[PATCH] media: meson: Add NULL check after the call to kmalloc()

[PATCH] media: meson: Add NULL check after the call to kmalloc()

[Austin Kim]

If the kmalloc() return NULL, the NULL pointer dereference will occur.
	new_ts->ts = ts;

Add exception check after the call to kmalloc() is made.

Signed-off-by: Austin Kim <austindh.kim@gmail.com>
---
 drivers/staging/media/meson/vdec/vdec_helpers.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/drivers/staging/media/meson/vdec/vdec_helpers.c b/drivers/staging/media/meson/vdec/vdec_helpers.c
index f16948b..e7e56d5 100644
--- a/drivers/staging/media/meson/vdec/vdec_helpers.c
+++ b/drivers/staging/media/meson/vdec/vdec_helpers.c
@@ -206,6 +206,10 @@ void amvdec_add_ts_reorder(struct amvdec_session *sess, u64 ts, u32 offset)
 	unsigned long flags;
 
 	new_ts = kmalloc(sizeof(*new_ts), GFP_KERNEL);
+	if (!new_ts) {
+		dev_err(sess->core->dev, "Failed to kmalloc()\n");
+		return;
+	}
 	new_ts->ts = ts;
 	new_ts->offset = offset;
 
-- 
2.6.2

Re: [PATCH] media: meson: Add NULL check after the call to kmalloc()

[Rasmus Villemoes]

On 04/09/2019 10.22, Austin Kim wrote:
> If the kmalloc() return NULL, the NULL pointer dereference will occur.
> 	new_ts->ts = ts;
> 
> Add exception check after the call to kmalloc() is made.
> 
> Signed-off-by: Austin Kim <austindh.kim@gmail.com>
> ---
>  drivers/staging/media/meson/vdec/vdec_helpers.c | 4 ++++
>  1 file changed, 4 insertions(+)
> 
> diff --git a/drivers/staging/media/meson/vdec/vdec_helpers.c b/drivers/staging/media/meson/vdec/vdec_helpers.c
> index f16948b..e7e56d5 100644
> --- a/drivers/staging/media/meson/vdec/vdec_helpers.c
> +++ b/drivers/staging/media/meson/vdec/vdec_helpers.c
> @@ -206,6 +206,10 @@ void amvdec_add_ts_reorder(struct amvdec_session *sess, u64 ts, u32 offset)
>  	unsigned long flags;
>  
>  	new_ts = kmalloc(sizeof(*new_ts), GFP_KERNEL);
> +	if (!new_ts) {
> +		dev_err(sess->core->dev, "Failed to kmalloc()\n");
> +		return;
> +	}
>  	new_ts->ts = ts;
>  	new_ts->offset = offset;

No need to printk() on error, AFAIK the mm subsystem should already make
some noise if an allocation fails.
This is not a proper fix - you need to make the function return an error
(-ENOMEM) to let the caller know allocation failed, and allow that to
propagate the error. There's only one caller, which already seems
capable of returning errors (there's an -EAGAIN), so it shouldn't be
that hard - though of course one needs to undo what has been done so far.

Also, unrelated to the kmalloc() handling: amvdec_add_ts_reorder() could
be moved to esparser.c and made static, or at the very least the
EXPORT_SYMBOL can be removed since vdec_helpers.o is linked in to the
same module as the sole user. That probably goes for all the
EXPORT_SYMBOL(amvdec_*).

Rasmus

Re: [PATCH] media: meson: Add NULL check after the call to kmalloc()

[Greg KH]

On Wed, Sep 04, 2019 at 05:22:32PM +0900, Austin Kim wrote:
> If the kmalloc() return NULL, the NULL pointer dereference will occur.
> 	new_ts->ts = ts;
> 
> Add exception check after the call to kmalloc() is made.
> 
> Signed-off-by: Austin Kim <austindh.kim@gmail.com>
> ---
>  drivers/staging/media/meson/vdec/vdec_helpers.c | 4 ++++
>  1 file changed, 4 insertions(+)
> 
> diff --git a/drivers/staging/media/meson/vdec/vdec_helpers.c b/drivers/staging/media/meson/vdec/vdec_helpers.c
> index f16948b..e7e56d5 100644
> --- a/drivers/staging/media/meson/vdec/vdec_helpers.c
> +++ b/drivers/staging/media/meson/vdec/vdec_helpers.c
> @@ -206,6 +206,10 @@ void amvdec_add_ts_reorder(struct amvdec_session *sess, u64 ts, u32 offset)
>  	unsigned long flags;
>  
>  	new_ts = kmalloc(sizeof(*new_ts), GFP_KERNEL);
> +	if (!new_ts) {
> +		dev_err(sess->core->dev, "Failed to kmalloc()\n");

Did you run this through checkpatch?  I think it will say that this line
is not ok.

