KASAN: slab-use-after-free Read in seq_printf

Status: moderation: reported on 2025/10/07 11:49
Subsystems: fs
Labels: prio:high
[Documentation on labels]
Reported-by: syzbot+3366add91c4b8d9822cf@syzkaller.appspotmail.com
First crash: 321d, last: 3h48m
▶ ▼ ✨ AI Jobs (4)
ID Workflow Result Correct Bug Created Started Finished Revision
3b0d2f4a assessment-security DenialOfService: ✅ Exploitable: ✅ FilesystemTrigger: ❌ NetworkTrigger: ❌ PeripheralTrigger: ❌ RemoteTrigger: ❌ Unprivileged: ✅ UserNamespace: ❌ VMGuestTrigger: ❌ VMHostTrigger: ❌ ❓ KASAN: slab-use-after-free Read in seq_printf 2026/05/25 12:01 2026/05/25 12:01 2026/05/25 12:55 c69befb3
4237d129 moderation Actionable: ✅ Confident: ✅ ❓ KASAN: slab-use-after-free Read in seq_printf 2026/02/06 12:22 2026/02/06 12:27 2026/02/06 12:35 97745f52
487d6af1 moderation 💥 KASAN: slab-use-after-free Read in seq_printf 2026/02/06 07:04 2026/02/06 09:45 2026/02/06 09:56 9b618abc
d54d6933 moderation Actionable: ✅ Confident: ✅ ❓ KASAN: slab-use-after-free Read in seq_printf 2026/01/15 18:55 2026/01/15 18:55 2026/01/15 19:24 a9d6a792
▶ ▼ Similar bugs (8)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
upstream KASAN: slab-out-of-bounds Read in seq_printf fs 19 5 466d 571d 0/29 auto-obsoleted due to no activity on 2025/08/09 17:54
upstream KMSAN: uninit-value in seq_printf (2) fs 7 syz, C 99 1527d 1794d 0/29 auto-closed as invalid on 2022/09/30 02:43
android-6-1 KASAN: slab-out-of-bounds Read in seq_printf (2) 17 1 138d 138d 0/2 auto-obsoleted due to no activity on 2026/07/03 17:29
android-5-10 KASAN: use-after-free Read in seq_printf 19 15 330d 438d 0/2 auto-obsoleted due to no activity on 2025/12/23 06:43
upstream KMSAN: kernel-infoleak in __skb_datagram_iter net 9 68 1059d 1164d 23/29 fixed on 2023/09/28 17:51
android-6-1 KASAN: slab-out-of-bounds Read in seq_printf 19 2 335d 339d 0/2 auto-obsoleted due to no activity on 2025/12/19 00:57
android-5-10 KASAN: use-after-free Read in seq_printf (2) 19 1 218d 218d 0/2 auto-obsoleted due to no activity on 2026/04/14 16:00
android-5-15 KASAN: use-after-free Read in seq_printf 19 1 336d 336d 0/2 auto-obsoleted due to no activity on 2025/12/17 23:30

Sample crash report:
loop1: detected capacity change from 0 to 256
==================================================================
BUG: KASAN: slab-use-after-free in string_nocheck lib/vsprintf.c:648 [inline]
BUG: KASAN: slab-use-after-free in string+0x216/0x2d0 lib/vsprintf.c:730
Read of size 1 at addr ffff888053398220 by task syz.1.642/8902

