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Thu, 08 Oct 2026 15:19:51 -0700 (PDT) Message-ID: <778d3018e596c0be1db309b5e36aa361db89c9bb.camel@redhat.com> Subject: Re: [PATCH 3/3] drm/nouveau/gsp: Fix NULL dereference in nvkm_gsp_gcx_ready() From: lyude@redhat.com To: jim.cromie@gmail.com, Danilo Krummrich , Maarten Lankhorst , Maxime Ripard , Thomas Zimmermann , David Airlie , Simona Vetter , Dave Airlie Cc: dri-devel@lists.freedesktop.org, nouveau@lists.freedesktop.org, linux-kernel@vger.kernel.org Date: Thu, 08 Oct 2026 18:19:50 -0400 In-Reply-To: <20261002-my-fixups-v1-3-a83d20f9d3fe@gmail.com> References: <20261002-my-fixups-v1-0-a83d20f9d3fe@gmail.com> <20261002-my-fixups-v1-3-a83d20f9d3fe@gmail.com> Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable User-Agent: Evolution 3.58.3 (3.58.3-2.fc43) Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Reviewed-by: Lyude Paul Will push to drm-misc-fixes in a moment, thanks! On Fri, 2026-10-02 at 12:09 -0600, Jim Cromie via B4 Relay wrote: > From: Jim Cromie >=20 > Commit cb4c7603678c ("drm/nouveau/gsp/r570: Add support for > INTERNAL_GCX_ENTRY_PREREQUISITE") hooked nvif_device_gcx_ready() into > nouveau_pmops_runtime_suspend() to consult GSP before runtime > suspend. >=20 > On GPUs running without GSP-RM (e.g. Volta GV100, NvGspRm=3D0, or > missing > GSP firmware blobs), device->gsp is instantiated but gsp->rm remains > NULL. nvkm_udevice_gcx_ready() checked "!gsp" instead of verifying > nvkm_gsp_rm(gsp), allowing non-RM instances to invoke > nvkm_gsp_gcx_ready(). nvkm_gsp_gcx_ready() then unconditionally > dereferenced gsp->rm->api, causing a kernel oops: >=20 > =C2=A0 RIP: 0010:nvkm_gsp_gcx_ready+0x10/0x30 [nouveau] > =C2=A0 Code: ... 48 8b 87 70 0e 00 00 <48> 8b 40 18 ... > =C2=A0 RAX: 0000000000000000 RDI: ffff8c9555fca000 > =C2=A0 Call Trace: > =C2=A0=C2=A0 nvkm_udevice_mthd+0xa5/0x150 [nouveau] > =C2=A0=C2=A0 nvkm_ioctl+0xcc/0x1d0 [nouveau] > =C2=A0=C2=A0 nvif_object_mthd+0x110/0x1e0 [nouveau] > =C2=A0=C2=A0 nvif_device_gcx_ready+0x36/0x60 [nouveau] > =C2=A0=C2=A0 nouveau_pmops_runtime_suspend+0x39/0x140 [nouveau] >=20 > Instruction decode shows `mov rax, [rdi+0xe70]` loads gsp->rm (0x0), > and `<48> 8b 40 18` (`mov rax, [rax+0x18]`) faults accessing rm->api. >=20 > Fix by: > 0. Checking !nvkm_gsp_rm(gsp) in nvkm_udevice_gcx_ready() so non-RM > =C2=A0=C2=A0 devices report GC6/GcOff ready and bypass the GSP call entir= ely. > 1. Guarding gsp and gsp->rm in nvkm_gsp_gcx_ready() before inspecting > =C2=A0=C2=A0 gsp->rm->api->gsp->gcx_ready. >=20 > Fixes: cb4c7603678c ("drm/nouveau/gsp/r570: Add support for > INTERNAL_GCX_ENTRY_PREREQUISITE") > Signed-off-by: Jim Cromie > --- > =C2=A0drivers/gpu/drm/nouveau/nvkm/engine/device/user.c | 2 +- > =C2=A0drivers/gpu/drm/nouveau/nvkm/subdev/gsp/base.c=C2=A0=C2=A0=C2=A0 | = 2 +- > =C2=A02 files changed, 2 insertions(+), 2 deletions(-) >=20 > diff --git a/drivers/gpu/drm/nouveau/nvkm/engine/device/user.c > b/drivers/gpu/drm/nouveau/nvkm/engine/device/user.c > index f78e6b9b4292..d469437eb991 100644 > --- a/drivers/gpu/drm/nouveau/nvkm/engine/device/user.c > +++ b/drivers/gpu/drm/nouveau/nvkm/engine/device/user.c > @@ -201,7 +201,7 @@ nvkm_udevice_gcx_ready(struct nvkm_udevice *udev, > void *data, u32 size) > =C2=A0 } *args =3D data; > =C2=A0 int ret =3D -ENOSYS; > =C2=A0 > - if (!gsp) { > + if (!nvkm_gsp_rm(gsp)) { > =C2=A0 args->v0.ready =3D NV_DEVICE_GC6_READY | > NV_DEVICE_GCOFF_READY; > =C2=A0 return 0; > =C2=A0 } > diff --git a/drivers/gpu/drm/nouveau/nvkm/subdev/gsp/base.c > b/drivers/gpu/drm/nouveau/nvkm/subdev/gsp/base.c > index e475d0e8fa7b..9e07d67dcb0f 100644 > --- a/drivers/gpu/drm/nouveau/nvkm/subdev/gsp/base.c > +++ b/drivers/gpu/drm/nouveau/nvkm/subdev/gsp/base.c > @@ -51,7 +51,7 @@ nvkm_gsp_intr_stall(struct nvkm_gsp *gsp, enum > nvkm_subdev_type type, int inst) > =C2=A0int > =C2=A0nvkm_gsp_gcx_ready(struct nvkm_gsp *gsp) > =C2=A0{ > - if (!gsp->rm->api->gsp->gcx_ready) > + if (!gsp || !gsp->rm || !gsp->rm->api->gsp->gcx_ready) > =C2=A0 return NV_DEVICE_GC6_READY | NV_DEVICE_GCOFF_READY; > =C2=A0 > =C2=A0 return gsp->rm->api->gsp->gcx_ready(gsp);