KASAN: use-after-free Read in worker_thread (2)

Status: upstream: reported C repro on 2026/11/06 13:13
Reported-by: syzbot+f11752b2c94491a79069@syzkaller.appspotmail.com
First crash: 2d16h, last: 2d15h
▶ ▼ Similar bugs (8)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
android-5-10 KASAN: use-after-free Read in worker_thread 19 1 819d 819d 0/2 auto-obsoleted due to no activity on 2024/11/09 22:41
android-5-15 KASAN: use-after-free Read in worker_thread missing-backport 19 syz, C unreliable error 178 327d 1484d 0/2 auto-obsoleted due to no activity on 2026/03/17 00:54
upstream KASAN: use-after-free Read in worker_thread (2) net 19 syz 6 3278d 3287d 5/29 fixed on 2018/04/06 16:37
upstream KASAN: use-after-free Read in worker_thread 19 2 3342d 3299d 0/29 closed as invalid on 2017/10/27 09:33
android-6-1 KASAN: use-after-free Read in worker_thread missing-backport 19 syz, C error error 171 289d 1243d 0/2 auto-obsoleted due to no activity on 2026/04/14 06:09
upstream general protection fault in worker_thread kernel 2 1 1499d 1495d 0/29 auto-obsoleted due to no activity on 2022/12/30 10:32
upstream KMSAN: uninit-value in worker_thread (3) ext4 7 2 1864d 1947d 0/29 auto-closed as invalid on 2021/12/30 14:37
upstream general protection fault in worker_thread (2) io-uring 2 syz 1 1236d 1232d 0/29 auto-obsoleted due to no activity on 2023/09/29 13:47

Sample crash report:
==================================================================
BUG: KASAN: use-after-free in worker_thread+0xa63/0x13c0 kernel/workqueue.c:2445
Read of size 8 at addr ffff88811f8539e0 by task kworker/0:1/15

CPU: 0 PID: 15 Comm: kworker/0:1 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/15/2026
Workqueue:  0x0 (kdmflush)
Call Trace:
 __dump_stack+0x21/0x24 lib/dump_stack.c:77
 dump_stack_lvl+0x1a7/0x208 lib/dump_stack.c:118
 print_address_description+0x7f/0x2c0 mm/kasan/report.c:248
 __kasan_report mm/kasan/report.c:435 [inline]
 kasan_report+0x100/0x140 mm/kasan/report.c:452
 __asan_report_load8_noabort+0x14/0x20 mm/kasan/report_generic.c:309
 worker_thread+0xa63/0x13c0 kernel/workqueue.c:2445
 kthread+0x324/0x3b0 kernel/kthread.c:313
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:298

Allocated by task 298:
 kasan_save_stack mm/kasan/common.c:38 [inline]
 kasan_set_track mm/kasan/common.c:45 [inline]
 set_alloc_info mm/kasan/common.c:430 [inline]
 __kasan_slab_alloc+0xb7/0xe0 mm/kasan/common.c:463
 kasan_slab_alloc include/linux/kasan.h:244 [inline]
 slab_post_alloc_hook+0x5d/0x2f0 mm/slab.h:580
 slab_alloc_node mm/slub.c:2952 [inline]
 slab_alloc mm/slub.c:2960 [inline]
 kmem_cache_alloc+0x15a/0x2d0 mm/slub.c:2965
 mempool_alloc_slab+0x1d/0x30 mm/mempool.c:513
 mempool_alloc+0x128/0x490 mm/mempool.c:393
 bio_alloc_bioset+0x196/0x570 block/bio.c:486
 alloc_io drivers/md/dm.c:590 [inline]
 init_clone_info drivers/md/dm.c:1578 [inline]
 __split_and_process_bio drivers/md/dm.c:1595 [inline]
 dm_submit_bio+0x200/0x1160 drivers/md/dm.c:1680
 __submit_bio block/blk-core.c:927 [inline]
 __submit_bio_noacct block/blk-core.c:975 [inline]
 submit_bio_noacct+0x466/0xe50 block/blk-core.c:1054
 submit_bio+0x342/0x710 block/blk-core.c:1123
 submit_bh_wbc+0x5f8/0x6e0 fs/buffer.c:3085
 submit_bh fs/buffer.c:3091 [inline]
 ll_rw_block+0x1ed/0x250 fs/buffer.c:-1
 __block_write_begin_int+0x76d/0x15a0 fs/buffer.c:2072
 __block_write_begin fs/buffer.c:2092 [inline]
 block_write_begin+0x54/0xd0 fs/buffer.c:2151
 blkdev_write_begin+0x3c/0x50 fs/block_dev.c:660
 generic_perform_write+0x2ce/0x540 mm/filemap.c:3509
 __generic_file_write_iter+0x24b/0x480 mm/filemap.c:3638
 blkdev_write_iter+0x2f2/0x3f0 fs/block_dev.c:1929
 call_write_iter include/linux/fs.h:2072 [inline]
 new_sync_write fs/read_write.c:518 [inline]
 vfs_write+0x770/0xd70 fs/read_write.c:605
 ksys_pwrite64 fs/read_write.c:712 [inline]
 __do_sys_pwrite64 fs/read_write.c:722 [inline]
 __se_sys_pwrite64 fs/read_write.c:719 [inline]
 __x64_sys_pwrite64+0x194/0x220 fs/read_write.c:719
 do_syscall_64+0x31/0x40 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x61/0xcb

