Re: [syzbot] [dri?] KASAN: slab-use-after-free Read in drm_gem_object_release_handle

syzbot
2026-04-14T09:04:05Z

Hello,

syzbot has tested the proposed patch but the reproducer is still triggering an issue:
KASAN: slab-use-after-free Read in drm_gem_object_release_handle

==================================================================
BUG: KASAN: slab-use-after-free in drm_gem_object_release_handle+0x47/0x1e0 drivers/gpu/drm/drm_gem.c:374
Read of size 8 at addr ffff8880296c6a88 by task syz.2.83/6856

CPU: 1 UID: 0 PID: 6856 Comm: syz.2.83 Not tainted syzkaller #0 PREEMPT(full)
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 03/18/2026
Call Trace:
<TASK>
dump_stack_lvl+0xe8/0x150 lib/dump_stack.c:120
print_address_description mm/kasan/report.c:378 [inline]
print_report+0xba/0x230 mm/kasan/report.c:482
kasan_report+0x117/0x150 mm/kasan/report.c:595
drm_gem_object_release_handle+0x47/0x1e0 drivers/gpu/drm/drm_gem.c:374
drm_gem_object_release_idr_handle+0x83/0xa0 drivers/gpu/drm/drm_gem.c:404
idr_for_each+0x1c6/0x2a0 lib/idr.c:210
drm_gem_release+0x28/0x40 drivers/gpu/drm/drm_gem.c:1102
drm_file_free+0x729/0xa00 drivers/gpu/drm/drm_file.c:261
drm_close_helper drivers/gpu/drm/drm_file.c:290 [inline]
drm_release+0x2de/0x3f0 drivers/gpu/drm/drm_file.c:438
__fput+0x44f/0xa60 fs/file_table.c:510
task_work_run+0x1d9/0x270 kernel/task_work.c:233
resume_user_mode_work include/linux/resume_user_mode.h:50 [inline]
__exit_to_user_mode_loop kernel/entry/common.c:67 [inline]
exit_to_user_mode_loop+0xed/0x480 kernel/entry/common.c:98
__exit_to_user_mode_prepare include/linux/irq-entry-common.h:226 [inline]
syscall_exit_to_user_mode_prepare include/linux/irq-entry-common.h:256 [inline]
syscall_exit_to_user_mode include/linux/entry-common.h:325 [inline]
do_syscall_64+0x33e/0xf80 arch/x86/entry/syscall_64.c:100
entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f736919c819
Code: ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 e8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007fffaf8d5118 EFLAGS: 00000246 ORIG_RAX: 00000000000001b4
RAX: 0000000000000000 RBX: 00007fffaf8d5200 RCX: 00007f736919c819
RDX: 0000000000000000 RSI: 000000000000001e RDI: 0000000000000003
RBP: 000000000001f76e R08: 0000000000000001 R09: 0000000000000000
R10: 0000001b32d20000 R11: 0000000000000246 R12: 00007fffaf8d5240
R13: 00007f736941609c R14: 000000000001f7f0 R15: 00007f7369416090
</TASK>

Allocated by task 6857:
kasan_save_stack mm/kasan/common.c:57 [inline]
kasan_save_track+0x3e/0x80 mm/kasan/common.c:78
poison_kmalloc_redzone mm/kasan/common.c:398 [inline]
__kasan_kmalloc+0x93/0xb0 mm/kasan/common.c:415
kasan_kmalloc include/linux/kasan.h:263 [inline]
__kmalloc_cache_noprof+0x31c/0x660 mm/slub.c:5380
kmalloc_noprof include/linux/slab.h:950 [inline]
kzalloc_noprof include/linux/slab.h:1188 [inline]
__drm_gem_shmem_create+0xc4/0x2e0 drivers/gpu/drm/drm_gem_shmem_helper.c:130
drm_gem_shmem_create drivers/gpu/drm/drm_gem_shmem_helper.c:157 [inline]
drm_gem_shmem_create_with_handle drivers/gpu/drm/drm_gem_shmem_helper.c:460 [inline]
drm_gem_shmem_dumb_create+0x72/0x120 drivers/gpu/drm/drm_gem_shmem_helper.c:549
drm_mode_create_dumb drivers/gpu/drm/drm_dumb_buffers.c:227 [inline]
drm_mode_create_dumb_ioctl+0x2bd/0x340 drivers/gpu/drm/drm_dumb_buffers.c:236
drm_ioctl_kernel+0x2df/0x3b0 drivers/gpu/drm/drm_ioctl.c:804
drm_ioctl+0x6ba/0xb80 drivers/gpu/drm/drm_ioctl.c:901
vfs_ioctl fs/ioctl.c:51 [inline]
__do_sys_ioctl fs/ioctl.c:597 [inline]
__se_sys_ioctl+0xfc/0x170 fs/ioctl.c:583
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0x15f/0xf80 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f

