[PATCH v2 6/7] ksmbd: fix invalid request buffer access in compound

Namjae Jeon
2021-09-25T13:17:25Z

Ronnie reported invalid request buffer access in chained command when
inserting garbage value to NextCommand of compound request.
This patch add validation check to avoid this issue.

Cc: Tom Talpey <tom@talpey.com>
Cc: Ronnie Sahlberg <ronniesahlberg@gmail.com>
Cc: Ralph Böhme <slow@samba.org>
Cc: Steve French <smfrench@gmail.com>
Cc: Sergey Senozhatsky <senozhatsky@chromium.org>
Acked-by: Hyunchul Lee <hyc.lee@gmail.com>
Signed-off-by: Namjae Jeon <linkinjeon@kernel.org>
---
fs/ksmbd/smb2pdu.c | 13 +++++++++++--
1 file changed, 11 insertions(+), 2 deletions(-)

diff --git a/fs/ksmbd/smb2pdu.c b/fs/ksmbd/smb2pdu.c
index c463375b0a4a..713f861fdaad 100644
--- a/fs/ksmbd/smb2pdu.c
+++ b/fs/ksmbd/smb2pdu.c
@@ -459,13 +459,22 @@ static void init_chained_smb2_rsp(struct ksmbd_work *work)
bool is_chained_smb2_message(struct ksmbd_work *work)
{
struct smb2_hdr *hdr = work->request_buf;
- unsigned int len;
+ unsigned int len, next_cmd;

if (hdr->ProtocolId != SMB2_PROTO_NUMBER)
return false;

hdr = ksmbd_req_buf_next(work);
- if (le32_to_cpu(hdr->NextCommand) > 0) {
+ next_cmd = le32_to_cpu(hdr->NextCommand);
+ if (next_cmd > 0) {
+ if ((u64)work->next_smb2_rcv_hdr_off + next_cmd +
+ __SMB2_HEADER_STRUCTURE_SIZE >
+ get_rfc1002_len(work->request_buf)) {
+ pr_err("next command(%u) offset exceeds smb msg size\n",
+ next_cmd);
+ return false;
+ }
+
ksmbd_debug(SMB, "got SMB2 chained command\n");
init_chained_smb2_rsp(work);
return true;
--
2.25.1