CPU: 0 UID: 0 PID: 8902 Comm: syz.1.642 Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 06/10/2026
Call Trace:
 <TASK>
 dump_stack_lvl+0xe8/0x150 lib/dump_stack.c:120
 print_address_description+0x55/0x1e0 mm/kasan/report.c:378
 print_report+0x58/0x70 mm/kasan/report.c:482
 kasan_report+0x117/0x150 mm/kasan/report.c:595
 string_nocheck lib/vsprintf.c:648 [inline]
 string+0x216/0x2d0 lib/vsprintf.c:730
 vsnprintf+0x74a/0xef0 lib/vsprintf.c:2945
 seq_vprintf fs/seq_file.c:392 [inline]
 seq_printf+0x188/0x290 fs/seq_file.c:407
 input_devices_seq_show+0x145/0x640 drivers/input/input.c:1116
 seq_read_iter+0x8d5/0xca0 fs/seq_file.c:273
 seq_read+0x367/0x480 fs/seq_file.c:163
 pde_read fs/proc/inode.c:308 [inline]
 proc_reg_read+0x1e9/0x2e0 fs/proc/inode.c:320
 vfs_read+0x213/0xa80 fs/read_write.c:572
 ksys_read+0x150/0x270 fs/read_write.c:716
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0x174/0x580 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7fed1859de59
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:00007fed19382028 EFLAGS: 00000246 ORIG_RAX: 0000000000000000
RAX: ffffffffffffffda RBX: 00007fed18825fa0 RCX: 00007fed1859de59
RDX: 0000000000002020 RSI: 0000200000003280 RDI: 0000000000000004
RBP: 00007fed18633e6f R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fed18826038 R14: 00007fed18825fa0 R15: 00007ffde861f708
 </TASK>

Allocated by task 8659:
 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]
 __do_kmalloc_node mm/slub.c:5362 [inline]
 __kmalloc_noprof+0x375/0x720 mm/slub.c:5387
 _kmalloc_noprof include/linux/slab.h:973 [inline]
 _kzalloc_noprof include/linux/slab.h:1290 [inline]
 ieee802_11_parse_elems_full+0x14b/0x2d60 net/mac80211/parse.c:1073
 ieee802_11_parse_elems net/mac80211/ieee80211_i.h:2551 [inline]
 ieee80211_inform_bss+0x163/0x10d0 net/mac80211/scan.c:79
 rdev_inform_bss net/wireless/rdev-ops.h:418 [inline]
 cfg80211_inform_single_bss_data+0xd9c/0x1be0 net/wireless/scan.c:2379
 cfg80211_inform_bss_data+0x258/0x3c40 net/wireless/scan.c:3238
 cfg80211_inform_bss_frame_data+0x3c7/0x730 net/wireless/scan.c:3329
 ieee80211_bss_info_update+0x791/0xa50 net/mac80211/scan.c:230
 ieee80211_scan_rx+0x552/0xa40 net/mac80211/scan.c:364
 __ieee80211_rx_handle_packet net/mac80211/rx.c:5395 [inline]
 ieee80211_rx_list+0x2b1d/0x3910 net/mac80211/rx.c:5688
 ieee80211_rx_napi+0x1ad/0x3d0 net/mac80211/rx.c:5711
 ieee80211_rx include/net/mac80211.h:5437 [inline]
 ieee80211_handle_queued_frames+0xe4/0x1d0 net/mac80211/main.c:452
 tasklet_action_common+0x2d7/0x490 kernel/softirq.c:938
 handle_softirqs+0x225/0x840 kernel/softirq.c:622
 __do_softirq kernel/softirq.c:656 [inline]
 invoke_softirq kernel/softirq.c:496 [inline]
 __irq_exit_rcu+0xca/0x220 kernel/softirq.c:735
 irq_exit_rcu+0x9/0x30 kernel/softirq.c:752
 instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1062 [inline]
 sysvec_apic_timer_interrupt+0xa6/0xc0 arch/x86/kernel/apic/apic.c:1062
 asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:674

