ksmbd: align aux_payload_buf to avoid OOB reads in cryptographic operations

The aux_payload_buf allocation in SMB2 read is performed without ensuring
alignment, which could result in out-of-bounds (OOB) reads during
cryptographic operations such as crypto_xor or ghash. This patch aligns
the allocation of aux_payload_buf to prevent these issues.
(Note that to add this patch to stable would require modifications due
to recent patch "ksmbd: use __GFP_RETRY_MAYFAIL")

Signed-off-by: Norbert Szetei <norbert@doyensec.com>
Acked-by: Namjae Jeon <linkinjeon@kernel.org>
Signed-off-by: Steve French <stfrench@microsoft.com>

Author: nszetei

fs/smb/server/smb2pdu.c

@@ -6680,7 +6680,7 @@ int smb2_read(struct ksmbd_work *work)
 	ksmbd_debug(SMB, "filename %pD, offset %lld, len %zu\n",
 		    fp->filp, offset, length);
 
-	aux_payload_buf = kvzalloc(length, KSMBD_DEFAULT_GFP);
+	aux_payload_buf = kvzalloc(ALIGN(length, 8), KSMBD_DEFAULT_GFP);
 	if (!aux_payload_buf) {
 		err = -ENOMEM;
 		goto out;