Re: [bug report] drm: Warn about negative sizes when calculating scale factor
On Fri, Oct 20, 2023 at 05:11:24PM +0300, Dan Carpenter wrote:
> On Fri, Oct 20, 2023 at 02:55:37PM +0300, Ville Syrjälä wrote:
> > On Fri, Oct 20, 2023 at 02:39:04PM +0300, Dan Carpenter wrote:
> > > On Wed, Oct 18, 2023 at 05:17:42PM +0300, Dan Carpenter wrote:
> > > > drivers/gpu/drm/drm_rect.c
> > > >134 static int drm_calc_scale(int src, int dst)
> > > >135 {
> > > >136 int scale = 0;
> > > >137
> > > >138 if (WARN_ON(src < 0 || dst < 0))
> > > > ^^^
> > > > These days, with automated fuzz testing, this WARN_ON() is problematic.
> > > > WARN() is considered a kernel bug, and pr_warn() is the hip new way to
> > > > alert the user about issues.
> > >
> > > Btw, a lot of people (Greg claims it's the majority of Linux users)
> > > these days have run kernels with panic on warn enabled so that's another
> > > reason to avoid using WARN_ON() for stuff that it known to be possible.
> >
> > This is not possible, unless there is a serious bug somewhere else.
>
> Ah. That's fine then. This is kunit which is deliberately triggering
> the WARN_ON(). The KASAN testing also deliberately triggers WARN_ON()s
> so it's a necessary thing.
>
> I just wonder if there is some way to mark these kinds of warnings as
> expected. Perhaps we could add a comment in the kunit test?
Is there some kind of tool which looks at a dmesg and can separate out
the intentional stack traces from the others?
regards,
dan carpenter
Re: [bug report] drm: Warn about negative sizes when calculating scale factor
On Fri, Oct 20, 2023 at 02:55:37PM +0300, Ville Syrjälä wrote:
> On Fri, Oct 20, 2023 at 02:39:04PM +0300, Dan Carpenter wrote:
> > On Wed, Oct 18, 2023 at 05:17:42PM +0300, Dan Carpenter wrote:
> > > drivers/gpu/drm/drm_rect.c
> > >134 static int drm_calc_scale(int src, int dst)
> > >135 {
> > >136 int scale = 0;
> > >137
> > >138 if (WARN_ON(src < 0 || dst < 0))
> > > ^^^
> > > These days, with automated fuzz testing, this WARN_ON() is problematic.
> > > WARN() is considered a kernel bug, and pr_warn() is the hip new way to
> > > alert the user about issues.
> >
> > Btw, a lot of people (Greg claims it's the majority of Linux users)
> > these days have run kernels with panic on warn enabled so that's another
> > reason to avoid using WARN_ON() for stuff that it known to be possible.
>
> This is not possible, unless there is a serious bug somewhere else.
Ah. That's fine then. This is kunit which is deliberately triggering
the WARN_ON(). The KASAN testing also deliberately triggers WARN_ON()s
so it's a necessary thing.
I just wonder if there is some way to mark these kinds of warnings as
expected. Perhaps we could add a comment in the kunit test?
regards,
dan carpenter
Re: [bug report] drm: Warn about negative sizes when calculating scale factor
On Fri, Oct 20, 2023 at 02:39:04PM +0300, Dan Carpenter wrote:
> On Wed, Oct 18, 2023 at 05:17:42PM +0300, Dan Carpenter wrote:
> > drivers/gpu/drm/drm_rect.c
> >134 static int drm_calc_scale(int src, int dst)
> >135 {
> >136 int scale = 0;
> >137
> >138 if (WARN_ON(src < 0 || dst < 0))
> > ^^^
> > These days, with automated fuzz testing, this WARN_ON() is problematic.
> > WARN() is considered a kernel bug, and pr_warn() is the hip new way to
> > alert the user about issues.
>
> Btw, a lot of people (Greg claims it's the majority of Linux users)
> these days have run kernels with panic on warn enabled so that's another
> reason to avoid using WARN_ON() for stuff that it known to be possible.
This is not possible, unless there is a serious bug somewhere else.
--
Ville Syrjälä
Intel
Re: [bug report] drm: Warn about negative sizes when calculating scale factor
On Wed, Oct 18, 2023 at 05:17:42PM +0300, Dan Carpenter wrote:
> drivers/gpu/drm/drm_rect.c
>134 static int drm_calc_scale(int src, int dst)
>135 {
>136 int scale = 0;
>137
>138 if (WARN_ON(src < 0 || dst < 0))
> ^^^
> These days, with automated fuzz testing, this WARN_ON() is problematic.
> WARN() is considered a kernel bug, and pr_warn() is the hip new way to
> alert the user about issues.
Btw, a lot of people (Greg claims it's the majority of Linux users)
these days have run kernels with panic on warn enabled so that's another
reason to avoid using WARN_ON() for stuff that it known to be possible.
regards,
dan carpenter
