Hi Chris, Thanks for the fix, few comments below. On Wed, Mar 19, 2025 at 12:54:26PM +0000, Chris Bainbridge wrote: > 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> Then also Christian's SoB is required. > Fixes: https://gitlab.freedesktop.org/drm/amd/-/issues/3937 This is a bug report from amdgpu, but I understand that the same issue applies for nouveau. If at all, this needs to be Closes: https://gitlab.freedesktop.org/drm/amd/-/issues/3937 Maybe you can add a brief comment that this report applies for nouveau as well. Please also add a Fixes: tag that indicates the commit in nouveau that introduced the problem and Cc stable. > --- > 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..452d5c7cd292 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. > + * &drm_gem_object_funcs.free hook or &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. > + * &drm_gem_object_funcs.free hook or &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) Please send a separate commit for the changes in drm_prime.c. > 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 >
