[PATCH 0/3] nouveau: fix 3 null-ptr derefs

[PATCH 0/3] nouveau: fix 3 null-ptr derefs

[Jim Cromie via B4 Relay]

These 3 patches fix NULL ptr derefs I hit while booting kernels with
unrelated work (dynamic-debug) on a 2019 amdgpu+noueau laptop.  One of
them is possibly hard to reproduce, the others are "dependable".

Signed-off-by: Jim Cromie <jim.cromie@gmail.com>
---
Jim Cromie (3):
      drm/nouveau: Fix NULL pointer dereferences in GETPARAM ioctl
      drm/nouveau: Fix NULL pointer dereference in GET_ZCULL_INFO ioctl
      drm/nouveau/gsp: Fix NULL dereference in nvkm_gsp_gcx_ready()

 drivers/gpu/drm/nouveau/nouveau_abi16.c           | 27 ++++++++++++++++++-----
 drivers/gpu/drm/nouveau/nvkm/engine/device/user.c |  2 +-
 drivers/gpu/drm/nouveau/nvkm/subdev/gsp/base.c    |  2 +-
 3 files changed, 24 insertions(+), 7 deletions(-)
---
base-commit: 72d3fcf802c45d00b300f25b848a93c3a2bd7c7e
change-id: 20261002-my-fixups-324d25f3bd05

Best regards,
-- 
Jim Cromie <jim.cromie@gmail.com>

[PATCH 1/3] drm/nouveau: Fix NULL pointer dereferences in GETPARAM ioctl

[Jim Cromie via B4 Relay]

From: Jim Cromie <jim.cromie@gmail.com>

When hardware or firmware initialization fails, the graphics engine
(gr) or device functions may remain NULL. Attempting to access these
during the GETPARAM ioctl (e.g., NOUVEAU_GETPARAM_GRAPH_UNITS) results
in a kernel NULL pointer dereference, causing a crash when userspace
(GNOME/Mesa) attempts to probe the device.

Add safety checks for 'gr', 'gr->func', and 'nvkm_device->func' in the
ioctl handler. Return -ENODEV to signal the missing hardware state to
userspace, and use NV_ERROR_ONCE to provide diagnostic proof in the
kernel log without risking a console flood.

NOTE:

I encountered these crashes while booting unrelated code (in
dynamic-debug) on real HW.  There was also some fwupd updates around
this time, so it could all be transient/unreproducible.  But it did
happen, and could happen again in unforseen circumstances.

Signed-off-by: Jim Cromie <jim.cromie@gmail.com>
---
 drivers/gpu/drm/nouveau/nouveau_abi16.c | 25 +++++++++++++++++++++----
 1 file changed, 21 insertions(+), 4 deletions(-)

diff --git a/drivers/gpu/drm/nouveau/nouveau_abi16.c b/drivers/gpu/drm/nouveau/nouveau_abi16.c
index 4542d5f4ded8..cb1810dee8e5 100644
--- a/drivers/gpu/drm/nouveau/nouveau_abi16.c
+++ b/drivers/gpu/drm/nouveau/nouveau_abi16.c
@@ -306,7 +306,12 @@ nouveau_abi16_ioctl_getparam(ABI16_IOCTL_ARGS)
 		getparam->value = 1;
 		break;
 	case NOUVEAU_GETPARAM_GRAPH_UNITS:
-		getparam->value = nvkm_gr_units(gr);
+		if (gr && gr->func) {
+			getparam->value = nvkm_gr_units(gr);
+		} else {
+			NV_ERROR_ONCE(drm, "GETPARAM_GRAPH_UNITS: no gr engine or func\n");
+			return -ENODEV;
+		}
 		break;
 	case NOUVEAU_GETPARAM_EXEC_PUSH_MAX: {
 		int ib_max = getparam_dma_ib_max(device);
@@ -315,11 +320,23 @@ nouveau_abi16_ioctl_getparam(ABI16_IOCTL_ARGS)
 		break;
 	}
 	case NOUVEAU_GETPARAM_VRAM_BAR_SIZE:
-		getparam->value = nvkm_device->func->resource_size(nvkm_device, NVKM_BAR1_FB);
+		if (nvkm_device && nvkm_device->func && nvkm_device->func->resource_size) {
+			getparam->value =
+				nvkm_device->func->resource_size(nvkm_device, NVKM_BAR1_FB);
+		} else {
+			NV_ERROR_ONCE(drm, "GETPARAM_VRAM_BAR_SIZE: no device func\n");
+			return -ENODEV;
+		}
 		break;
 	case NOUVEAU_GETPARAM_VRAM_USED: {
-		struct ttm_resource_manager *vram_mgr = ttm_manager_type(&drm->ttm.bdev, TTM_PL_VRAM);
-		getparam->value = (u64)ttm_resource_manager_usage(vram_mgr);
+		struct ttm_resource_manager *vram_mgr =
+			ttm_manager_type(&drm->ttm.bdev, TTM_PL_VRAM);
+		if (vram_mgr) {
+			getparam->value = (u64)ttm_resource_manager_usage(vram_mgr);
+		} else {
+			NV_ERROR_ONCE(drm, "GETPARAM_VRAM_USED: no vram mgr\n");
+			return -ENODEV;
+		}
 		break;
 	}
 	case NOUVEAU_GETPARAM_HAS_VMA_TILEMODE:

