[PATCH 6.6.y 2/2] ksmbd: zero pipe read compound padding

[Sasha Levin <sashal@kernel.org>]

From: Namjae Jeon <linkinjeon@kernel.org>

[ Upstream commit 73f860489e3be2245598d1819226304fc5b87291 ]

Compound response handling extends the last response iov to an eight-byte
boundary.

smb2_read_pipe() allocates only the payload size, so the alignment padding
can expose up to seven bytes of uninitialized kernel heap memory.

Allocate the aligned size and clear the unused tail before pinning the
response buffer.

Fixes: e2b76ab8b5c9 ("ksmbd: add support for read compound")
Reported-by: Cheryl Babcock <cheryl@renat.io>
Signed-off-by: Namjae Jeon <linkinjeon@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 fs/smb/server/smb2pdu.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/fs/smb/server/smb2pdu.c b/fs/smb/server/smb2pdu.c
index 93185ea112014..e7659290c3200 100644
--- a/fs/smb/server/smb2pdu.c
+++ b/fs/smb/server/smb2pdu.c
@@ -6717,13 +6717,18 @@ static noinline int smb2_read_pipe(struct ksmbd_work *work)
 		}
 
 		aux_payload_buf =
-			kvmalloc(rpc_resp->payload_sz, KSMBD_DEFAULT_GFP);
+			kvmalloc(ALIGN(rpc_resp->payload_sz, 8),
+				 KSMBD_DEFAULT_GFP);
 		if (!aux_payload_buf) {
 			err = -ENOMEM;
 			goto out;
 		}
 
 		memcpy(aux_payload_buf, rpc_resp->payload, rpc_resp->payload_sz);
+		if (rpc_resp->payload_sz & 7)
+			memset(aux_payload_buf + rpc_resp->payload_sz, 0,
+			       ALIGN(rpc_resp->payload_sz, 8) -
+			       rpc_resp->payload_sz);
 
 		nbytes = rpc_resp->payload_sz;
 		err = ksmbd_iov_pin_rsp_read(work, (void *)rsp,
-- 
2.53.0