - [PATCH] cifs: fix strcat buffer overflow in smb21_set_oplock

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Message-Id: <1557155792-2703-1-git-send-email-kernel@probst.it>
Date:   Mon,  6 May 2019 17:16:32 +0200
From:   Christoph Probst <kernel@...bst.it>
To:     linux-cifs@...r.kernel.org
Cc:     Steve French <sfrench@...ba.org>, samba-technical@...ts.samba.org,
        linux-kernel@...r.kernel.org, Christoph Probst <kernel@...bst.it>
Subject: [PATCH] cifs: fix strcat buffer overflow in smb21_set_oplock_level()

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@...bst.it>
---
 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,
 		 &cinode->vfs_inode);
 }
-- 
2.1.4