Freed by task 8659:
 kasan_save_stack mm/kasan/common.c:57 [inline]
 kasan_save_track+0x3e/0x80 mm/kasan/common.c:78
 kasan_save_free_info+0x40/0x50 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:2705 [inline]
 slab_free mm/slub.c:6405 [inline]
 kfree+0x1c5/0x640 mm/slub.c:6720
 ieee80211_inform_bss+0xbda/0x10d0 net/mac80211/scan.c:164
 rdev_inform_bss net/wireless/rdev-ops.h:418 [inline]
 cfg80211_inform_single_bss_data+0xd9c/0x1be0 net/wireless/scan.c:2379
 cfg80211_inform_bss_data+0x258/0x3c40 net/wireless/scan.c:3238
 cfg80211_inform_bss_frame_data+0x3c7/0x730 net/wireless/scan.c:3329
 ieee80211_bss_info_update+0x791/0xa50 net/mac80211/scan.c:230
 ieee80211_scan_rx+0x552/0xa40 net/mac80211/scan.c:364
 __ieee80211_rx_handle_packet net/mac80211/rx.c:5395 [inline]
 ieee80211_rx_list+0x2b1d/0x3910 net/mac80211/rx.c:5688
 ieee80211_rx_napi+0x1ad/0x3d0 net/mac80211/rx.c:5711
 ieee80211_rx include/net/mac80211.h:5437 [inline]
 ieee80211_handle_queued_frames+0xe4/0x1d0 net/mac80211/main.c:452
 tasklet_action_common+0x2d7/0x490 kernel/softirq.c:938
 handle_softirqs+0x225/0x840 kernel/softirq.c:622
 __do_softirq kernel/softirq.c:656 [inline]
 invoke_softirq kernel/softirq.c:496 [inline]
 __irq_exit_rcu+0xca/0x220 kernel/softirq.c:735
 irq_exit_rcu+0x9/0x30 kernel/softirq.c:752
 instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1062 [inline]
 sysvec_apic_timer_interrupt+0xa6/0xc0 arch/x86/kernel/apic/apic.c:1062
 asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:674

The buggy address belongs to the object at ffff888053398000
 which belongs to the cache kmalloc-1k of size 1024
The buggy address is located 544 bytes inside of
 freed 1024-byte region [ffff888053398000, ffff888053398400)

The buggy address belongs to the physical page:
page: refcount:0 mapcount:0 mapping:0000000000000000 index:0xffff888053398000 pfn:0x53398
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 ffff88813fe3fdc0 ffffea0000a59810 ffffea0001e32e10
raw: ffff888053398000 000000080010000d 00000000f5000000 0000000000000000
head: 00fff00000000240 ffff88813fe3fdc0 ffffea0000a59810 ffffea0001e32e10
head: ffff888053398000 000000080010000d 00000000f5000000 0000000000000000
head: 00fff00000000003 fffffffffffffe01 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 0xd2820(GFP_ATOMIC|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC), pid 1102, tgid 1102 (kworker/u8:7), ts 90974115853, free_ts 24849158120
 set_page_owner include/linux/page_owner.h:32 [inline]
 post_alloc_hook+0x1f9/0x250 mm/page_alloc.c:1859
 prep_new_page mm/page_alloc.c:1867 [inline]
 get_page_from_freelist+0x21fa/0x2270 mm/page_alloc.c:3946
 __alloc_frozen_pages_noprof+0x18d/0x380 mm/page_alloc.c:5304
 alloc_slab_page mm/slub.c:3294 [inline]
 allocate_slab+0x79/0x5e0 mm/slub.c:3408
 new_slab mm/slub.c:3454 [inline]
 refill_objects+0x2d5/0x350 mm/slub.c:7338
 refill_sheaf mm/slub.c:2832 [inline]
 __pcs_replace_empty_main+0x2bf/0x6b0 mm/slub.c:4703
 alloc_from_pcs mm/slub.c:4801 [inline]
 slab_alloc_node mm/slub.c:4933 [inline]
 __do_kmalloc_node mm/slub.c:5361 [inline]
 __kmalloc_noprof+0x485/0x720 mm/slub.c:5387
 _kmalloc_noprof include/linux/slab.h:973 [inline]
 _kzalloc_noprof include/linux/slab.h:1290 [inline]
 neigh_alloc net/core/neighbour.c:518 [inline]
 ___neigh_create+0x6d2/0x22b0 net/core/neighbour.c:652
 ip6_finish_output2+0x6d6/0x13c0 net/ipv6/ip6_output.c:128
 NF_HOOK_COND include/linux/netfilter.h:307 [inline]
 ip6_output+0x337/0x540 net/ipv6/ip6_output.c:246
 dst_output include/net/dst.h:471 [inline]
 NF_HOOK include/linux/netfilter.h:318 [inline]
 ndisc_send_skb+0xcb2/0x1650 net/ipv6/ndisc.c:512
 ndisc_send_ns+0xd7/0x160 net/ipv6/ndisc.c:671
 addrconf_dad_work+0xa8d/0x15c0 net/ipv6/addrconf.c:4317
 process_one_work kernel/workqueue.c:3322 [inline]
 process_scheduled_works+0xa8e/0x14e0 kernel/workqueue.c:3405
 worker_thread+0xa47/0xfb0 kernel/workqueue.c:3486
 kthread+0x388/0x470 kernel/kthread.c:436
page last free pid 1 tgid 1 stack trace:
 reset_page_owner include/linux/page_owner.h:25 [inline]
 __free_pages_prepare mm/page_alloc.c:1406 [inline]
 free_pages_prepare+0x960/0xa60 mm/page_alloc.c:1451
 __free_contig_range_common+0x174/0x340 mm/page_alloc.c:6897
 destroy_args+0x4e5/0x570 mm/debug_vm_pgtable.c:993
 debug_vm_pgtable+0x3f8/0x410 mm/debug_vm_pgtable.c:1368
 do_one_initcall+0x250/0x870 init/main.c:1347
 do_initcall_level+0x10a/0x1a0 init/main.c:1409
 do_initcalls+0x59/0xa0 init/main.c:1425
 kernel_init_freeable+0x29d/0x3e0 init/main.c:1658
 kernel_init+0x1d/0x1d0 init/main.c:1548
 ret_from_fork+0x514/0xb70 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