-- 
2.55.0

[PATCH 2/3] drm/nouveau: Fix NULL pointer dereference in GET_ZCULL_INFO ioctl

[Jim Cromie via B4 Relay]

From: Jim Cromie <jim.cromie@gmail.com>

When graphics engine firmware fails to load or initialization aborts
early, nvxx_gr(drm) returns NULL. Calling DRM_IOCTL_NOUVEAU_GET_ZCULL_INFO
causes nouveau_abi16_ioctl_get_zcull_info() to dereference gr at offset
0xf0 without checking for NULL, triggering a kernel page fault.

Validate that gr is non-NULL before inspecting gr->has_zcull_info.

Signed-off-by: Jim Cromie <jim.cromie@gmail.com>
---
Aug 14 09:21:52 frodo kernel: BUG: kernel NULL pointer dereference, address: 00000000000000f0
Aug 14 09:21:52 frodo kernel: #PF: error_code(0x0000) - not-present page
Aug 14 09:21:52 frodo kernel: Oops: Oops: 0000 [#1] SMP NOPTI
Aug 14 09:21:52 frodo kernel: RIP: 0010:nouveau_abi16_ioctl_get_zcull_info+0x17/0xa0 [nouveau]
Aug 14 09:21:52 frodo kernel: Code: 00 00 00 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 f3 0f 1e fa 0f 1f 44 00 00 48 8b 47 40 48 8b 00 48 8b 80 70 02 00 00 <80> b8 f0 00 00 00 00 74 72 8b 90 c0 00 00 00 89 16 8b 90 c4 00 00
Aug 14 09:21:52 frodo kernel: Call Trace:
Aug 14 09:21:52 frodo kernel:  <TASK>
Aug 14 09:21:52 frodo kernel:  drm_ioctl_kernel+0xae/0x100
Aug 14 09:21:52 frodo kernel:  drm_ioctl+0x2e0/0x560
Aug 14 09:21:52 frodo kernel:  ? __pfx_nouveau_abi16_ioctl_get_zcull_info+0x10/0x10 [nouveau]
Aug 14 09:21:52 frodo kernel:  nouveau_drm_ioctl+0x58/0xc0 [nouveau]
Aug 14 09:21:52 frodo kernel:  __x64_sys_ioctl+0xb9/0x100
Aug 14 09:21:52 frodo kernel:  do_syscall_64+0xe2/0x560
Aug 14 09:21:52 frodo kernel:  entry_SYSCALL_64_after_hwframe+0x76/0x7e
Aug 14 09:21:52 frodo kernel:  </TASK>
---
 drivers/gpu/drm/nouveau/nouveau_abi16.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/nouveau/nouveau_abi16.c b/drivers/gpu/drm/nouveau/nouveau_abi16.c
index cb1810dee8e5..0871ac025ace 100644
--- a/drivers/gpu/drm/nouveau/nouveau_abi16.c
+++ b/drivers/gpu/drm/nouveau/nouveau_abi16.c
@@ -357,7 +357,7 @@ nouveau_abi16_ioctl_get_zcull_info(ABI16_IOCTL_ARGS)
 	struct nvkm_gr *gr = nvxx_gr(drm);
 	struct drm_nouveau_get_zcull_info *out = data;
 
-	if (gr->has_zcull_info) {
+	if (gr && gr->has_zcull_info) {
 		const struct nvkm_gr_zcull_info *i = &gr->zcull_info;
 
 		out->width_align_pixels = i->width_align_pixels;

-- 
2.55.0

[PATCH 3/3] drm/nouveau/gsp: Fix NULL dereference in nvkm_gsp_gcx_ready()

[Jim Cromie via B4 Relay]

From: Jim Cromie <jim.cromie@gmail.com>

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.

On GPUs running without GSP-RM (e.g. Volta GV100, NvGspRm=0, 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:

  RIP: 0010:nvkm_gsp_gcx_ready+0x10/0x30 [nouveau]
  Code: ... 48 8b 87 70 0e 00 00 <48> 8b 40 18 ...
  RAX: 0000000000000000 RDI: ffff8c9555fca000
  Call Trace:
   nvkm_udevice_mthd+0xa5/0x150 [nouveau]
   nvkm_ioctl+0xcc/0x1d0 [nouveau]
   nvif_object_mthd+0x110/0x1e0 [nouveau]
   nvif_device_gcx_ready+0x36/0x60 [nouveau]
   nouveau_pmops_runtime_suspend+0x39/0x140 [nouveau]

Instruction decode shows `mov rax, [rdi+0xe70]` loads gsp->rm (0x0),
and `<48> 8b 40 18` (`mov rax, [rax+0x18]`) faults accessing rm->api.

Fix by:
0. Checking !nvkm_gsp_rm(gsp) in nvkm_udevice_gcx_ready() so non-RM
   devices report GC6/GcOff ready and bypass the GSP call entirely.
1. Guarding gsp and gsp->rm in nvkm_gsp_gcx_ready() before inspecting
   gsp->rm->api->gsp->gcx_ready.

