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From:   "Zhang, Hawking" <Hawking.Zhang@amd.com>
To:     Denis Arefev <arefev@swemel.ru>,
        "Deucher, Alexander" <Alexander.Deucher@amd.com>
CC:     avid Airlie <airlied@linux.ie>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        "dri-devel@lists.freedesktop.org" <dri-devel@lists.freedesktop.org>,
        "amd-gfx@lists.freedesktop.org" <amd-gfx@lists.freedesktop.org>,
        Daniel Vetter <daniel@ffwll.ch>,
        "Koenig, Christian" <Christian.Koenig@amd.com>
Subject: RE: [PATCH] nbio_v7_4: Add pointer check
Thread-Topic: [PATCH] nbio_v7_4: Add pointer check
Thread-Index: AQHY9ao0+b8BxEO8PESymkR/B234tK45ay9Q
Date:   Fri, 11 Nov 2022 09:03:35 +0000
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References: <20221111074121.23296-1-arefev@swemel.ru>
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[AMD Official Use Only - General]

Hey,

The patch does the right thing from coding principal perspective, but it is=
 really redundant check in RAS context.

The function is a hardware interrupt handler which is only triggered for sp=
ecific RAS event. When software receives the interrupt, the pointer of RAS =
context must be valid one. Otherwise, even the interrupt won't be enabled a=
t all...

Regards,
Hawking

-----Original Message-----
From: amd-gfx <amd-gfx-bounces@lists.freedesktop.org> On Behalf Of Denis Ar=
efev
Sent: Friday, November 11, 2022 15:41
To: Deucher, Alexander <Alexander.Deucher@amd.com>
Cc: avid Airlie <airlied@linux.ie>; linux-kernel@vger.kernel.org; dri-devel=
@lists.freedesktop.org; amd-gfx@lists.freedesktop.org; Daniel Vetter <danie=
l@ffwll.ch>; Koenig, Christian <Christian.Koenig@amd.com>
Subject: [PATCH] nbio_v7_4: Add pointer check

Return value of a function 'amdgpu_ras_find_obj' is dereferenced at nbio_v7=
_4.c:325 without checking for null

Found by Linux Verification Center (linuxtesting.org) with SVACE.

Signed-off-by: Denis Arefev <arefev@swemel.ru>
---
 drivers/gpu/drm/amd/amdgpu/nbio_v7_4.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/gpu/drm/amd/amdgpu/nbio_v7_4.c b/drivers/gpu/drm/amd/a=
mdgpu/nbio_v7_4.c
index eadc9526d33f..0f2ac99de864 100644
--- a/drivers/gpu/drm/amd/amdgpu/nbio_v7_4.c
+++ b/drivers/gpu/drm/amd/amdgpu/nbio_v7_4.c
@@ -304,6 +304,9 @@ static void nbio_v7_4_handle_ras_controller_intr_no_bif=
ring(struct amdgpu_device
 	struct ras_err_data err_data =3D {0, 0, 0, NULL};
 	struct amdgpu_ras *ras =3D amdgpu_ras_get_context(adev);
=20
+	if (!obj)
+	  return;
=20
 	bif_doorbell_intr_cntl =3D RREG32_SOC15(NBIO, 0, mmBIF_DOORBELL_INT_CNTL)=
;
 	if (REG_GET_FIELD(bif_doorbell_intr_cntl,
 		BIF_DOORBELL_INT_CNTL, RAS_CNTLR_INTERRUPT_STATUS)) {
--
2.25.1