> +		return;

Shouldn't you return an -ENOMEM error somehow?

thanks,

greg k-h

Re: [PATCH] media: meson: Add NULL check after the call to kmalloc()

[Austin Kim]

2019년 9월 4일 (수) 오후 5:45, Greg KH <gregkh@linuxfoundation.org>님이 작성:
>
> On Wed, Sep 04, 2019 at 05:22:32PM +0900, Austin Kim wrote:
> > If the kmalloc() return NULL, the NULL pointer dereference will occur.
> >       new_ts->ts = ts;
> >
> > Add exception check after the call to kmalloc() is made.
> >
> > Signed-off-by: Austin Kim <austindh.kim@gmail.com>
> > ---
> >  drivers/staging/media/meson/vdec/vdec_helpers.c | 4 ++++
> >  1 file changed, 4 insertions(+)
> >
> > diff --git a/drivers/staging/media/meson/vdec/vdec_helpers.c b/drivers/staging/media/meson/vdec/vdec_helpers.c
> > index f16948b..e7e56d5 100644
> > --- a/drivers/staging/media/meson/vdec/vdec_helpers.c
> > +++ b/drivers/staging/media/meson/vdec/vdec_helpers.c
> > @@ -206,6 +206,10 @@ void amvdec_add_ts_reorder(struct amvdec_session *sess, u64 ts, u32 offset)
> >       unsigned long flags;
> >
> >       new_ts = kmalloc(sizeof(*new_ts), GFP_KERNEL);
> > +     if (!new_ts) {
> > +             dev_err(sess->core->dev, "Failed to kmalloc()\n");
>
> Did you run this through checkpatch?  I think it will say that this line
> is not ok.
>
> > +             return;
>
> Shouldn't you return an -ENOMEM error somehow?

I agreed with your feedback.
Let me take a look at the code more and then resend the patch if necessary.

Thanks,
Austin Kim
>
> thanks,
>
> greg k-h

Re: [PATCH] media: meson: Add NULL check after the call to kmalloc()

[Austin Kim]

2019년 9월 4일 (수) 오후 5:43, Rasmus Villemoes <linux@rasmusvillemoes.dk>님이 작성:
>
> On 04/09/2019 10.22, Austin Kim wrote:
> > If the kmalloc() return NULL, the NULL pointer dereference will occur.
> >       new_ts->ts = ts;
> >
> > Add exception check after the call to kmalloc() is made.
> >
> > Signed-off-by: Austin Kim <austindh.kim@gmail.com>
> > ---
> >  drivers/staging/media/meson/vdec/vdec_helpers.c | 4 ++++
> >  1 file changed, 4 insertions(+)
> >
> > diff --git a/drivers/staging/media/meson/vdec/vdec_helpers.c b/drivers/staging/media/meson/vdec/vdec_helpers.c
> > index f16948b..e7e56d5 100644
> > --- a/drivers/staging/media/meson/vdec/vdec_helpers.c
> > +++ b/drivers/staging/media/meson/vdec/vdec_helpers.c
> > @@ -206,6 +206,10 @@ void amvdec_add_ts_reorder(struct amvdec_session *sess, u64 ts, u32 offset)
> >       unsigned long flags;
> >
> >       new_ts = kmalloc(sizeof(*new_ts), GFP_KERNEL);
> > +     if (!new_ts) {
> > +             dev_err(sess->core->dev, "Failed to kmalloc()\n");
> > +             return;
> > +     }
> >       new_ts->ts = ts;
> >       new_ts->offset = offset;
>
> No need to printk() on error, AFAIK the mm subsystem should already make
> some noise if an allocation fails.

Thanks for valuable feedback.
BTW, if the kmalloc return NULL, mm subsystem throws error log with 100%?
If no, please share error signature of kernel.

> This is not a proper fix - you need to make the function return an error
> (-ENOMEM) to let the caller know allocation failed, and allow that to
> propagate the error. There's only one caller, which already seems
> capable of returning errors (there's an -EAGAIN), so it shouldn't be
> that hard - though of course one needs to undo what has been done so far.
>
> Also, unrelated to the kmalloc() handling: amvdec_add_ts_reorder() could
> be moved to esparser.c and made static, or at the very least the
> EXPORT_SYMBOL can be removed since vdec_helpers.o is linked in to the
> same module as the sole user. That probably goes for all the
> EXPORT_SYMBOL(amvdec_*).

I agreed with your feedback.
- On memory allocation failure, it should have returned (-ENOMEM)
rather than 'return' statement.
- The call to amvdec_add_ts_reorder() is only made by esparser_queue().

Let me resend the patch if necessary.

Thanks,
Austin Kim
>
> Rasmus