linux-kernel - [PATCH] um: ubd: Fix crash from option parsing

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Date:   Tue, 19 Jan 2021 18:19:45 +0000
From:   Paul Lawrence <paullawrence@...gle.com>
To:     Jeff Dike <jdike@...toit.com>, Richard Weinberger <richard@....at>,
        Anton Ivanov <anton.ivanov@...bridgegreys.com>,
        Gabriel Krisman Bertazi <krisman@...labora.com>,
        Christopher Obbard <chris.obbard@...labora.com>,
        Paul Lawrence <paullawrence@...gle.com>
Cc:     linux-um@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: [PATCH] um: ubd: Fix crash from option parsing

Below patch will cause NULL ptr dereferences if the optional filenames
are not present.

Fixes: ef3ba87cb7c9 (um: ubd: Set device serial attribute from cmdline)
Signed-off-by: Paul Lawrence <paullawrence@...gle.com>
---
 arch/um/drivers/ubd_kern.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/arch/um/drivers/ubd_kern.c b/arch/um/drivers/ubd_kern.c
index 13b1fe694b90..704989088f28 100644
--- a/arch/um/drivers/ubd_kern.c
+++ b/arch/um/drivers/ubd_kern.c
@@ -371,15 +371,15 @@ static int ubd_setup_common(char *str, int *index_out, char **error_out)
 
 break_loop:
 	file = strsep(&str, ",:");
-	if (*file == '\0')
+	if (file && *file == '\0')
 		file = NULL;
 
 	backing_file = strsep(&str, ",:");
-	if (*backing_file == '\0')
+	if (backing_file && *backing_file == '\0')
 		backing_file = NULL;
 
 	serial = strsep(&str, ",:");
-	if (*serial == '\0')
+	if (serial && *serial == '\0')
 		serial = NULL;
 
 	if (backing_file && ubd_dev->no_cow) {
-- 
2.30.0.284.gd98b1dd5eaa7-goog