Freed by task 298:
 kasan_save_stack mm/kasan/common.c:38 [inline]
 kasan_set_track+0x4a/0x70 mm/kasan/common.c:45
 kasan_set_free_info+0x23/0x40 mm/kasan/generic.c:370
 ____kasan_slab_free+0x125/0x160 mm/kasan/common.c:362
 __kasan_slab_free+0x11/0x20 mm/kasan/common.c:370
 kasan_slab_free include/linux/kasan.h:220 [inline]
 slab_free_hook mm/slub.c:1600 [inline]
 slab_free_freelist_hook+0xc5/0x190 mm/slub.c:1626
 slab_free mm/slub.c:3208 [inline]
 kmem_cache_free+0x100/0x2d0 mm/slub.c:3224
 mempool_free_slab+0x1d/0x30 mm/mempool.c:520
 mempool_free+0xd5/0x330 mm/mempool.c:502
 bio_free+0x25c/0x360 block/bio.c:266
 bio_put+0xbf/0x110 block/bio.c:-1
 free_io drivers/md/dm.c:613 [inline]
 dm_io_dec_pending+0x353/0x990 drivers/md/dm.c:892
 __split_and_process_bio drivers/md/dm.c:1643 [inline]
 dm_submit_bio+0x8db/0x1160 drivers/md/dm.c:1680
 __submit_bio block/blk-core.c:927 [inline]
 __submit_bio_noacct block/blk-core.c:975 [inline]
 submit_bio_noacct+0x466/0xe50 block/blk-core.c:1054
 submit_bio+0x342/0x710 block/blk-core.c:1123
 submit_bh_wbc+0x5f8/0x6e0 fs/buffer.c:3085
 submit_bh fs/buffer.c:3091 [inline]
 ll_rw_block+0x1ed/0x250 fs/buffer.c:-1
 __block_write_begin_int+0x76d/0x15a0 fs/buffer.c:2072
 __block_write_begin fs/buffer.c:2092 [inline]
 block_write_begin+0x54/0xd0 fs/buffer.c:2151
 blkdev_write_begin+0x3c/0x50 fs/block_dev.c:660
 generic_perform_write+0x2ce/0x540 mm/filemap.c:3509
 __generic_file_write_iter+0x24b/0x480 mm/filemap.c:3638
 blkdev_write_iter+0x2f2/0x3f0 fs/block_dev.c:1929
 call_write_iter include/linux/fs.h:2072 [inline]
 new_sync_write fs/read_write.c:518 [inline]
 vfs_write+0x770/0xd70 fs/read_write.c:605
 ksys_pwrite64 fs/read_write.c:712 [inline]
 __do_sys_pwrite64 fs/read_write.c:722 [inline]
 __se_sys_pwrite64 fs/read_write.c:719 [inline]
 __x64_sys_pwrite64+0x194/0x220 fs/read_write.c:719
 do_syscall_64+0x31/0x40 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x61/0xcb

