[PATCH 6.12.y] ksmbd: do not read past the DACL in the access denied debug message

[Sasha Levin <sashal@kernel.org>]

From: Ian Bridges <icb@fastmail.org>

[ Upstream commit 8296a64df5448548f410fb246c1d88a93609602b ]

When smb_check_perm_dacl() falls back to the POSIX ACL and then denies
the request, its debug message prints the access mask of the ACE that
the second DACL walk stopped at. On that path the walk ran to the end
of the DACL, so the pointer is one past the last ACE. If the DACL is
the last part of the stored security descriptor, the message reads 4
bytes past the buffer, and KASAN reports a slab-out-of-bounds read in
smb_check_perm_dacl().

Print the requested and allowed masks instead. They are what the check
compares.

Fixes: e2f34481b24d ("cifsd: add server-side procedures for SMB3")
Cc: stable@vger.kernel.org
Signed-off-by: Ian Bridges <icb@fastmail.org>
Signed-off-by: Namjae Jeon <linkinjeon@kernel.org>
[ sashal: adjusted context for the check_access_bits label and expanded access mask ]
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 fs/smb/server/smbacl.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/fs/smb/server/smbacl.c b/fs/smb/server/smbacl.c
index 63f7bccb4d9af..d8c01e775d941 100644
--- a/fs/smb/server/smbacl.c
+++ b/fs/smb/server/smbacl.c
@@ -1650,8 +1650,8 @@ int smb_check_perm_dacl(struct ksmbd_conn *conn, const struct path *path,
 check_access_bits:
 	if (granted &
 	    ~(access_bits | FILE_READ_ATTRIBUTES | READ_CONTROL | WRITE_DAC | DELETE)) {
-		ksmbd_debug(SMB, "Access denied with winACL, granted : %x, access_req : %x\n",
-			    granted, le32_to_cpu(ace->access_req));
+		ksmbd_debug(SMB, "Access denied with winACL, requested : %x, allowed : %x\n",
+			    granted, access_bits);
 		rc = -EACCES;
 		goto err_out;
 	}
-- 
2.53.0