[PATCH] drm/scheduler: Add missing RCU flag to fence slab

[Rob Clark]

From: Rob Clark <robdclark@xxxxxxxxxxxx>

Fixes the KASAN splat:

   ==================================================================
   BUG: KASAN: use-after-free in msm_ioctl_wait_fence+0x31c/0x7b0
   Read of size 4 at addr ffffff808cb7c2f8 by task syz-executor/12236
   CPU: 6 PID: 12236 Comm: syz-executor Tainted: G        W         5.15.119-lockdep-19932-g4a017c53fe63 #1 b15455e5b94c63032dd99eb0190c27e582b357ed
   Hardware name: Google Homestar (rev3) (DT)
   Call trace:
    dump_backtrace+0x0/0x4e8
    show_stack+0x34/0x50
    dump_stack_lvl+0xdc/0x11c
    print_address_description+0x30/0x2d8
    kasan_report+0x178/0x1e4
    kasan_check_range+0x1b0/0x1b8
    __kasan_check_read+0x44/0x54
    msm_ioctl_wait_fence+0x31c/0x7b0
    drm_ioctl_kernel+0x214/0x418
    drm_ioctl+0x524/0xbe8
    __arm64_sys_ioctl+0x154/0x1d0
    invoke_syscall+0x98/0x278
    el0_svc_common+0x214/0x274
    do_el0_svc+0x9c/0x19c
    el0_svc+0x5c/0xc0
    el0t_64_sync_handler+0x78/0x108
    el0t_64_sync+0x1a4/0x1a8
   Allocated by task 12224:
    kasan_save_stack+0x38/0x68
    __kasan_slab_alloc+0x6c/0x88
    kmem_cache_alloc+0x1b8/0x428
    drm_sched_fence_alloc+0x30/0x94
    drm_sched_job_init+0x7c/0x178
    msm_ioctl_gem_submit+0x2b8/0x5ac4
    drm_ioctl_kernel+0x214/0x418
    drm_ioctl+0x524/0xbe8
    __arm64_sys_ioctl+0x154/0x1d0
    invoke_syscall+0x98/0x278
    el0_svc_common+0x214/0x274
    do_el0_svc+0x9c/0x19c
    el0_svc+0x5c/0xc0
    el0t_64_sync_handler+0x78/0x108
    el0t_64_sync+0x1a4/0x1a8
   Freed by task 32:
    kasan_save_stack+0x38/0x68
    kasan_set_track+0x28/0x3c
    kasan_set_free_info+0x28/0x4c
    ____kasan_slab_free+0x110/0x164
    __kasan_slab_free+0x18/0x28
    kmem_cache_free+0x1e0/0x904
    drm_sched_fence_free_rcu+0x80/0x9c
    rcu_do_batch+0x318/0xcf0
    rcu_nocb_cb_kthread+0x1a0/0xc4c
    kthread+0x2e4/0x3a0
    ret_from_fork+0x10/0x20
   Last potentially related work creation:
    kasan_save_stack+0x38/0x68
    kasan_record_aux_stack+0xd4/0x114
    __call_rcu_common+0xd4/0x1478
    call_rcu+0x1c/0x28
    drm_sched_fence_release_scheduled+0x108/0x158
    dma_fence_release+0x178/0x564
    drm_sched_fence_release_finished+0xb4/0x124
    dma_fence_release+0x178/0x564
    __msm_gem_submit_destroy+0x150/0x488
    msm_job_free+0x9c/0xdc
    drm_sched_main+0xec/0x9ac
    kthread+0x2e4/0x3a0
    ret_from_fork+0x10/0x20
   Second to last potentially related work creation:
    kasan_save_stack+0x38/0x68
    kasan_record_aux_stack+0xd4/0x114
    __call_rcu_common+0xd4/0x1478
    call_rcu+0x1c/0x28
    drm_sched_fence_release_scheduled+0x108/0x158
    dma_fence_release+0x178/0x564
    drm_sched_fence_release_finished+0xb4/0x124
    dma_fence_release+0x178/0x564
    drm_sched_entity_fini+0x170/0x238
    drm_sched_entity_destroy+0x34/0x44
    __msm_file_private_destroy+0x60/0x118
    msm_submitqueue_destroy+0xd0/0x110
    __msm_gem_submit_destroy+0x384/0x488
    retire_submits+0x6a8/0xa14
    recover_worker+0x764/0xa50
    kthread_worker_fn+0x3f4/0x9ec
    kthread+0x2e4/0x3a0
    ret_from_fork+0x10/0x20
   The buggy address belongs to the object at ffffff808cb7c280
   The buggy address is located 120 bytes inside of
   The buggy address belongs to the page:
   page:000000008b01d27d refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x10cb7c
   head:000000008b01d27d order:1 compound_mapcount:0
   flags: 0x8000000000010200(slab|head|zone=2)
   raw: 8000000000010200 fffffffe06844d80 0000000300000003 ffffff80860dca00
   raw: 0000000000000000 0000000000190019 00000001ffffffff 0000000000000000
   page dumped because: kasan: bad access detected
   Memory state around the buggy address:
    ffffff808cb7c180: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
    ffffff808cb7c200: 00 00 00 00 00 fc fc fc fc fc fc fc fc fc fc fc
   >ffffff808cb7c280: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                                                                   ^
    ffffff808cb7c300: fb fb fb fb fb fb fb fb fb fb fb fb fb fc fc fc
    ffffff808cb7c380: fc fc fc fc fc fc fc fc 00 00 00 00 00 00 00 00
   ==================================================================

Suggested-by: Alexander Potapenko <glider@xxxxxxxxxx>
Signed-off-by: Rob Clark <robdclark@xxxxxxxxxxxx>
---
 drivers/gpu/drm/scheduler/sched_fence.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/scheduler/sched_fence.c b/drivers/gpu/drm/scheduler/sched_fence.c
index ef120475e7c6..b624711c6e03 100644
--- a/drivers/gpu/drm/scheduler/sched_fence.c
+++ b/drivers/gpu/drm/scheduler/sched_fence.c
@@ -35,7 +35,7 @@ static int __init drm_sched_fence_slab_init(void)
 {
 	sched_fence_slab = kmem_cache_create(
 		"drm_sched_fence", sizeof(struct drm_sched_fence), 0,
-		SLAB_HWCACHE_ALIGN, NULL);
+		SLAB_HWCACHE_ALIGN | SLAB_TYPESAFE_BY_RCU, NULL);
 	if (!sched_fence_slab)
 		return -ENOMEM;
 
-- 
2.41.0