FAILED: patch "[PATCH] ksmbd: avoid out of bounds access in decode_preauth_ctxt()" failed to apply to 5.15-stable tree

[<gregkh@xxxxxxxxxxxxxxxxxxx>]

The patch below does not apply to the 5.15-stable tree.
If someone wants it applied there, or to any other stable or longterm
tree, then please email the backport, including the original git commit
id to <stable@xxxxxxxxxxxxxxx>.

To reproduce the conflict and resubmit, you may use the following commands:

git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-5.15.y
git checkout FETCH_HEAD
git cherry-pick -x e7067a446264a7514fa1cfaa4052cdb6803bc6a2
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<stable@xxxxxxxxxxxxxxx>' --in-reply-to '2023041754-retread-approach-96af@gregkh' --subject-prefix 'PATCH 5.15.y' HEAD^..

Possible dependencies:

e7067a446264 ("ksmbd: avoid out of bounds access in decode_preauth_ctxt()")

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

>From e7067a446264a7514fa1cfaa4052cdb6803bc6a2 Mon Sep 17 00:00:00 2001
From: David Disseldorp <ddiss@xxxxxxx>
Date: Thu, 13 Apr 2023 23:49:57 +0900
Subject: [PATCH] ksmbd: avoid out of bounds access in decode_preauth_ctxt()

Confirm that the accessed pneg_ctxt->HashAlgorithms address sits within
the SMB request boundary; deassemble_neg_contexts() only checks that the
eight byte smb2_neg_context header + (client controlled) DataLength are
within the packet boundary, which is insufficient.

Checking for sizeof(struct smb2_preauth_neg_context) is overkill given
that the type currently assumes SMB311_SALT_SIZE bytes of trailing Salt.

Signed-off-by: David Disseldorp <ddiss@xxxxxxx>
Acked-by: Namjae Jeon <linkinjeon@xxxxxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx>
Signed-off-by: Steve French <stfrench@xxxxxxxxxxxxx>

diff --git a/fs/ksmbd/smb2pdu.c b/fs/ksmbd/smb2pdu.c
index 8af939a181be..67b7e766a06b 100644
--- a/fs/ksmbd/smb2pdu.c
+++ b/fs/ksmbd/smb2pdu.c
@@ -876,17 +876,21 @@ static void assemble_neg_contexts(struct ksmbd_conn *conn,
 }
 
 static __le32 decode_preauth_ctxt(struct ksmbd_conn *conn,
-				  struct smb2_preauth_neg_context *pneg_ctxt)
+				  struct smb2_preauth_neg_context *pneg_ctxt,
+				  int len_of_ctxts)
 {
-	__le32 err = STATUS_NO_PREAUTH_INTEGRITY_HASH_OVERLAP;
+	/*
+	 * sizeof(smb2_preauth_neg_context) assumes SMB311_SALT_SIZE Salt,
+	 * which may not be present. Only check for used HashAlgorithms[1].
+	 */
+	if (len_of_ctxts < MIN_PREAUTH_CTXT_DATA_LEN)
+		return STATUS_INVALID_PARAMETER;
 
-	if (pneg_ctxt->HashAlgorithms == SMB2_PREAUTH_INTEGRITY_SHA512) {
-		conn->preauth_info->Preauth_HashId =
-			SMB2_PREAUTH_INTEGRITY_SHA512;
-		err = STATUS_SUCCESS;
-	}
+	if (pneg_ctxt->HashAlgorithms != SMB2_PREAUTH_INTEGRITY_SHA512)
+		return STATUS_NO_PREAUTH_INTEGRITY_HASH_OVERLAP;
 
-	return err;
+	conn->preauth_info->Preauth_HashId = SMB2_PREAUTH_INTEGRITY_SHA512;
+	return STATUS_SUCCESS;
 }
 
 static void decode_encrypt_ctxt(struct ksmbd_conn *conn,
@@ -1014,7 +1018,8 @@ static __le32 deassemble_neg_contexts(struct ksmbd_conn *conn,
 				break;
 
 			status = decode_preauth_ctxt(conn,
-						     (struct smb2_preauth_neg_context *)pctx);
+						     (struct smb2_preauth_neg_context *)pctx,
+						     len_of_ctxts);
 			if (status != STATUS_SUCCESS)
 				break;
 		} else if (pctx->ContextType == SMB2_ENCRYPTION_CAPABILITIES) {