Fixes: cb4c7603678c ("drm/nouveau/gsp/r570: Add support for INTERNAL_GCX_ENTRY_PREREQUISITE")
Signed-off-by: Jim Cromie <jim.cromie@gmail.com>
---
 drivers/gpu/drm/nouveau/nvkm/engine/device/user.c | 2 +-
 drivers/gpu/drm/nouveau/nvkm/subdev/gsp/base.c    | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

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)
 	} *args = data;
 	int ret = -ENOSYS;
 
-	if (!gsp) {
+	if (!nvkm_gsp_rm(gsp)) {
 		args->v0.ready = NV_DEVICE_GC6_READY | NV_DEVICE_GCOFF_READY;
 		return 0;
 	}
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)
 int
 nvkm_gsp_gcx_ready(struct nvkm_gsp *gsp)
 {
-	if (!gsp->rm->api->gsp->gcx_ready)
+	if (!gsp || !gsp->rm || !gsp->rm->api->gsp->gcx_ready)
 		return NV_DEVICE_GC6_READY | NV_DEVICE_GCOFF_READY;
 
 	return gsp->rm->api->gsp->gcx_ready(gsp);

-- 
2.55.0

Re: [PATCH 0/3] nouveau: fix 3 null-ptr derefs

[Daniel Campos Ramos]

Hi Jim,

I tested patches 1/3 and 2/3 on 7.3.0-rc1, with an RTX 3060 (GA106)
passed through to a VM (vfio-pci). Patch 3/3 does not apply on 7.3-rc1
(nvkm_gsp_gcx_ready() is not there yet), so it is untested here.

Without firmware (the whole nvidia/ga106 folder removed and the
initramfs rebuilt), nouveau reports acr, gr and sec2 "firmware
unavailable", so there is no GR engine:

- GETPARAM with NOUVEAU_GETPARAM_GRAPH_UNITS returns -ENODEV and logs
  "GETPARAM_GRAPH_UNITS: no gr engine or func"; the desktop session
  already reached that path at boot.
- DRM_IOCTL_NOUVEAU_GET_ZCULL_INFO returns -ENOTTY.

I also called both ioctls directly from a small test program on the
render node. No oops anywhere: KWin composites, NVK declines the device
and zink falls back to llvmpipe.

With the firmware restored, GSP-RM 570.144 loads, there is no oops, and
the card drives a Sony 3D TV in every HDMI 1.4 3D structure it declares,
at 12 bpc.

On your worry about firmware: the most "damaging" thing in all of this
testing was the TV getting stuck on a corrupted signal during an earlier
no-firmware run, solved by power-cycling it and feeding it a proper
signal. No GPU firmware is ever written, and the firmware files in the
VM are disposable.

The kernel logs, the test program and its output are here:
https://github.com/danielcamposramos/sony-bravia-linux/tree/main/docs/upstream/nouveau-null-v3-test-2026-10-03

Tested-by: Daniel Campos Ramos <Capitain_Jack@yahoo.com> # 1/3 and 2/3, GA106

The test was run with an AI assistant doing the legwork under my
direction; the results above are what I saw on the hardware.

Daniel

Re: [PATCH 0/3] nouveau: fix 3 null-ptr derefs

[Lyude Paul]

Hi, could you please specify what hardware this is, and why exactly you're
booting it without ACR firmware?

I'm not totally against these patches, but these cards really aren't meant to
be run with the ACR firmware these days. You're going to hit pretty regular
issues and bitrot pretty regularly if we don't just figure out why exactly
it's not loading - could you send a dmesg from when your system boots up so we
could take a look?

On Fri, 2026-10-02 at 12:09 -0600, Jim Cromie via B4 Relay wrote:
> These 3 patches fix NULL ptr derefs I hit while booting kernels with
> unrelated work (dynamic-debug) on a 2019 amdgpu+noueau laptop.  One of
> them is possibly hard to reproduce, the others are "dependable".
> 
> Signed-off-by: Jim Cromie <jim.cromie@gmail.com>
> ---
> Jim Cromie (3):
>       drm/nouveau: Fix NULL pointer dereferences in GETPARAM ioctl
>       drm/nouveau: Fix NULL pointer dereference in GET_ZCULL_INFO ioctl
>       drm/nouveau/gsp: Fix NULL dereference in nvkm_gsp_gcx_ready()
> 
>  drivers/gpu/drm/nouveau/nouveau_abi16.c           | 27 ++++++++++++++++++-----
>  drivers/gpu/drm/nouveau/nvkm/engine/device/user.c |  2 +-
>  drivers/gpu/drm/nouveau/nvkm/subdev/gsp/base.c    |  2 +-
>  3 files changed, 24 insertions(+), 7 deletions(-)
> ---
> base-commit: 72d3fcf802c45d00b300f25b848a93c3a2bd7c7e
> change-id: 20261002-my-fixups-324d25f3bd05
> 
> Best regards,

-- 
Cheers,
 Lyude Paul (she/her)
 Senior Software Engineer at Red Hat

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