From b74aad23d99b279bb34d135795f39a6d8ecdc075 Mon Sep 17 00:00:00 2001 From: Peiyang He Date: Tue, 8 Sep 2026 20:13:23 +0800 Subject: [PATCH] drm/virtio: fix memory leak of fence event on execbuffer failure virtio_gpu_execbuffer_ioctl() reserves a DRM event with drm_event_reserve_init() when VIRTGPU_EXECBUF_RING_IDX selects a ring that userspace has enabled polling for. virtio_gpu_init_submit() does this before the BO handles, the command buffer, the syncobj arrays and the in-fence are processed, so every later error path runs with the event already pending, including plain argument validation failures such as an invalid bo_handle or an in-syncobj that carries no fence. On those paths, virtio_gpu_cleanup_submit() drops the out-fence without cancelling the event. The fence is freed without ever having been emitted, taking the only driver-side pointer to the event with it. Closing the DRM file does not help. drm_events_release() unlinks pending events but deliberately leaves the freeing to the driver's later drm_send_event(), which never runs for an orphaned event, so the allocation is leaked permanently. Found when fuzzing the virtio driver with Syzkaller: BUG: memory leak unreferenced object 0xffff88802c176e80 (size 96): comm "syz.1.367", pid 10561, jiffies 4294960122 hex dump (first 32 bytes): 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................ c8 6e 17 2c 80 88 ff ff 00 00 00 00 00 00 00 00 .n.,............ backtrace (crc e1973c6b): kmemleak_alloc_recursive include/linux/kmemleak.h:44 [inline] slab_post_alloc_hook mm/slub.c:4597 [inline] slab_alloc_node mm/slub.c:4917 [inline] __kmalloc_cache_noprof+0x49d/0x6f0 mm/slub.c:5485 _kmalloc_noprof include/linux/slab.h:988 [inline] _kzalloc_noprof include/linux/slab.h:1309 [inline] virtio_gpu_fence_event_create drivers/gpu/drm/virtio/virtgpu_submit.c:282 [inline] virtio_gpu_init_submit drivers/gpu/drm/virtio/virtgpu_submit.c:398 [inline] virtio_gpu_execbuffer_ioctl+0xbbf/0x1aa0 drivers/gpu/drm/virtio/virtgpu_submit.c:505 drm_ioctl_kernel+0x1f4/0x3e0 drivers/gpu/drm/drm_ioctl.c:817 drm_ioctl+0x5f4/0xc70 drivers/gpu/drm/drm_ioctl.c:914 vfs_ioctl fs/ioctl.c:51 [inline] __do_sys_ioctl fs/ioctl.c:597 [inline] __se_sys_ioctl fs/ioctl.c:583 [inline] __x64_sys_ioctl+0x18e/0x210 fs/ioctl.c:583 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0x116/0x800 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f Fix by cancelling and freeing the DRM event on the execbuffer error path before dropping the fence. Clear the fence's event pointer after cancellation so it does not retain a dangling pointer. Fixes: cd7f5ca33585 ("drm/virtio: implement context init: add virtio_gpu_fence_event") Cc: stable@vger.kernel.org Signed-off-by: Peiyang He Assisted-by: Codex:gpt-5.6-luna Signed-off-by: Dmitry Osipenko Link: https://patch.msgid.link/D320EAB5680C1411+20260908121323.2405044-1-peiyang_he@smail.nju.edu.cn --- drivers/gpu/drm/virtio/virtgpu_submit.c | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/drivers/gpu/drm/virtio/virtgpu_submit.c b/drivers/gpu/drm/virtio/virtgpu_submit.c index 32cb1e4aa425..734b1e976a75 100644 --- a/drivers/gpu/drm/virtio/virtgpu_submit.c +++ b/drivers/gpu/drm/virtio/virtgpu_submit.c @@ -538,6 +538,10 @@ int virtio_gpu_execbuffer_ioctl(struct drm_device *dev, void *data, virtio_gpu_process_post_deps(&submit); virtio_gpu_complete_submit(&submit); cleanup: + if (ret && submit.out_fence && submit.out_fence->e) { + drm_event_cancel_free(dev, &submit.out_fence->e->base); + submit.out_fence->e = NULL; + } virtio_gpu_cleanup_submit(&submit); return ret;