linux-kernel - [PATCH] media: ti-vpe: cal: Fix a NULL pointer dereference in cal_ctx_v4l2_init

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Message-Id: <20220124172001.62457-1-zhou1615@umn.edu>
Date:   Tue, 25 Jan 2022 01:20:01 +0800
From:   Zhou Qingyang <zhou1615@....edu>
To:     zhou1615@....edu
Cc:     kjlu@....edu, Benoit Parrot <bparrot@...com>,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        Hans Verkuil <hverkuil-cisco@...all.nl>,
        Laurent Pinchart <laurent.pinchart@...asonboard.com>,
        linux-media@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH] media: ti-vpe: cal: Fix a NULL pointer dereference in cal_ctx_v4l2_init_formats()

In cal_ctx_v4l2_init_formats(), devm_kzalloc() is assigned to fw and there
is a dereference of it after that, which could lead to NULL pointer
dereference on failure of devm_kzalloc().

Fix this bug by adding a NULL check of ctx->active_fmt.

This bug was found by a static analyzer.

Builds with 'make allyesconfig' show no new warnings,
and our static analyzer no longer warns about this code.

Fixes: 7168155002cf ("media: ti-vpe: cal: Move format handling to cal.c and expose helpers")
Signed-off-by: Zhou Qingyang <zhou1615@....edu>
--
The analysis employs differential checking to identify inconsistent 
security operations (e.g., checks or kfrees) between two code paths 
and confirms that the inconsistent operations are not recovered in the
current function or the callers, so they constitute bugs. 

Note that, as a bug found by static analysis, it can be a false
positive or hard to trigger. Multiple researchers have cross-reviewed
the bug.

 drivers/media/platform/ti-vpe/cal-video.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/media/platform/ti-vpe/cal-video.c b/drivers/media/platform/ti-vpe/cal-video.c
index 7799da1cc261..3e936a2ca36c 100644
--- a/drivers/media/platform/ti-vpe/cal-video.c
+++ b/drivers/media/platform/ti-vpe/cal-video.c
@@ -823,6 +823,9 @@ static int cal_ctx_v4l2_init_formats(struct cal_ctx *ctx)
 	/* Enumerate sub device formats and enable all matching local formats */
 	ctx->active_fmt = devm_kcalloc(ctx->cal->dev, cal_num_formats,
 				       sizeof(*ctx->active_fmt), GFP_KERNEL);
+	if (!ctx->active_fmt)
+		return -ENOMEM;
+
 	ctx->num_active_fmt = 0;
 
 	for (j = 0, i = 0; ; ++j) {
-- 
2.25.1