linux-kernel - Re: [PATCH] media: meson: vdec: potential dereference of null pointer

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Date:   Thu, 9 Dec 2021 18:52:12 +0100
From:   Neil Armstrong <narmstrong@...libre.com>
To:     Hans Verkuil <hverkuil@...all.nl>,
        Jiasheng Jiang <jiasheng@...as.ac.cn>, mchehab@...nel.org,
        gregkh@...uxfoundation.org, khilman@...libre.com,
        jbrunet@...libre.com, martin.blumenstingl@...glemail.com
Cc:     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: Re: [PATCH] media: meson: vdec: potential dereference of null pointer

Hi,

On 09/12/2021 12:58, Hans Verkuil wrote:
> On 09/12/2021 09:58, Jiasheng Jiang wrote:
>> he return value of kzalloc() needs to be checked.
>> To avoid use of null pointer in case of the failure of alloc.
>>
>> Fixes: 876f123b8956 ("media: meson: vdec: bring up to compliance")
>> Signed-off-by: Jiasheng Jiang <jiasheng@...as.ac.cn>
>> ---
>>  drivers/staging/media/meson/vdec/vdec_helpers.c | 2 ++
>>  1 file changed, 2 insertions(+)
>>
>> diff --git a/drivers/staging/media/meson/vdec/vdec_helpers.c b/drivers/staging/media/meson/vdec/vdec_helpers.c
>> index 7f07a9175815..025885fcfec6 100644
>> --- a/drivers/staging/media/meson/vdec/vdec_helpers.c
>> +++ b/drivers/staging/media/meson/vdec/vdec_helpers.c
>> @@ -234,6 +234,8 @@ 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;
> 
> While this avoids dereferencing a NULL pointer, this error isn't propagated to the
> caller. And I'm not sure if that's right.
> 
> Neil, what should be done in this case?
> 
> Regards,
> 
> 	Hans
> 
>>  	new_ts->ts = ts;
>>  	new_ts->tc = tc;
>>  	new_ts->offset = offset;
>>
> 

Probably something like this:

===================><=============================
diff --git a/drivers/staging/media/meson/vdec/esparser.c b/drivers/staging/media/meson/vdec/esparser.c
index db7022707ff8..df733eff9ac7 100644
--- a/drivers/staging/media/meson/vdec/esparser.c
+++ b/drivers/staging/media/meson/vdec/esparser.c
@@ -328,7 +328,11 @@ 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..593b2ccbece2 100644
--- a/drivers/staging/media/meson/vdec/vdec_helpers.c
+++ b/drivers/staging/media/meson/vdec/vdec_helpers.c
@@ -227,13 +227,15 @@ 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;
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);

 /**