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X-OriginatorOrg: arm.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 20 Oct 2025 06:01:04.5915 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: aa085df5-0c3b-45b6-4973-08de0f9e0dfa X-MS-Exchange-CrossTenant-Id: f34e5979-57d9-4aaa-ad4d-b122a662184d X-MS-Exchange-CrossTenant-OriginalAttributedTenantConnectingIp: TenantId=f34e5979-57d9-4aaa-ad4d-b122a662184d;Ip=[4.158.2.129];Helo=[outbound-uk1.az.dlp.m.darktrace.com] X-MS-Exchange-CrossTenant-AuthSource: DU6PEPF00009524.eurprd02.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: DB8PR08MB5354 Content-Type: text/plain; charset="utf-8" This commit address a kernel panic issue that can happen if Userspace tries to partially unmap a GPU virtual region (aka drm_gpuva). The VM_BIND interface allows partial unmapping of a BO. Panthor driver pre-allocates memory for the new drm_gpuva structures that would be needed for the map/unmap operation, done using drm_gpuvm layer. It expected that only one new drm_gpuva would be needed on umap but a partial unmap can require 2 new drm_gpuva and that's why it ended up doing a NULL pointer dereference causing a kernel panic. Following dump was seen when partial unmap was exercised. Unable to handle kernel NULL pointer dereference at virtual address 000000= 0000000078 Mem abort info: ESR =3D 0x0000000096000046 EC =3D 0x25: DABT (current EL), IL =3D 32 bits SET =3D 0, FnV =3D 0 EA =3D 0, S1PTW =3D 0 FSC =3D 0x06: level 2 translation fault Data abort info: ISV =3D 0, ISS =3D 0x00000046, ISS2 =3D 0x00000000 CM =3D 0, WnR =3D 1, TnD =3D 0, TagAccess =3D 0 GCS =3D 0, Overlay =3D 0, DirtyBit =3D 0, Xs =3D 0 user pgtable: 4k pages, 48-bit VAs, pgdp=3D000000088a863000 [000000000000078] pgd=3D080000088a842003, p4d=3D080000088a842003, pud=3D08= 00000884bf5003, pmd=3D0000000000000000 Internal error: Oops: 0000000096000046 [#1] PREEMPT SMP pstate: 60000005 (nZCv daif -PAN -UAO -TCO -DIT -SSBS BTYPE=3D--) pc : panthor_gpuva_sm_step_remap+0xe4/0x330 [panthor] lr : panthor_gpuva_sm_step_remap+0x6c/0x330 [panthor] sp : ffff800085d43970 x29: ffff800085d43970 x28: ffff00080363e440 x27: ffff0008090c6000 x26: 0000000000000030 x25: ffff800085d439f8 x24: ffff00080d402000 x23: ffff800085d43b60 x22: ffff800085d439e0 x21: ffff00080abdb180 x20: 0000000000000000 x19: 0000000000000000 x18: 0000000000000010 x17: 6e656c202c303030 x16: 3666666666646466 x15: 393d61766f69202c x14: 312d3d7361203a70 x13: 303030323d6e656c x12: ffff80008324bf58 x11: 0000000000000003 x10: 0000000000000002 x9 : ffff8000801a6a9c x8 : ffff00080360b300 x7 : 0000000000000000 x6 : 000000088aa35fc7 x5 : fff1000080000000 x4 : ffff8000842ddd30 x3 : 0000000000000001 x2 : 0000000100000000 x1 : 0000000000000001 x0 : 0000000000000078 Call trace: panthor_gpuva_sm_step_remap+0xe4/0x330 [panthor] op_remap_cb.isra.22+0x50/0x80 __drm_gpuvm_sm_unmap+0x10c/0x1c8 drm_gpuvm_sm_unmap+0x40/0x60 panthor_vm_exec_op+0xb4/0x3d0 [panthor] panthor_vm_bind_exec_sync_op+0x154/0x278 [panthor] panthor_ioctl_vm_bind+0x160/0x4a0 [panthor] drm_ioctl_kernel+0xbc/0x138 drm_ioctl+0x240/0x500 __arm64_sys_ioctl+0xb0/0xf8 invoke_syscall+0x4c/0x110 el0_svc_common.constprop.1+0x98/0xf8 do_el0_svc+0x24/0x38 el0_svc+0x40/0xf8 el0t_64_sync_handler+0xa0/0xc8 el0t_64_sync+0x174/0x178 Changes in v2: - Add R-bs and fixes tags Fixes: 647810ec2476 ("drm/panthor: Add the MMU/VM logical block") Signed-off-by: Akash Goel Reviewed-by: Boris Brezillon Reviewed-by: Liviu Dudau Reviewed-by: Steven Price --- drivers/gpu/drm/panthor/panthor_mmu.c | 10 +++++++--- 1 file changed, 7 insertions(+), 3 deletions(-) diff --git a/drivers/gpu/drm/panthor/panthor_mmu.c b/drivers/gpu/drm/pantho= r/panthor_mmu.c index 6dec4354e378..7870e7dbaa5d 100644 --- a/drivers/gpu/drm/panthor/panthor_mmu.c +++ b/drivers/gpu/drm/panthor/panthor_mmu.c @@ -1175,10 +1175,14 @@ panthor_vm_op_ctx_prealloc_vmas(struct panthor_vm_o= p_ctx *op_ctx) break; =20 case DRM_PANTHOR_VM_BIND_OP_TYPE_UNMAP: - /* Partial unmaps might trigger a remap with either a prev or a next VA, - * but not both. + /* Two VMAs can be needed for an unmap, as an unmap can happen + * in the middle of a drm_gpuva, requiring a remap with both + * prev & next VA. Or an unmap can span more than one drm_gpuva + * where the first and last ones are covered partially, requring + * a remap for the first with a prev VA and remap for the last + * with a next VA. */ - vma_count =3D 1; + vma_count =3D 2; break; =20 default: --=20 2.25.1