The validate_negotiate_info_req struct definition includes an extra
field to access the data coming after the header. This causes the check
in fsctl_validate_negotiate_info() to count the first element of the
array twice. This in turn makes some valid requests fail, depending on
whether they include padding or not.
Fixes: f7db8fd03a4b ("ksmbd: add validation in smb2_ioctl")
Signed-off-by: Marios Makassikis <mmakassikis@xxxxxxxxxx>
---
This causes mounts to fail on older kernels (v4.19 on debian10) when
specifying vers=3.0.
fs/ksmbd/smb2pdu.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/fs/ksmbd/smb2pdu.c b/fs/ksmbd/smb2pdu.c
index 7e448df3f847..a03b53df3f04 100644
--- a/fs/ksmbd/smb2pdu.c
+++ b/fs/ksmbd/smb2pdu.c
@@ -7312,7 +7312,7 @@ static int fsctl_validate_negotiate_info(struct ksmbd_conn *conn,
int ret = 0;
int dialect;
- if (in_buf_len < sizeof(struct validate_negotiate_info_req) +
+ if (in_buf_len < offsetof(struct validate_negotiate_info_req, Dialects) +
le16_to_cpu(neg_req->DialectCount) * sizeof(__le16))
return -EINVAL;
--
2.25.1
