linux-kernel - [PATCH 5.13 100/156] cifs: prevent NULL deref in cifs_compose_mount

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Date:   Thu, 22 Jul 2021 18:31:15 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, "Paulo Alcantara (SUSE)" <pc@....nz>,
        Steve French <stfrench@...rosoft.com>,
        Sasha Levin <sashal@...nel.org>
Subject: [PATCH 5.13 100/156] cifs: prevent NULL deref in cifs_compose_mount_options()

From: Paulo Alcantara <pc@....nz>

[ Upstream commit 03313d1c3a2f086bb60920607ab79ac8f8578306 ]

The optional @ref parameter might contain an NULL node_name, so
prevent dereferencing it in cifs_compose_mount_options().

Addresses-Coverity: 1476408 ("Explicit null dereferenced")
Signed-off-by: Paulo Alcantara (SUSE) <pc@....nz>
Signed-off-by: Steve French <stfrench@...rosoft.com>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 fs/cifs/cifs_dfs_ref.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/fs/cifs/cifs_dfs_ref.c b/fs/cifs/cifs_dfs_ref.c
index 8dec4edc8a9f..35a6007d88a9 100644
--- a/fs/cifs/cifs_dfs_ref.c
+++ b/fs/cifs/cifs_dfs_ref.c
@@ -151,6 +151,9 @@ char *cifs_compose_mount_options(const char *sb_mountdata,
 		return ERR_PTR(-EINVAL);
 
 	if (ref) {
+		if (WARN_ON_ONCE(!ref->node_name || ref->path_consumed < 0))
+			return ERR_PTR(-EINVAL);
+
 		if (strlen(fullpath) - ref->path_consumed) {
 			prepath = fullpath + ref->path_consumed;
 			/* skip initial delimiter */
-- 
2.30.2