Freed by task 6864:
kasan_save_stack mm/kasan/common.c:57 [inline]
kasan_save_track+0x3e/0x80 mm/kasan/common.c:78
kasan_save_free_info+0x46/0x50 mm/kasan/generic.c:584
poison_slab_object mm/kasan/common.c:253 [inline]
__kasan_slab_free+0x5c/0x80 mm/kasan/common.c:285
kasan_slab_free include/linux/kasan.h:235 [inline]
slab_free_hook mm/slub.c:2685 [inline]
slab_free mm/slub.c:6165 [inline]
kfree+0x1c1/0x630 mm/slub.c:6483
drm_gem_handle_delete+0x90/0xb0 drivers/gpu/drm/drm_gem.c:432
drm_ioctl_kernel+0x2df/0x3b0 drivers/gpu/drm/drm_ioctl.c:804
drm_ioctl+0x6ba/0xb80 drivers/gpu/drm/drm_ioctl.c:901
vfs_ioctl fs/ioctl.c:51 [inline]
__do_sys_ioctl fs/ioctl.c:597 [inline]
__se_sys_ioctl+0xfc/0x170 fs/ioctl.c:583
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0x15f/0xf80 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f

The buggy address belongs to the object at ffff8880296c6800
which belongs to the cache kmalloc-1k of size 1024
The buggy address is located 648 bytes inside of
freed 1024-byte region [ffff8880296c6800, ffff8880296c6c00)

The buggy address belongs to the physical page:
page: refcount:0 mapcount:0 mapping:0000000000000000 index:0xffff8880296c1800 pfn:0x296c0
head: order:3 mapcount:0 entire_mapcount:0 nr_pages_mapped:0 pincount:0
flags: 0xfff00000000240(workingset|head|node=0|zone=1|lastcpupid=0x7ff)
page_type: f5(slab)
raw: 00fff00000000240 ffff88813fea7dc0 ffffea0001f5ea10 ffffea0000a31410
raw: ffff8880296c1800 000000080010000e 00000000f5000000 0000000000000000
head: 00fff00000000240 ffff88813fea7dc0 ffffea0001f5ea10 ffffea0000a31410
head: ffff8880296c1800 000000080010000e 00000000f5000000 0000000000000000
head: 00fff00000000003 ffffea0000a5b001 00000000ffffffff 00000000ffffffff
head: ffffffffffffffff 0000000000000000 00000000ffffffff 0000000000000008
page dumped because: kasan: bad access detected
page_owner tracks the page as allocated
page last allocated via order 3, migratetype Unmovable, gfp_mask 0xd2000(__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC), pid 619, tgid 619 (kworker/u8:7), ts 7851559667, free_ts 0
set_page_owner include/linux/page_owner.h:32 [inline]
post_alloc_hook+0x231/0x280 mm/page_alloc.c:1889
prep_new_page mm/page_alloc.c:1897 [inline]
get_page_from_freelist+0x24dc/0x2580 mm/page_alloc.c:3962
__alloc_frozen_pages_noprof+0x18d/0x380 mm/page_alloc.c:5250
alloc_slab_page mm/slub.c:3292 [inline]
allocate_slab+0x77/0x660 mm/slub.c:3481
new_slab mm/slub.c:3539 [inline]
refill_objects+0x331/0x3c0 mm/slub.c:7175
refill_sheaf mm/slub.c:2812 [inline]
__pcs_replace_empty_main+0x2e6/0x730 mm/slub.c:4615
alloc_from_pcs mm/slub.c:4717 [inline]
slab_alloc_node mm/slub.c:4851 [inline]
__kmalloc_cache_node_noprof+0x465/0x6b0 mm/slub.c:5388
kmalloc_node_noprof include/linux/slab.h:1077 [inline]
blk_mq_alloc_hctx block/blk-mq.c:4054 [inline]
blk_mq_alloc_and_init_hctx+0x17e/0xc50 block/blk-mq.c:4554
__blk_mq_realloc_hw_ctxs+0x2bd/0x670 block/blk-mq.c:4605
blk_mq_realloc_hw_ctxs block/blk-mq.c:4642 [inline]
blk_mq_init_allocated_queue+0x365/0x13e0 block/blk-mq.c:4672
blk_mq_alloc_queue+0x1ba/0x2e0 block/blk-mq.c:4454
scsi_alloc_sdev+0x7c0/0xc80 drivers/scsi/scsi_scan.c:339
scsi_probe_and_add_lun+0x200/0x4830 drivers/scsi/scsi_scan.c:1215
__scsi_scan_target+0x1f0/0xe10 drivers/scsi/scsi_scan.c:1786
scsi_scan_channel drivers/scsi/scsi_scan.c:1874 [inline]
scsi_scan_host_selected+0x372/0x690 drivers/scsi/scsi_scan.c:1903
do_scsi_scan_host drivers/scsi/scsi_scan.c:2042 [inline]
do_scan_async+0x124/0x760 drivers/scsi/scsi_scan.c:2052
page_owner free stack trace missing

Memory state around the buggy address:
ffff8880296c6980: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff8880296c6a00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff8880296c6a80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
^
ffff8880296c6b00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff8880296c6b80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================

Tested on:

commit: d60bc140 Merge tag 'pwrseq-updates-for-v7.1-rc1' of gi..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=142d04ce580000
kernel config: https://syzkaller.appspot.com/x/.config?x=85bd86f990609a1
dashboard link: https://syzkaller.appspot.com/bug?extid=b2e951687503f32f74ce
compiler: Debian clang version 21.1.8 (++20251221033036+2078da43e25a-1~exp1~20251221153213.50), Debian LLD 21.1.8
patch: https://syzkaller.appspot.com/x/patch.diff?x=1284b036580000