[lvc-project] [PATCH] platform/mellanox: mlxreg-hotplug: Check pointer for NULL before dereferencing it
Vadim Pasternak
vadimp at nvidia.com
Tue Mar 5 00:26:42 MSK 2024
> -----Original Message-----
> From: Daniil Dulov <D.Dulov at aladdin.ru>
> Sent: Monday, 4 March 2024 13:44
> To: Vadim Pasternak <vadimp at nvidia.com>; Hans de Goede
> <hdegoede at redhat.com>
> Cc: Mark Gross <mgross at linux.intel.com>; Andy Shevchenko
> <andy at infradead.org>; Darren Hart <dvhart at infradead.org>; platform-
> driver-x86 at vger.kernel.org; linux-kernel at vger.kernel.org; lvc-
> project at linuxtesting.org
> Subject: RE: [PATCH] platform/mellanox: mlxreg-hotplug: Check pointer for
> NULL before dereferencing it
>
> Hello!
>
> I suppose there is no sense to produce dev_err() inside
> mlxreg_hotplug_work_helper() since item is dereferenced twice before we
> call this function. Should we produce dev_err() inside the loop in
> mlxreg_hotplug_work_handler() instead?
Hi Daniil,
I think would be correct just to remove from mlx reg_hotplug_work_helper()
lines validating 'item' pointer.
This is paranoic test, this pointer should never be NULL.
It is safe to remove this validation.
Thanks,
Vadim.
>
> -----Original Message-----
> From: Vadim Pasternak [mailto:vadimp at nvidia.com]
> Sent: Monday, February 26, 2024 6:15 PM
> To: Daniil Dulov <D.Dulov at aladdin.ru>; Hans de Goede
> <hdegoede at redhat.com>
> Cc: Mark Gross <mgross at linux.intel.com>; Andy Shevchenko
> <andy at infradead.org>; Darren Hart <dvhart at infradead.org>; platform-
> driver-x86 at vger.kernel.org; linux-kernel at vger.kernel.org; lvc-
> project at linuxtesting.org
> Subject: RE: [PATCH] platform/mellanox: mlxreg-hotplug: Check pointer for
> NULL before dereferencing it
>
>
>
> > -----Original Message-----
> > From: Daniil Dulov <d.dulov at aladdin.ru>
> > Sent: Monday, 26 February 2024 16:55
> > To: Hans de Goede <hdegoede at redhat.com>
> > Cc: Daniil Dulov <d.dulov at aladdin.ru>; Mark Gross
> > <mgross at linux.intel.com>; Andy Shevchenko <andy at infradead.org>;
> Darren
> > Hart <dvhart at infradead.org>; Vadim Pasternak <vadimp at nvidia.com>;
> > platform-driver-x86 at vger.kernel.org; linux-kernel at vger.kernel.org; lvc-
> > project at linuxtesting.org
> > Subject: [PATCH] platform/mellanox: mlxreg-hotplug: Check pointer for NULL
> > before dereferencing it
> >
> > mlxreg_hotplug_work_helper() implies that item can be NULL. There is a
> > sanity check that checks item for NULL and then dereferences it.
> >
> > Even though, the comment before sanity check says that it can only happen
> if
> > some piece of hardware is broken, but in this case it will lead to NULL-
> pointer
> > dereference before the function is even called, so let's check it before
> > dereferencing.
> >
> > Found by Linux Verification Center (linuxtesting.org) with SVACE.
> >
> > Fixes: c6acad68eb2d ("platform/mellanox: mlxreg-hotplug: Modify to use a
> > regmap interface")
> > Signed-off-by: Daniil Dulov <d.dulov at aladdin.ru>
> > ---
> > drivers/platform/mellanox/mlxreg-hotplug.c | 16 +---------------
> > 1 file changed, 1 insertion(+), 15 deletions(-)
> >
> > diff --git a/drivers/platform/mellanox/mlxreg-hotplug.c
> > b/drivers/platform/mellanox/mlxreg-hotplug.c
> > index 5c022b258f91..524121b9f070 100644
> > --- a/drivers/platform/mellanox/mlxreg-hotplug.c
> > +++ b/drivers/platform/mellanox/mlxreg-hotplug.c
> > @@ -348,20 +348,6 @@ mlxreg_hotplug_work_helper(struct
> > mlxreg_hotplug_priv_data *priv,
> > u32 regval, bit;
> > int ret;
> >
> > - /*
> > - * Validate if item related to received signal type is valid.
> > - * It should never happen, excepted the situation when some
> > - * piece of hardware is broken. In such situation just produce
> > - * error message and return. Caller must continue to handle the
> > - * signals from other devices if any.
> > - */
> > - if (unlikely(!item)) {
> > - dev_err(priv->dev, "False signal: at offset:mask
> > 0x%02x:0x%02x.\n",
> > - item->reg, item->mask);
> > -
> > - return;
> > - }
>
> It would be enough just to produce dev_err(priv->dev, "False signal\n");
> And return.
>
> > -
> > /* Mask event. */
> > ret = regmap_write(priv->regmap, item->reg +
> > MLXREG_HOTPLUG_MASK_OFF,
> > 0);
> > @@ -556,7 +542,7 @@ static void mlxreg_hotplug_work_handler(struct
> > work_struct *work)
> >
> > /* Handle topology and health configuration changes. */
> > for (i = 0; i < pdata->counter; i++, item++) {
> > - if (aggr_asserted & item->aggr_mask) {
> > + if (item && (aggr_asserted & item->aggr_mask)) {
> > if (item->health)
> > mlxreg_hotplug_health_work_helper(priv,
> > item);
> > else
> > --
> > 2.25.1
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