[PATCH v3] media: meson: vdec: Fix a NULL pointer dereference in amvdec_add_ts()

[Zhou Qingyang]

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

Fix this bug by adding a NULL check of new_ts.

This bug was found by a static analyzer[1].

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 at umn.edu>
---

[1] 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.

Changes in v3:
  -  Change the description of patch
  -  Turn the return type from 'void' to 'int'
  -  Check the return value in the caller 'esparser_queue()'

Changes in v2:
  -  Delete dev_err() message

 drivers/staging/media/meson/vdec/esparser.c     | 7 ++++++-
 drivers/staging/media/meson/vdec/vdec_helpers.c | 8 ++++++--
 drivers/staging/media/meson/vdec/vdec_helpers.h | 4 ++--
 3 files changed, 14 insertions(+), 5 deletions(-)

diff --git a/drivers/staging/media/meson/vdec/esparser.c b/drivers/staging/media/meson/vdec/esparser.c
index db7022707ff8..095100a50da8 100644
--- a/drivers/staging/media/meson/vdec/esparser.c
+++ b/drivers/staging/media/meson/vdec/esparser.c
@@ -328,7 +328,12 @@ esparser_queue(struct amvdec_session *sess, struct vb2_v4l2_buffer *vbuf)
 
 	offset = esparser_get_offset(sess);
 
-	amvdec_add_ts(sess, vb->timestamp, vbuf->timecode, offset, vbuf->flags);
+	ret = amvdec_add_ts(sess, vb->timestamp, vbuf->timecode, offset, vbuf->flags);
+	if (!ret) {
+		v4l2_m2m_buf_done(vbuf, VB2_BUF_STATE_ERROR);
+		return ret;
+	}
+
 	dev_dbg(core->dev, "esparser: ts = %llu pld_size = %u offset = %08X flags = %08X\n",
 		vb->timestamp, payload_size, offset, vbuf->flags);
 
diff --git a/drivers/staging/media/meson/vdec/vdec_helpers.c b/drivers/staging/media/meson/vdec/vdec_helpers.c
index b9125c295d1d..06fd66539797 100644
--- a/drivers/staging/media/meson/vdec/vdec_helpers.c
+++ b/drivers/staging/media/meson/vdec/vdec_helpers.c
@@ -227,13 +227,16 @@ int amvdec_set_canvases(struct amvdec_session *sess,
 }
 EXPORT_SYMBOL_GPL(amvdec_set_canvases);
 
-void amvdec_add_ts(struct amvdec_session *sess, u64 ts,
-		   struct v4l2_timecode tc, u32 offset, u32 vbuf_flags)
+int amvdec_add_ts(struct amvdec_session *sess, u64 ts,
+		  struct v4l2_timecode tc, u32 offset, u32 vbuf_flags)
 {
 	struct amvdec_timestamp *new_ts;
 	unsigned long flags;
 
 	new_ts = kzalloc(sizeof(*new_ts), GFP_KERNEL);
+	if (!new_ts)
+		return -ENOMEM;
+
 	new_ts->ts = ts;
 	new_ts->tc = tc;
 	new_ts->offset = offset;
@@ -242,6 +245,7 @@ void amvdec_add_ts(struct amvdec_session *sess, u64 ts,
 	spin_lock_irqsave(&sess->ts_spinlock, flags);
 	list_add_tail(&new_ts->list, &sess->timestamps);
 	spin_unlock_irqrestore(&sess->ts_spinlock, flags);
+	return 0;
 }
 EXPORT_SYMBOL_GPL(amvdec_add_ts);
 
diff --git a/drivers/staging/media/meson/vdec/vdec_helpers.h b/drivers/staging/media/meson/vdec/vdec_helpers.h
index 88137d15aa3a..4bf3e61d081b 100644
--- a/drivers/staging/media/meson/vdec/vdec_helpers.h
+++ b/drivers/staging/media/meson/vdec/vdec_helpers.h
@@ -56,8 +56,8 @@ void amvdec_dst_buf_done_offset(struct amvdec_session *sess,
  * @offset: offset in the VIFIFO where the associated packet was written
  * @flags: the vb2_v4l2_buffer flags
  */
-void amvdec_add_ts(struct amvdec_session *sess, u64 ts,
-		   struct v4l2_timecode tc, u32 offset, u32 flags);
+int amvdec_add_ts(struct amvdec_session *sess, u64 ts,
+		  struct v4l2_timecode tc, u32 offset, u32 flags);
 void amvdec_remove_ts(struct amvdec_session *sess, u64 ts);
 
 /**
-- 
2.25.1