Fix an oops in ttm_bo_delayed_delete which results from dererencing a dangling pointer: Oops: general protection fault, probably for non-canonical address 0x6b6b6b6b6b6b6b7b: 0000 [#1] PREEMPT SMP CPU: 4 UID: 0 PID: 1082 Comm: kworker/u65:2 Not tainted 6.14.0-rc4-00267-g505460b44513-dirty #216 Hardware name: LENOVO 82N6/LNVNB161216, BIOS GKCN65WW 01/16/2024 Workqueue: ttm ttm_bo_delayed_delete [ttm] RIP: 0010:dma_resv_iter_first_unlocked+0x55/0x290 Code: 31 f6 48 c7 c7 00 2b fa aa e8 97 bd 52 ff e8 a2 c1 53 00 5a 85 c0 74 48 e9 88 01 00 00 4c 89 63 20 4d 85 e4 0f 84 30 01 00 00 <41> 8b 44 24 10 c6 43 2c 01 48 89 df 89 43 28 e8 97 fd ff ff 4c 8b RSP: 0018:ffffbf9383473d60 EFLAGS: 00010202 RAX: 0000000000000001 RBX: ffffbf9383473d88 RCX: 0000000000000000 RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000000 RBP: ffffbf9383473d78 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000000 R12: 6b6b6b6b6b6b6b6b R13: ffffa003bbf78580 R14: ffffa003a6728040 R15: 00000000000383cc FS: 0000000000000000(0000) GS:ffffa00991c00000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 0000758348024dd0 CR3: 000000012c259000 CR4: 0000000000f50ef0 PKRU: 55555554 Call Trace: <TASK> ? __die_body.cold+0x19/0x26 ? die_addr+0x3d/0x70 ? exc_general_protection+0x159/0x460 ? asm_exc_general_protection+0x27/0x30 ? dma_resv_iter_first_unlocked+0x55/0x290 dma_resv_wait_timeout+0x56/0x100 ttm_bo_delayed_delete+0x69/0xb0 [ttm] process_one_work+0x217/0x5c0 worker_thread+0x1c8/0x3d0 ? apply_wqattrs_cleanup.part.0+0xc0/0xc0 kthread+0x10b/0x240 ? kthreads_online_cpu+0x140/0x140 ret_from_fork+0x40/0x70 ? kthreads_online_cpu+0x140/0x140 ret_from_fork_asm+0x11/0x20 </TASK> The cause of this is: - drm_prime_gem_destroy calls dma_buf_put(dma_buf) which releases the reference to the shared dma_buf. The reference count is 0, so the dma_buf is destroyed, which in turn decrements the corresponding amdgpu_bo reference count to 0, and the amdgpu_bo is destroyed - calling drm_gem_object_release then dma_resv_fini (which destroys the reservation object), then finally freeing the amdgpu_bo. - nouveau_bo obj->bo.base.resv is now a dangling pointer to the memory formerly allocated to the amdgpu_bo. - nouveau_gem_object_del calls ttm_bo_put(&nvbo->bo) which calls ttm_bo_release, which schedules ttm_bo_delayed_delete. - ttm_bo_delayed_delete runs and dereferences the dangling resv pointer, resulting in a general protection fault. Fix this by moving the drm_prime_gem_destroy call from nouveau_gem_object_del to nouveau_bo_del_ttm. This ensures that it will be run after ttm_bo_delayed_delete. Signed-off-by: Chris Bainbridge <chris.bainbridge@xxxxxxxxx> Co-Developed-by: Christian König <christian.koenig@xxxxxxx> Link: https://gitlab.freedesktop.org/drm/amd/-/issues/3937 --- drivers/gpu/drm/drm_prime.c | 8 ++++++-- drivers/gpu/drm/nouveau/nouveau_bo.c | 3 +++ drivers/gpu/drm/nouveau/nouveau_gem.c | 3 --- 3 files changed, 9 insertions(+), 5 deletions(-) diff --git a/drivers/gpu/drm/drm_prime.c b/drivers/gpu/drm/drm_prime.c index 32a8781cfd67..4b90fa8954d7 100644 --- a/drivers/gpu/drm/drm_prime.c +++ b/drivers/gpu/drm/drm_prime.c @@ -929,7 +929,9 @@ EXPORT_SYMBOL(drm_gem_prime_export); * &drm_driver.gem_prime_import_sg_table internally. * * Drivers must arrange to call drm_prime_gem_destroy() from their - * &drm_gem_object_funcs.free hook when using this function. + * &ttm_buffer_object.destroy hook when using this function, + * to avoid the dma_buf being freed while the ttm_buffer_object can still + * dereference it. */ struct drm_gem_object *drm_gem_prime_import_dev(struct drm_device *dev, struct dma_buf *dma_buf, @@ -999,7 +1001,9 @@ EXPORT_SYMBOL(drm_gem_prime_import_dev); * implementation in drm_gem_prime_fd_to_handle(). * * Drivers must arrange to call drm_prime_gem_destroy() from their - * &drm_gem_object_funcs.free hook when using this function. + * &ttm_buffer_object.destroy hook when using this function, + * to avoid the dma_buf being freed while the ttm_buffer_object can still + * dereference it. */ struct drm_gem_object *drm_gem_prime_import(struct drm_device *dev, struct dma_buf *dma_buf) diff --git a/drivers/gpu/drm/nouveau/nouveau_bo.c b/drivers/gpu/drm/nouveau/nouveau_bo.c index db961eade225..2016c1e7242f 100644 --- a/drivers/gpu/drm/nouveau/nouveau_bo.c +++ b/drivers/gpu/drm/nouveau/nouveau_bo.c @@ -144,6 +144,9 @@ nouveau_bo_del_ttm(struct ttm_buffer_object *bo) nouveau_bo_del_io_reserve_lru(bo); nv10_bo_put_tile_region(dev, nvbo->tile, NULL); + if (bo->base.import_attach) + drm_prime_gem_destroy(&bo->base, bo->sg); + /* * If nouveau_bo_new() allocated this buffer, the GEM object was never * initialized, so don't attempt to release it. diff --git a/drivers/gpu/drm/nouveau/nouveau_gem.c b/drivers/gpu/drm/nouveau/nouveau_gem.c index 9ae2cee1c7c5..67e3c99de73a 100644 --- a/drivers/gpu/drm/nouveau/nouveau_gem.c +++ b/drivers/gpu/drm/nouveau/nouveau_gem.c @@ -87,9 +87,6 @@ nouveau_gem_object_del(struct drm_gem_object *gem) return; } - if (gem->import_attach) - drm_prime_gem_destroy(gem, nvbo->bo.sg); - ttm_bo_put(&nvbo->bo); pm_runtime_mark_last_busy(dev); -- 2.47.2
