Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
Pre-existing issues: - [High] Possible Use-After-Free of xe_device when a foreign dma-fence signals after device teardown. -- commit 3bd2b743d1b606804ebc5081e49badce29c41a21 Author: Srinivasan Shanmugam <[email protected]> drm/xe: Convert xe_user_fence to drm_user_fence Replace the open-coded user fence implementation in xe_sync.c with the new common drm_user_fence helper. > diff --git a/drivers/gpu/drm/xe/xe_sync.c b/drivers/gpu/drm/xe/xe_sync.c > index 37866768d64c2..2d1e07792506e 100644 > --- a/drivers/gpu/drm/xe/xe_sync.c > +++ b/drivers/gpu/drm/xe/xe_sync.c > @@ -19,36 +18,60 @@ [ ... ] > +static void xe_ufence_worker(struct drm_user_fence *base, bool mm_ok) > +{ > + struct xe_user_fence *ufence = container_of(base, struct xe_user_fence, > base); [ ... ] > + if (mm_ok) { > + if (copy_to_user(ufence->addr, &ufence->value, > sizeof(ufence->value))) > + drm_dbg(&ufence->xe->drm, > + "copy_to_user failed, user fence wasn't > signaled\n"); > + } else { > + drm_dbg(&ufence->xe->drm, > + "mmget_not_zero() failed, ufence wasn't signaled\n"); > + } > + > + wake_up_all(&ufence->xe->ufence_wq); > +} [ ... ] > static struct xe_user_fence *user_fence_create(struct xe_device *xe, u64 > addr, > u64 value) > { > @@ -63,51 +86,22 @@ static struct xe_user_fence *user_fence_create(struct > xe_device *xe, u64 addr, > if (!ufence) > return ERR_PTR(-ENOMEM); > > - ufence->xe = xe; > - kref_init(&ufence->refcount); > - ufence->addr = ptr; > + ufence->xe = xe; > + ufence->addr = ptr; > ufence->value = value; > - ufence->mm = current->mm; > - mmgrab(ufence->mm); > + drm_user_fence_init(&ufence->base, xe->ordered_wq, &xe_ufence_ops); [Severity: High] This is a pre-existing issue, but does this code leave the xe_device vulnerable to a use-after-free when an external dma-fence signals after device teardown? When a user creates a user fence that depends on an external dma-fence (e.g., from amdgpu) by passing a syncobj, xe_sync_entry_parse() creates the user fence without taking a reference to the xe_device. If the user then closes the xe file descriptor or the device is hot-unplugged, the last reference to xe_device can be dropped. xe_sync_entry_cleanup() drops the sync entry's reference to the user fence but does not cancel the pending callback. When the external dma-fence eventually signals, the callback invokes queue_work(). Because the workqueue points to xe->ordered_wq which was already destroyed during device teardown, this causes a UAF crash. If the worker does run, it will also access the freed xe_device pointer in xe_ufence_worker() to wake up waiters. Could user_fence_create() take a reference to the xe_device, or could xe_sync_entry_cleanup() be updated to explicitly cancel the pending callback? > > return ufence; > } -- Sashiko AI review · https://sashiko.dev/#/patchset/[email protected]?part=3
