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X-OriginatorOrg: arm.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 21 Oct 2025 07:16:21.8047 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: 508259a2-4a72-4daf-2b66-08de1071bcdd 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: DB1PEPF000509E6.eurprd03.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: DB4PR08MB9264 On 10/20/25 16:44, Steven Price wrote: > Hi Akash, > > On 20/10/2025 07:00, Akash Goel wrote: >> 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 0000000000000078 >> Mem abort info: >> ESR = 0x0000000096000046 >> EC = 0x25: DABT (current EL), IL = 32 bits >> SET = 0, FnV = 0 >> EA = 0, S1PTW = 0 >> FSC = 0x06: level 2 translation fault >> Data abort info: >> ISV = 0, ISS = 0x00000046, ISS2 = 0x00000000 >> CM = 0, WnR = 1, TnD = 0, TagAccess = 0 >> GCS = 0, Overlay = 0, DirtyBit = 0, Xs = 0 >> user pgtable: 4k pages, 48-bit VAs, pgdp=000000088a863000 >> [000000000000078] pgd=080000088a842003, p4d=080000088a842003, pud=0800000884bf5003, pmd=0000000000000000 >> Internal error: Oops: 0000000096000046 [#1] PREEMPT SMP >> >> pstate: 60000005 (nZCv daif -PAN -UAO -TCO -DIT -SSBS BTYPE=--) >> 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 > > Sorry, perhaps I wasn't very clear. I've already pushed v1 to > drm-misc-fixes (with the fixes line and the R-bs): > > 4eabd0d8791e ("drm/panthor: Fix kernel panic on partial unmap of a GPU VA region") > > Usually there's no need to post another version just to update the tags > as we can do that as part of applying the series. > I am sorry Steve, I am not wel versed with the upstreaming process. > Thanks, > Steve > >> >> 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/panthor/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_op_ctx *op_ctx) >> break; >> >> 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 = 1; >> + vma_count = 2; >> break; >> >> default: >