On Mon, 2022-02-21 at 12:11 +0000, Matthew Auld wrote: > When running the mock selftests we currently blow up with: > > <6> [299.836278] i915: Running > i915_gem_huge_page_mock_selftests/igt_mock_memory_region_huge_pages > <1> [299.836356] BUG: kernel NULL pointer dereference, address: > 00000000000000c8 > <1> [299.836361] #PF: supervisor read access in kernel mode > <1> [299.836364] #PF: error_code(0x0000) - not-present page > <6> [299.836367] PGD 0 P4D 0 > <4> [299.836369] Oops: 0000 [#1] PREEMPT SMP NOPTI > <4> [299.836372] CPU: 1 PID: 1429 Comm: i915_selftest Tainted: G > U 5.17.0-rc4-CI-CI_DRM_11227+ #1 > <4> [299.836376] Hardware name: Intel(R) Client Systems > NUC11TNHi5/NUC11TNBi5, BIOS TNTGL357.0042.2020.1221.1743 12/21/2020 > <4> [299.836380] RIP: 0010:ttm_resource_init+0x57/0x90 [ttm] > <4> [299.836392] RSP: 0018:ffffc90001e4f680 EFLAGS: 00010203 > <4> [299.836395] RAX: 0000000000000000 RBX: ffffc90001e4f708 RCX: > 0000000000000000 > <4> [299.836398] RDX: ffff888116172528 RSI: ffffc90001e4f6f8 RDI: > 0000000000000000 > <4> [299.836401] RBP: ffffc90001e4f6f8 R08: 00000000000001b0 R09: > ffff888116172528 > <4> [299.836403] R10: 0000000000000001 R11: 00000000a4cb2e51 R12: > ffffc90001e4fa90 > <4> [299.836406] R13: ffff888116172528 R14: ffff888130d7f4b0 R15: > ffff888130d7f400 > <4> [299.836409] FS: 00007ff241684500(0000) > GS:ffff88849fe80000(0000) knlGS:0000000000000000 > <4> [299.836412] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 > <4> [299.836416] CR2: 00000000000000c8 CR3: 0000000107b80001 CR4: > 0000000000770ee0 > <4> [299.836418] PKRU: 55555554 > <4> [299.836420] Call Trace: > <4> [299.836422] <TASK> > <4> [299.836423] i915_ttm_buddy_man_alloc+0x68/0x240 [i915] > > ttm_resource_init() now needs to access the bo->bdev, and also wants > to > store the bo reference. Try to keep both working. The mock_bo is a > hack > so we can interface directly with the ttm managers alloc() and free() > hooks for > our mock testing, without invoking other TTM features like eviction, > moves, etc. > > v2: make sure we only touch res->bo if the alloc() returns > successfully > > Closes: https://gitlab.freedesktop.org/drm/intel/-/issues/5123 > Fixes: 0e05fc49c358 ("drm/ttm: add common accounting to the resource > mgr v3") > Signed-off-by: Matthew Auld <matthew.auld@xxxxxxxxx> > Cc: Christian König <christian.koenig@xxxxxxx> > Cc: Thomas Hellström <thomas.hellstrom@xxxxxxxxxxxxxxx> > Acked-by: Christian König <christian.koenig@xxxxxxx> Reviewed-by: Thomas Hellström <thomas.hellstrom@xxxxxxxxxxxxxxx> > --- > drivers/gpu/drm/i915/intel_region_ttm.c | 8 ++++++++ > 1 file changed, 8 insertions(+) > > diff --git a/drivers/gpu/drm/i915/intel_region_ttm.c > b/drivers/gpu/drm/i915/intel_region_ttm.c > index f2b888c16958..7dea07c579aa 100644 > --- a/drivers/gpu/drm/i915/intel_region_ttm.c > +++ b/drivers/gpu/drm/i915/intel_region_ttm.c > @@ -200,11 +200,14 @@ intel_region_ttm_resource_alloc(struct > intel_memory_region *mem, > int ret; > > mock_bo.base.size = size; > + mock_bo.bdev = &mem->i915->bdev; > place.flags = flags; > > ret = man->func->alloc(man, &mock_bo, &place, &res); > if (ret == -ENOSPC) > ret = -ENXIO; > + if (!ret) > + res->bo = NULL; /* Rather blow up, then some uaf */ > return ret ? ERR_PTR(ret) : res; > } > > @@ -219,6 +222,11 @@ void intel_region_ttm_resource_free(struct > intel_memory_region *mem, > struct ttm_resource *res) > { > struct ttm_resource_manager *man = mem->region_private; > + struct ttm_buffer_object mock_bo = {}; > + > + mock_bo.base.size = res->num_pages << PAGE_SHIFT; > + mock_bo.bdev = &mem->i915->bdev; > + res->bo = &mock_bo; > > man->func->free(man, res); > }