Last potentially related work creation:
 kasan_save_stack+0x3a/0x60 mm/kasan/common.c:38
 __kasan_record_aux_stack+0xd2/0x100 mm/kasan/generic.c:348
 kasan_record_aux_stack_noalloc+0xb/0x10 mm/kasan/generic.c:358
 insert_work+0x51/0x320 kernel/workqueue.c:1352
 __queue_work+0x91f/0xca0 kernel/workqueue.c:1518
 queue_work_on+0xe6/0x140 kernel/workqueue.c:1545
 queue_work include/linux/workqueue.h:515 [inline]
 kcryptd_queue_read drivers/md/dm-crypt.c:1882 [inline]
 crypt_map+0x5ea/0xc90 drivers/md/dm-crypt.c:3403
 __map_bio+0x133/0x7a0 drivers/md/dm.c:1279
 __clone_and_map_data_bio drivers/md/dm.c:1473 [inline]
 __split_and_process_non_flush+0x71f/0x9a0 drivers/md/dm.c:1564
 __split_and_process_bio drivers/md/dm.c:1608 [inline]
 dm_submit_bio+0x7f4/0x1160 drivers/md/dm.c:1680
 __submit_bio block/blk-core.c:927 [inline]
 __submit_bio_noacct block/blk-core.c:975 [inline]
 submit_bio_noacct+0x466/0xe50 block/blk-core.c:1054
 submit_bio+0x342/0x710 block/blk-core.c:1123
 submit_bh_wbc+0x5f8/0x6e0 fs/buffer.c:3085
 submit_bh fs/buffer.c:3091 [inline]
 ll_rw_block+0x1ed/0x250 fs/buffer.c:-1
 __block_write_begin_int+0x76d/0x15a0 fs/buffer.c:2072
 __block_write_begin fs/buffer.c:2092 [inline]
 block_write_begin+0x54/0xd0 fs/buffer.c:2151
 blkdev_write_begin+0x3c/0x50 fs/block_dev.c:660
 generic_perform_write+0x2ce/0x540 mm/filemap.c:3509
 __generic_file_write_iter+0x24b/0x480 mm/filemap.c:3638
 blkdev_write_iter+0x2f2/0x3f0 fs/block_dev.c:1929
 call_write_iter include/linux/fs.h:2072 [inline]
 new_sync_write fs/read_write.c:518 [inline]
 vfs_write+0x770/0xd70 fs/read_write.c:605
 ksys_pwrite64 fs/read_write.c:712 [inline]
 __do_sys_pwrite64 fs/read_write.c:722 [inline]
 __se_sys_pwrite64 fs/read_write.c:719 [inline]
 __x64_sys_pwrite64+0x194/0x220 fs/read_write.c:719
 do_syscall_64+0x31/0x40 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x61/0xcb

The buggy address belongs to the object at ffff88811f8539c0
 which belongs to the cache bio-3 of size 1176
The buggy address is located 32 bytes inside of
 1176-byte region [ffff88811f8539c0, ffff88811f853e58)
The buggy address belongs to the page:
page:ffffea00047e1400 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x11f850
head:ffffea00047e1400 order:2 compound_mapcount:0 compound_pincount:0
flags: 0x4000000000010200(slab|head)
raw: 4000000000010200 dead000000000100 dead000000000122 ffff88810c396900
raw: 0000000000000000 00000000800c000c 00000001ffffffff 0000000000000000
page dumped because: kasan: bad access detected
page_owner tracks the page as allocated
page last allocated via order 2, migratetype Unmovable, gfp_mask 0xd20c0(__GFP_IO|__GFP_FS|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC), pid 298, ts 33645595872, free_ts 0
 set_page_owner include/linux/page_owner.h:35 [inline]
 post_alloc_hook mm/page_alloc.c:2456 [inline]
 prep_new_page+0x176/0x190 mm/page_alloc.c:2462
 get_page_from_freelist+0x225f/0x23f0 mm/page_alloc.c:4254
 __alloc_pages_nodemask+0x29a/0x640 mm/page_alloc.c:5384
 alloc_slab_page mm/slub.c:-1 [inline]
 allocate_slab mm/slub.c:1813 [inline]
 new_slab+0x84/0x3f0 mm/slub.c:1874
 new_slab_objects mm/slub.c:2632 [inline]
 ___slab_alloc+0x2f8/0x4c0 mm/slub.c:2796
 __slab_alloc+0x63/0xa0 mm/slub.c:2836
 slab_alloc_node mm/slub.c:2918 [inline]
 slab_alloc mm/slub.c:2960 [inline]
 kmem_cache_alloc+0x1a4/0x2d0 mm/slub.c:2965
 mempool_alloc_slab+0x1d/0x30 mm/mempool.c:513
 mempool_init_node+0x1e3/0x4a0 mm/mempool.c:202
 mempool_init+0x3c/0x50 mm/mempool.c:231
 mempool_init_slab_pool include/linux/mempool.h:62 [inline]
 bioset_init+0x418/0x5f0 block/bio.c:1602
 bioset_init_from_src+0xb3/0x120 block/bio.c:1637
 __bind_mempools drivers/md/dm.c:1964 [inline]
 __bind drivers/md/dm.c:2038 [inline]
 dm_swap_table+0x442/0x600 drivers/md/dm.c:2421
 do_resume drivers/md/dm-ioctl.c:1088 [inline]
 dev_suspend+0x13e/0x5d0 drivers/md/dm-ioctl.c:1131
 ctl_ioctl drivers/md/dm-ioctl.c:1925 [inline]
 dm_ctl_ioctl+0x8ee/0xca0 drivers/md/dm-ioctl.c:1947
 vfs_ioctl fs/ioctl.c:48 [inline]
 __do_sys_ioctl fs/ioctl.c:753 [inline]
 __se_sys_ioctl+0x121/0x1a0 fs/ioctl.c:739
page_owner free stack trace missing

