linux-kernel - [PATCH AUTOSEL 5.10 88/88] cifs: prevent NULL deref in cifs_compose_mount

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Date:   Wed, 14 Jul 2021 15:43:03 -0400
From:   Sasha Levin <sashal@...nel.org>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:     Paulo Alcantara <pc@....nz>, Steve French <stfrench@...rosoft.com>,
        Sasha Levin <sashal@...nel.org>, linux-cifs@...r.kernel.org,
        samba-technical@...ts.samba.org
Subject: [PATCH AUTOSEL 5.10 88/88] 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 cc3ada12848d..42125601ebb1 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