[PATCH 5.10 073/120] smb3: Fix out-of-bounds bug in SMB2_negotiate()

Greg Kroah-Hartman
2021-02-08T17:17:40Z

From: Gustavo A. R. Silva <gustavoars@kernel.org>

commit 8d8d1dbefc423d42d626cf5b81aac214870ebaab upstream.

While addressing some warnings generated by -Warray-bounds, I found this
bug that was introduced back in 2017:

CC [M] fs/cifs/smb2pdu.o
fs/cifs/smb2pdu.c: In function ‘SMB2_negotiate’:
fs/cifs/smb2pdu.c:822:16: warning: array subscript 1 is above array bounds
of ‘__le16[1]’ {aka ‘short unsigned int[1]’} [-Warray-bounds]
822 | req->Dialects[1] = cpu_to_le16(SMB30_PROT_ID);
| ~~~~~~~~~~~~~^~~
fs/cifs/smb2pdu.c:823:16: warning: array subscript 2 is above array bounds
of ‘__le16[1]’ {aka ‘short unsigned int[1]’} [-Warray-bounds]
823 | req->Dialects[2] = cpu_to_le16(SMB302_PROT_ID);
| ~~~~~~~~~~~~~^~~
fs/cifs/smb2pdu.c:824:16: warning: array subscript 3 is above array bounds
of ‘__le16[1]’ {aka ‘short unsigned int[1]’} [-Warray-bounds]
824 | req->Dialects[3] = cpu_to_le16(SMB311_PROT_ID);
| ~~~~~~~~~~~~~^~~
fs/cifs/smb2pdu.c:816:16: warning: array subscript 1 is above array bounds
of ‘__le16[1]’ {aka ‘short unsigned int[1]’} [-Warray-bounds]
816 | req->Dialects[1] = cpu_to_le16(SMB302_PROT_ID);
| ~~~~~~~~~~~~~^~~

At the time, the size of array _Dialects_ was changed from 1 to 3 in struct
validate_negotiate_info_req, and then in 2019 it was changed from 3 to 4,
but those changes were never made in struct smb2_negotiate_req, which has
led to a 3 and a half years old out-of-bounds bug in function
SMB2_negotiate() (fs/cifs/smb2pdu.c).

Fix this by increasing the size of array _Dialects_ in struct
smb2_negotiate_req to 4.

Fixes: 9764c02fcbad ("SMB3: Add support for multidialect negotiate (SMB2.1 and later)")
Fixes: d5c7076b772a ("smb3: add smb3.1.1 to default dialect list")
Cc: stable@vger.kernel.org
Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org>
Signed-off-by: Steve French <stfrench@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
fs/cifs/smb2pdu.h | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

--- a/fs/cifs/smb2pdu.h
+++ b/fs/cifs/smb2pdu.h
@@ -286,7 +286,7 @@ struct smb2_negotiate_req {
__le32 NegotiateContextOffset; /* SMB3.1.1 only. MBZ earlier */
__le16 NegotiateContextCount; /* SMB3.1.1 only. MBZ earlier */
__le16 Reserved2;
- __le16 Dialects[1]; /* One dialect (vers=) at a time for now */
+ __le16 Dialects[4]; /* BB expand this if autonegotiate > 4 dialects */
} __packed;

/* Dialects */