linux-kernel - [PATCH v2] media: meson: vdec: Fix a NULL pointer dereference in amvdec_add

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Message-Id: <20211202160357.75173-1-zhou1615@umn.edu>
Date:   Fri,  3 Dec 2021 00:03:57 +0800
From:   Zhou Qingyang <zhou1615@....edu>
To:     zhou1615@....edu
Cc:     kjlu@....edu, Neil Armstrong <narmstrong@...libre.com>,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Kevin Hilman <khilman@...libre.com>,
        Jerome Brunet <jbrunet@...libre.com>,
        Martin Blumenstingl <martin.blumenstingl@...glemail.com>,
        Hans Verkuil <hverkuil-cisco@...all.nl>,
        Maxime Jourdan <mjourdan@...libre.com>,
        linux-media@...r.kernel.org, linux-amlogic@...ts.infradead.org,
        linux-staging@...ts.linux.dev,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: [PATCH v2] media: meson: vdec: Fix a NULL pointer dereference in amvdec_add_ts()

In amvdec_add_ts(), there is a dereference of kzalloc(), which could lead
to a NULL pointer dereference on failure of kzalloc().

I fix this bug by adding a NULL check of new_ts.

This bug was found by a static analyzer. 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.

Builds with CONFIG_VIDEO_MESON_VDEC=m show no new warnings,
and our static analyzer no longer warns about this code.

Fixes: 876f123b8956 ("media: meson: vdec: bring up to compliance")
Signed-off-by: Zhou Qingyang <zhou1615@....edu>
---
Changes in v2:
  -  Delete dev_err() message

 drivers/staging/media/meson/vdec/vdec_helpers.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/staging/media/meson/vdec/vdec_helpers.c b/drivers/staging/media/meson/vdec/vdec_helpers.c
index b9125c295d1d..ac60514c475b 100644
--- a/drivers/staging/media/meson/vdec/vdec_helpers.c
+++ b/drivers/staging/media/meson/vdec/vdec_helpers.c
@@ -234,6 +234,9 @@ void amvdec_add_ts(struct amvdec_session *sess, u64 ts,
 	unsigned long flags;

 	new_ts = kzalloc(sizeof(*new_ts), GFP_KERNEL);
+	if (!new_ts)
+		return;
+
 	new_ts->ts = ts;
 	new_ts->tc = tc;
 	new_ts->offset = offset;
-- 
2.25.1