cifs: Fix potential OOB access of lock element array

commit b9a74cde94957d82003fb9f7ab4777938ca851cd upstream.

If maxBuf is small but non-zero, it could result in a zero sized lock
element array which we would then try and access OOB.

Signed-off-by: Ross Lagerwall <ross.lagerwall@citrix.com>
Signed-off-by: Steve French <stfrench@microsoft.com>
CC: Stable <stable@vger.kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/fs/cifs/file.c b/fs/cifs/file.c
index 8d41ca7..7b637fc 100644 (file)
--- a/fs/cifs/file.c
+++ b/fs/cifs/file.c
@@ -1120,10 +1120,10 @@ cifs_push_mandatory_locks(struct cifsFileInfo *cfile)
 
        /*
         * Accessing maxBuf is racy with cifs_reconnect - need to store value
-        * and check it for zero before using.
+        * and check it before using.
         */
        max_buf = tcon->ses->server->maxBuf;
-       if (!max_buf) {
+       if (max_buf < (sizeof(struct smb_hdr) + sizeof(LOCKING_ANDX_RANGE))) {
                free_xid(xid);
                return -EINVAL;
        }
@@ -1460,10 +1460,10 @@ cifs_unlock_range(struct cifsFileInfo *cfile, struct file_lock *flock,
 
        /*
         * Accessing maxBuf is racy with cifs_reconnect - need to store value
-        * and check it for zero before using.
+        * and check it before using.
         */
        max_buf = tcon->ses->server->maxBuf;
-       if (!max_buf)
+       if (max_buf < (sizeof(struct smb_hdr) + sizeof(LOCKING_ANDX_RANGE)))
                return -EINVAL;
 
        max_num = (max_buf - sizeof(struct smb_hdr)) /

diff --git a/fs/cifs/smb2file.c b/fs/cifs/smb2file.c
index 4ed10dd..2fc3d31 100644 (file)
--- a/fs/cifs/smb2file.c
+++ b/fs/cifs/smb2file.c
@@ -122,10 +122,10 @@ smb2_unlock_range(struct cifsFileInfo *cfile, struct file_lock *flock,
 
        /*
         * Accessing maxBuf is racy with cifs_reconnect - need to store value
-        * and check it for zero before using.
+        * and check it before using.
         */
        max_buf = tcon->ses->server->maxBuf;
-       if (!max_buf)
+       if (max_buf < sizeof(struct smb2_lock_element))
                return -EINVAL;
 
        max_num = max_buf / sizeof(struct smb2_lock_element);