syzbot


KASAN: use-after-free Write in enqueue_timer (2)

Status: premoderation: reported on 2025/11/01 08:53
Reported-by: syzbot+c986a0ea1d1af31b3004@syzkaller.appspotmail.com
First crash: 71d, last: 3d20h
Similar bugs (8)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
android-54 KASAN: use-after-free Write in enqueue_timer (2) 24 C 5369 230d 328d 0/2 upstream: reported C repro on 2025/02/17 15:17
android-54 KASAN: use-after-free Write in enqueue_timer 24 C 4288 557d 1064d 0/2 auto-obsoleted due to no activity on 2024/09/11 16:22
upstream KASAN: use-after-free Write in enqueue_timer net 24 1 1154d 1154d 22/29 fixed on 2023/02/24 13:50
android-5-15 KASAN: use-after-free Write in enqueue_timer 24 1 724d 724d 0/2 auto-obsoleted due to no activity on 2024/04/17 12:01
android-6-1 KASAN: use-after-free Write in enqueue_timer origin:lts 24 C 339 5h12m 535d 0/2 upstream: reported C repro on 2024/07/25 13:16
upstream KASAN: slab-use-after-free Write in enqueue_timer net 24 18 972d 987d 0/29 auto-obsoleted due to no activity on 2023/08/22 15:17
upstream KASAN: slab-out-of-bounds Write in enqueue_timer bluetooth 23 1 207d 203d 0/29 auto-obsoleted due to no activity on 2025/09/26 09:41
upstream KASAN: invalid-access Write in enqueue_timer ext4 -1 20 1769d 1791d 0/29 auto-closed as invalid on 2021/07/08 00:48

Sample crash report:
EXT4-fs error (device loop3): ext4_read_inline_dir:1622: inode #12: block 7: comm syz.3.2275: path /6/file1/file0: bad entry in directory: inode out of bounds - offset=24, inode=150994957, rec_len=16, size=80 fake=0
==================================================================
BUG: KASAN: use-after-free in hlist_add_head include/linux/list.h:902 [inline]
BUG: KASAN: use-after-free in enqueue_timer+0xae/0x480 kernel/time/timer.c:588
Write of size 8 at addr ffff88814939c4c0 by task syz.3.2275/9575

CPU: 0 PID: 9575 Comm: syz.3.2275 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025
Call Trace:
 <TASK>
 __dump_stack+0x21/0x30 lib/dump_stack.c:88
 dump_stack_lvl+0xee/0x150 lib/dump_stack.c:106
 print_address_description+0x7f/0x2c0 mm/kasan/report.c:248
 __kasan_report mm/kasan/report.c:427 [inline]
 kasan_report+0xf1/0x140 mm/kasan/report.c:444
 __asan_report_store8_noabort+0x17/0x20 mm/kasan/report_generic.c:314
 hlist_add_head include/linux/list.h:902 [inline]
 enqueue_timer+0xae/0x480 kernel/time/timer.c:588
 __mod_timer+0x79f/0xb30 kernel/time/timer.c:-1
 mod_timer+0x1f/0x30 kernel/time/timer.c:1119
 ext4_update_super+0x9e6/0xde0 fs/ext4/super.c:5474
 ext4_commit_super+0x1f0/0x450 fs/ext4/super.c:5494
 ext4_handle_error+0x541/0x7b0 fs/ext4/super.c:658
 __ext4_error_file+0x295/0x570 fs/ext4/super.c:825
 __ext4_check_dir_entry+0x763/0x970 fs/ext4/dir.c:114
 ext4_read_inline_dir+0x887/0xd90 fs/ext4/inline.c:1621
 ext4_readdir+0x383/0x3a40 fs/ext4/dir.c:161
 iterate_dir+0x260/0x600 fs/readdir.c:-1
 __do_sys_getdents64 fs/readdir.c:369 [inline]
 __se_sys_getdents64+0xe5/0x240 fs/readdir.c:354
 __x64_sys_getdents64+0x7b/0x90 fs/readdir.c:354
 x64_sys_call+0x592/0x9a0 arch/x86/include/generated/asm/syscalls_64.h:218
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x66/0xd0
RIP: 0033:0x7f68f7401749
Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 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 a8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f68f5e27038 EFLAGS: 00000246 ORIG_RAX: 00000000000000d9
RAX: ffffffffffffffda RBX: 00007f68f7658180 RCX: 00007f68f7401749
RDX: 00000000000000e0 RSI: 0000200000000fc0 RDI: 000000000000000c
RBP: 00007f68f7485f91 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f68f7658218 R14: 00007f68f7658180 R15: 00007ffd7508a948
 </TASK>

