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

[Neil Armstrong <narmstrong@baylibre.com>]

Hi,

On 11/01/2022 14:03, Qingyang Zhou wrote:
> Hi Hans:
> 
> Here I certify that this is an origin patch I wrote. I did not copy Neil's patch, and I did not know his patch.
> 
> Neil, please post your original patch here, so everyone can see both patches.
> 
> Yours 
> Zhou Qingyang.
> 
> On Tue, Jan 11, 2022 at 5:16 PM Hans Verkuil <hverkuil-cisco@xs4all.nl <mailto:hverkuil-cisco@xs4all.nl>> wrote:
> 
>     Zhou Qingyang, this is exactly the patch Neil wrote, except you just stuck your
>     name on it. Not nice.
> 
>     Neil, can you post your patch with your own Signed-off-by, then I'll take that one.
> 
>     Regards,
> 
>             Hans
> 
>     On 15/12/2021 04:35, Zhou Qingyang wrote:
>     > 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@umn.edu <mailto:zhou1615@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);
>     > 
>     >  /**
> 

Let's inspect:

I posted a probable solution the 09/12/2021 in a reply to 20211209085840.2081024-1-jiasheng@iscas.ac.cn :

===================><=============================
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);
===================><=============================


Then the patches were sent:
- 20211210015620.2143555-1-jiasheng@iscas.ac.cn on 10/12/2021
- 20211215033535.40422-1-zhou1615@umn.edu on 15/12/2021

They are extremely close but not similar, mostly indenting differs.

Both patches have the missing final "return 0" in amvdec_add_ts which is missing in my proposal.

But only 20211210015620.2143555-1-jiasheng@iscas.ac.cn has the correct "if (ret)" in esparser_queue().
Patch 20211215033535.40422-1-zhou1615@umn.ed has a wrong "if (!ret)".

But when comparing, 20211215033535.40422-1-zhou1615@umn.edu is an almost exact copy of my proposal, minus the fixes and the bogus return check.

To be honest, there is a limited way to fix this, it's probable 20211215033535.40422-1-zhou1615@umn.edu was written independently from
my proposal since there is a bug return check, and 20211210015620.2143555-1-jiasheng@iscas.ac.cn was rewritten from my proposal.

Since 20211215033535.40422-1-zhou1615@umn.ed has a bogus return check, it should be naked.

I'll only ask 20211210015620.2143555-1-jiasheng@iscas.ac.cn to be resent with a "Suggested-by" and indentation fixed like my proposal.

Neil