linux-kernel - [PATCH 1/2] media: uvcvideo: Avoid invalid memory access

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Date:   Tue, 30 Nov 2021 15:50:25 +0000
From:   Ricardo Ribalda <ribalda@...omium.org>
To:     Laurent Pinchart <laurent.pinchart@...asonboard.com>,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        Hans Verkuil <hverkuil-cisco@...all.nl>,
        linux-media@...r.kernel.org, linux-kernel@...r.kernel.org
Cc:     Ricardo Ribalda <ribalda@...omium.org>
Subject: [PATCH 1/2] media: uvcvideo: Avoid invalid memory access

If mappings points to an invalid memory, we will be invalid accessing
it.
Solve it by initializing the value of the variable mapping and by
changing the order in the conditional statement (to avoid accessing
mapping->id if not needed).

Fix:
kasan: GPF could be caused by NULL-ptr deref or user memory access
general protection fault: 0000 [#1] PREEMPT SMP KASAN NOPTI

Fixes: 6350d6a4ed487 ("media: uvcvideo: Set error_idx during ctrl_commit errors")
Signed-off-by: Ricardo Ribalda <ribalda@...omium.org>
---
 drivers/media/usb/uvc/uvc_ctrl.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/drivers/media/usb/uvc/uvc_ctrl.c b/drivers/media/usb/uvc/uvc_ctrl.c
index 30bfe9069a1fb..f7b7add3cfa59 100644
--- a/drivers/media/usb/uvc/uvc_ctrl.c
+++ b/drivers/media/usb/uvc/uvc_ctrl.c
@@ -852,8 +852,8 @@ static void __uvc_find_control(struct uvc_entity *entity, u32 v4l2_id,
 				return;
 			}
 
-			if ((*mapping == NULL || (*mapping)->id > map->id) &&
-			    (map->id > v4l2_id) && next) {
+			if (next && (map->id > v4l2_id) &&
+			    (*mapping == NULL || (*mapping)->id > map->id)) {
 				*control = ctrl;
 				*mapping = map;
 			}
@@ -1638,7 +1638,7 @@ static int uvc_ctrl_find_ctrl_idx(struct uvc_entity *entity,
 				  struct v4l2_ext_controls *ctrls,
 				  struct uvc_control *uvc_control)
 {
-	struct uvc_control_mapping *mapping;
+	struct uvc_control_mapping *mapping = NULL;
 	struct uvc_control *ctrl_found;
 	unsigned int i;
 
-- 
2.34.0.384.gca35af8252-goog