Allocated by task 6546:
 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:433 [inline]
 ____kasan_kmalloc mm/kasan/common.c:512 [inline]
 __kasan_kmalloc+0xda/0x110 mm/kasan/common.c:521
 kasan_kmalloc include/linux/kasan.h:227 [inline]
 kmem_cache_alloc_trace+0x119/0x270 mm/slub.c:3274
 kmalloc include/linux/slab.h:619 [inline]
 kzalloc include/linux/slab.h:750 [inline]
 ext4_fill_super+0xc5/0x9090 fs/ext4/super.c:3888
 mount_bdev+0x2ae/0x3e0 fs/super.c:1400
 ext4_mount+0x34/0x40 fs/ext4/super.c:6623
 legacy_get_tree+0xed/0x190 fs/fs_context.c:611
 vfs_get_tree+0x89/0x260 fs/super.c:1530
 do_new_mount+0x25a/0xa20 fs/namespace.c:3034
 path_mount+0x675/0x1020 fs/namespace.c:3364
 do_mount fs/namespace.c:3377 [inline]
 __do_sys_mount fs/namespace.c:3585 [inline]
 __se_sys_mount+0x318/0x380 fs/namespace.c:3562
 __x64_sys_mount+0xbf/0xd0 fs/namespace.c:3562
 x64_sys_call+0x6bf/0x9a0 arch/x86/include/generated/asm/syscalls_64.h:166
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x66/0xd0

Freed by task 7285:
 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:365
 __kasan_slab_free+0x11/0x20 mm/kasan/common.c:373
 kasan_slab_free include/linux/kasan.h:193 [inline]
 slab_free_hook mm/slub.c:1728 [inline]
 slab_free_freelist_hook+0xc2/0x190 mm/slub.c:1754
 slab_free mm/slub.c:3526 [inline]
 kfree+0xc4/0x270 mm/slub.c:4588
 ext4_put_super+0x969/0xa70 fs/ext4/super.c:1277
 generic_shutdown_super+0x151/0x330 fs/super.c:475
 kill_block_super+0x7f/0xf0 fs/super.c:1427
 deactivate_locked_super+0xa0/0x100 fs/super.c:335
 deactivate_super+0xaf/0xe0 fs/super.c:366
 cleanup_mnt+0x446/0x500 fs/namespace.c:1148
 __cleanup_mnt+0x19/0x20 fs/namespace.c:1155
 task_work_run+0x127/0x190 kernel/task_work.c:188
 exit_task_work include/linux/task_work.h:33 [inline]
 do_exit+0xa7e/0x27a0 kernel/exit.c:889
 do_group_exit+0x141/0x310 kernel/exit.c:1003
 get_signal+0x66a/0x1480 kernel/signal.c:2907
 arch_do_signal_or_restart+0xc1/0x10f0 arch/x86/kernel/signal.c:867
 handle_signal_work kernel/entry/common.c:154 [inline]
 exit_to_user_mode_loop+0xa7/0xe0 kernel/entry/common.c:178
 exit_to_user_mode_prepare+0x87/0xd0 kernel/entry/common.c:214
 __syscall_exit_to_user_mode_work kernel/entry/common.c:296 [inline]
 syscall_exit_to_user_mode+0x1a/0x30 kernel/entry/common.c:307
 do_syscall_64+0x58/0xa0 arch/x86/entry/common.c:86
 entry_SYSCALL_64_after_hwframe+0x66/0xd0

