[PATCH v6.1 1/2] ksmbd: fix slab-out-of-bounds in smb_strndup_from_utf16()

[Vamsi Krishna Brahmajosyula]

From: Namjae Jeon <linkinjeon@xxxxxxxxxx>

[ Upstream commit a80a486d72e20bd12c335bcd38b6e6f19356b0aa ]

If ->NameOffset of smb2_create_req is smaller than Buffer offset of
smb2_create_req, slab-out-of-bounds read can happen from smb2_open.
This patch set the minimum value of the name offset to the buffer offset
to validate name length of smb2_create_req().

Cc: stable@xxxxxxxxxxxxxxx
Reported-by: Xuanzhe Yu <yuxuanzhe@xxxxxxxxxxx>
Signed-off-by: Namjae Jeon <linkinjeon@xxxxxxxxxx>
Signed-off-by: Steve French <stfrench@xxxxxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
Stable-dep-of: c6cd2e8d2d9a ("ksmbd: fix potencial out-of-bounds when buffer offset is invalid")
Signed-off-by: Vamsi Krishna Brahmajosyula <vamsi-krishna.brahmajosyula@xxxxxxxxxxxx>
---
 fs/smb/server/smb2misc.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/fs/smb/server/smb2misc.c b/fs/smb/server/smb2misc.c
index 03dded29a980..7c872ffb4b0a 100644
--- a/fs/smb/server/smb2misc.c
+++ b/fs/smb/server/smb2misc.c
@@ -107,7 +107,10 @@ static int smb2_get_data_area_len(unsigned int *off, unsigned int *len,
 	case SMB2_CREATE:
 	{
 		unsigned short int name_off =
-			le16_to_cpu(((struct smb2_create_req *)hdr)->NameOffset);
+			max_t(unsigned short int,
+			      le16_to_cpu(((struct smb2_create_req *)hdr)->NameOffset),
+			      offsetof(struct smb2_create_req, Buffer));
+
 		unsigned short int name_len =
 			le16_to_cpu(((struct smb2_create_req *)hdr)->NameLength);
 
-- 
2.39.4