Memory state around the buggy address:
 ffff88811f853880: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff88811f853900: fb fb fb fc fc fc fc fc fc fc fc fc fc fc fc fc
>ffff88811f853980: fc fc fc fc fc fc fc fc fa fb fb fb fb fb fb fb
                                                       ^
 ffff88811f853a00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff88811f853a80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================
BUG: kernel NULL pointer dereference, address: 0000000000000000
#PF: supervisor instruction fetch in kernel mode
#PF: error_code(0x0010) - not-present page
PGD 0 P4D 0 
Oops: 0010 [#1] PREEMPT SMP KASAN
CPU: 0 PID: 15 Comm: kworker/0:1 Tainted: G    B             syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/15/2026
Workqueue: kcryptd_io/253:0 kcryptd_io_read_work
RIP: 0010:0x0
Code: Unable to access opcode bytes at RIP 0xffffffffffffffd6.
RSP: 0018:ffffc900000f7a78 EFLAGS: 00010282
RAX: 0000000000000000 RBX: dffffc0000000000 RCX: ffffffff81886bdf
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000092800
RBP: ffffc900000f7bd8 R08: ffffc900000f7b47 R09: ffffc900000f7b20
R10: dffffc0000000000 R11: fffff5200001ef69 R12: 0000000000092800
R13: 1ffff11023df73f6 R14: 0000000000000000 R15: ffff88811efb9fb0
FS:  0000000000000000(0000) GS:ffff8881f7000000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: ffffffffffffffd6 CR3: 000000000640f000 CR4: 00000000003506b0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 mempool_alloc+0x128/0x490 mm/mempool.c:393
 bio_alloc_bioset+0x196/0x570 block/bio.c:486
 bio_clone_fast+0x28/0x240 block/bio.c:711
 kcryptd_io_read+0x78/0x4e0 drivers/md/dm-crypt.c:1848
 kcryptd_io_read_work+0x3b/0xa0 drivers/md/dm-crypt.c:1872
 process_one_work+0x6fd/0xbc0 kernel/workqueue.c:2301
 worker_thread+0xa8e/0x13c0 kernel/workqueue.c:2447
 kthread+0x324/0x3b0 kernel/kthread.c:313
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:298
Modules linked in:
CR2: 0000000000000000
---[ end trace 98ebebe9a7ac5b86 ]---
RIP: 0010:0x0
Code: Unable to access opcode bytes at RIP 0xffffffffffffffd6.
RSP: 0018:ffffc900000f7a78 EFLAGS: 00010282
RAX: 0000000000000000 RBX: dffffc0000000000 RCX: ffffffff81886bdf
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000092800
RBP: ffffc900000f7bd8 R08: ffffc900000f7b47 R09: ffffc900000f7b20
R10: dffffc0000000000 R11: fffff5200001ef69 R12: 0000000000092800
R13: 1ffff11023df73f6 R14: 0000000000000000 R15: ffff88811efb9fb0
FS:  0000000000000000(0000) GS:ffff8881f7000000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: ffffffffffffffd6 CR3: 000000000640f000 CR4: 00000000003506b0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400

Crashes (3):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/11/06 13:57 android13-5.10-lts f61a392235e0 5cecaf1f .config strace log report syz / log C [disk image] [vmlinux] [kernel image] ci2-android-5-10 KASAN: use-after-free Read in worker_thread
2026/11/06 13:10 android13-5.10-lts f61a392235e0 5cecaf1f .config strace log report syz / log C [disk image] [vmlinux] [kernel image] ci2-android-5-10 KASAN: use-after-free Read in worker_thread
2026/11/06 12:48 android13-5.10-lts f61a392235e0 5cecaf1f .config strace log report syz / log [disk image] [vmlinux] [kernel image] ci2-android-5-10 KASAN: use-after-free Read in worker_thread
* Struck through repros no longer work on HEAD.