The buggy address belongs to the object at ffff88814939c000
 which belongs to the cache kmalloc-4k of size 4096
The buggy address is located 1216 bytes inside of
 4096-byte region [ffff88814939c000, ffff88814939d000)
The buggy address belongs to the page:
page:ffffea000524e600 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x149398
head:ffffea000524e600 order:3 compound_mapcount:0 compound_pincount:0
flags: 0x4000000000010200(slab|head|zone=1)
raw: 4000000000010200 0000000000000000 0000000300000001 ffff888100043380
raw: 0000000000000000 0000000000040004 00000001ffffffff 0000000000000000
page dumped because: kasan: bad access detected
page_owner tracks the page as allocated
page last allocated via order 3, migratetype Unmovable, gfp_mask 0x1d20c0(__GFP_IO|__GFP_FS|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC|__GFP_HARDWALL), pid 5965, ts 270968443314, free_ts 269448988927
 set_page_owner include/linux/page_owner.h:33 [inline]
 post_alloc_hook+0x192/0x1b0 mm/page_alloc.c:2605
 prep_new_page+0x1c/0x110 mm/page_alloc.c:2611
 get_page_from_freelist+0x2cc5/0x2d50 mm/page_alloc.c:4485
 __alloc_pages+0x18f/0x440 mm/page_alloc.c:5808
 alloc_slab_page mm/slub.c:-1 [inline]
 allocate_slab mm/slub.c:1937 [inline]
 new_slab+0xa1/0x4d0 mm/slub.c:2000
 ___slab_alloc+0x381/0x810 mm/slub.c:3033
 __slab_alloc+0x49/0x90 mm/slub.c:3120
 slab_alloc_node mm/slub.c:3211 [inline]
 slab_alloc mm/slub.c:3255 [inline]
 kmem_cache_alloc_trace+0x146/0x270 mm/slub.c:3272
 kmalloc include/linux/slab.h:619 [inline]
 kzalloc include/linux/slab.h:750 [inline]
 kobject_uevent_env+0x272/0x700 lib/kobject_uevent.c:539
 kobject_uevent+0x1d/0x30 lib/kobject_uevent.c:657
 __kobject_del+0xd7/0x2f0 lib/kobject.c:625
 kobject_cleanup lib/kobject.c:704 [inline]
 kobject_release lib/kobject.c:744 [inline]
 kref_put include/linux/kref.h:65 [inline]
 kobject_put+0x1db/0x270 lib/kobject.c:761
 netdev_queue_update_kobjects+0x37b/0x3e0 net/core/net-sysfs.c:1726
 netif_set_real_num_tx_queues+0x160/0x780 net/core/dev.c:2979
 veth_init_queues drivers/net/veth.c:1608 [inline]
 veth_newlink+0x9bc/0xda0 drivers/net/veth.c:1726
 __rtnl_newlink net/core/rtnetlink.c:3524 [inline]
 rtnl_newlink+0x112d/0x17b0 net/core/rtnetlink.c:3572
page last free stack trace:
 reset_page_owner include/linux/page_owner.h:26 [inline]
 free_pages_prepare mm/page_alloc.c:1472 [inline]
 free_pcp_prepare mm/page_alloc.c:1544 [inline]
 free_unref_page_prepare+0x542/0x550 mm/page_alloc.c:3534
 free_unref_page+0xa2/0x550 mm/page_alloc.c:3616
 free_the_page mm/page_alloc.c:805 [inline]
 __free_pages+0x6c/0x100 mm/page_alloc.c:5884
 __free_slab+0xe8/0x1e0 mm/slub.c:2025
 free_slab mm/slub.c:2040 [inline]
 discard_slab mm/slub.c:2046 [inline]
 __unfreeze_partials+0x160/0x190 mm/slub.c:2532
 put_cpu_partial+0xc6/0x120 mm/slub.c:2612
 __slab_free+0x1d4/0x290 mm/slub.c:3395
 do_slab_free mm/slub.c:3514 [inline]
 ___cache_free+0x104/0x120 mm/slub.c:3535
 qlink_free+0x4d/0x90 mm/kasan/quarantine.c:157
 qlist_free_all+0x5f/0xb0 mm/kasan/quarantine.c:176
 kasan_quarantine_reduce+0x14a/0x170 mm/kasan/quarantine.c:283
 __kasan_slab_alloc+0x2f/0xf0 mm/kasan/common.c:443
 kasan_slab_alloc include/linux/kasan.h:217 [inline]
 slab_post_alloc_hook+0x4f/0x2b0 mm/slab.h:550
 slab_alloc_node mm/slub.c:3245 [inline]
 slab_alloc mm/slub.c:3255 [inline]
 kmem_cache_alloc+0xf7/0x260 mm/slub.c:3260
 kmem_cache_alloc_node include/linux/slab.h:492 [inline]
 __alloc_skb+0xe0/0x740 net/core/skbuff.c:416
 alloc_skb_fclone include/linux/skbuff.h:1233 [inline]
 sk_stream_alloc_skb+0x21a/0xb60 net/ipv4/tcp.c:889

Memory state around the buggy address:
 ffff88814939c380: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff88814939c400: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff88814939c480: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                                           ^
 ffff88814939c500: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff88814939c580: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================

Crashes (2):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/01/08 11:06 android13-5.15-lts 050dc55b0457 d6526ea3 .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-5-15 KASAN: use-after-free Write in enqueue_timer
2025/11/01 08:52 android13-5.15-lts 1edb21e89ce4 2c50b6a9 .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-5-15 KASAN: use-after-free Write in enqueue_timer
* Struck through repros no longer work on HEAD.