releases/6.16.8/smb-client-fix-compound-alignment-with-encryption.patch

From 90f7c100d2dd99d5cd5be950d553edd2647e6cc8 Mon Sep 17 00:00:00 2001
From: Paulo Alcantara <pc@manguebit.org>
Date: Sat, 6 Sep 2025 21:19:29 -0300
Subject: smb: client: fix compound alignment with encryption

From: Paulo Alcantara <pc@manguebit.org>

commit 90f7c100d2dd99d5cd5be950d553edd2647e6cc8 upstream.

The encryption layer can't handle the padding iovs, so flatten the
compound request into a single buffer with required padding to prevent
the server from dropping the connection when finding unaligned
compound requests.

Fixes: bc925c1216f0 ("smb: client: improve compound padding in encryption")
Signed-off-by: Paulo Alcantara (Red Hat) <pc@manguebit.org>
Reviewed-by: David Howells <dhowells@redhat.com>
Cc: linux-cifs@vger.kernel.org
Cc: stable@vger.kernel.org
Signed-off-by: Steve French <stfrench@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 fs/smb/client/smb2ops.c |   28 +++++++++++++++++++++++++---
 1 file changed, 25 insertions(+), 3 deletions(-)

--- a/fs/smb/client/smb2ops.c
+++ b/fs/smb/client/smb2ops.c
@@ -2640,13 +2640,35 @@ smb2_set_next_command(struct cifs_tcon *
 	}
 
 	/* SMB headers in a compound are 8 byte aligned. */
-	if (!IS_ALIGNED(len, 8)) {
-		num_padding = 8 - (len & 7);
+	if (IS_ALIGNED(len, 8))
+		goto out;
+
+	num_padding = 8 - (len & 7);
+	if (smb3_encryption_required(tcon)) {
+		int i;
+
+		/*
+		 * Flatten request into a single buffer with required padding as
+		 * the encryption layer can't handle the padding iovs.
+		 */
+		for (i = 1; i < rqst->rq_nvec; i++) {
+			memcpy(rqst->rq_iov[0].iov_base +
+			       rqst->rq_iov[0].iov_len,
+			       rqst->rq_iov[i].iov_base,
+			       rqst->rq_iov[i].iov_len);
+			rqst->rq_iov[0].iov_len += rqst->rq_iov[i].iov_len;
+		}
+		memset(rqst->rq_iov[0].iov_base + rqst->rq_iov[0].iov_len,
+		       0, num_padding);
+		rqst->rq_iov[0].iov_len += num_padding;
+		rqst->rq_nvec = 1;
+	} else {
 		rqst->rq_iov[rqst->rq_nvec].iov_base = smb2_padding;
 		rqst->rq_iov[rqst->rq_nvec].iov_len = num_padding;
 		rqst->rq_nvec++;
-		len += num_padding;
 	}
+	len += num_padding;
+out:
 	shdr->NextCommand = cpu_to_le32(len);
 }