linux-kernel - [PATCH 5.15 4/5] ksmbd: fix SMB 3.11 posix extension mount failure

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Date:   Wed,  9 Feb 2022 20:14:29 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Steve French <smfrench@...il.com>,
        Steve French <stfrench@...rosoft.com>,
        Namjae Jeon <linkinjeon@...nel.org>
Subject: [PATCH 5.15 4/5] ksmbd: fix SMB 3.11 posix extension mount failure

From: Namjae Jeon <linkinjeon@...nel.org>

commit 9ca8581e79e51c57e60b3b8e3b89d816448f49fe upstream.

cifs client set 4 to DataLength of create_posix context, which mean
Mode variable of create_posix context is only available. So buffer
validation of ksmbd should check only the size of Mode except for
the size of Reserved variable.

Fixes: 8f77150c15f8 ("ksmbd: add buffer validation for SMB2_CREATE_CONTEXT")
Cc: stable@...r.kernel.org # v5.15+
Reported-by: Steve French <smfrench@...il.com>
Tested-by: Steve French <stfrench@...rosoft.com>
Signed-off-by: Namjae Jeon <linkinjeon@...nel.org>
Signed-off-by: Steve French <stfrench@...rosoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 fs/ksmbd/smb2pdu.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/fs/ksmbd/smb2pdu.c
+++ b/fs/ksmbd/smb2pdu.c
@@ -2690,7 +2690,7 @@ int smb2_open(struct ksmbd_work *work)
 					(struct create_posix *)context;
 				if (le16_to_cpu(context->DataOffset) +
 				    le32_to_cpu(context->DataLength) <
-				    sizeof(struct create_posix)) {
+				    sizeof(struct create_posix) - 4) {
 					rc = -EINVAL;
 					goto err_out1;
 				}