[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