Memory state around the buggy address:
 ffff888053398100: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff888053398180: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff888053398200: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                               ^
 ffff888053398280: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff888053398300: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================

Crashes (24):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/07/07 22:03 upstream 0e35b9b6ec0f 88a4b44c .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-root KASAN: slab-use-after-free Read in seq_printf
2026/05/30 22:13 upstream f5e5d3509bff 6b4a8443 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce KASAN: slab-use-after-free Read in seq_printf
2026/03/25 10:29 upstream bbeb83d3182a 35e4ff71 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce KASAN: slab-use-after-free Read in seq_printf
2026/01/08 06:25 upstream f0b9d8eb98df d6526ea3 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce KASAN: slab-use-after-free Read in seq_printf
2025/12/18 22:23 upstream ea1013c15392 d6526ea3 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-selinux-root KASAN: slab-use-after-free Read in seq_printf
2025/10/26 18:17 upstream 72761a7e3122 c0460fcd .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce KASAN: slab-use-after-free Read in seq_printf
2025/10/03 11:42 upstream e406d57be7bd 49379ee0 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce KASAN: slab-use-after-free Read in seq_printf
2026/01/01 10:13 upstream 9528d5c091c5 d6526ea3 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-386 KASAN: slab-use-after-free Read in seq_printf
2026/08/11 21:10 upstream f5bbbfec59b4 f8d35649 .config console log report info [disk image (non-bootable)] [vmlinux] [kernel image] ci-qemu-upstream KASAN: slab-use-after-free Read in seq_printf
2026/08/11 16:14 upstream f5bbbfec59b4 557a89d3 .config console log report info [disk image (non-bootable)] [vmlinux] [kernel image] ci-qemu-upstream KASAN: slab-use-after-free Read in seq_printf
2026/08/11 09:08 upstream d58772d8520c 557a89d3 .config console log report info [disk image (non-bootable)] [vmlinux] [kernel image] ci-qemu-upstream KASAN: slab-use-after-free Read in seq_printf
2026/08/11 09:08 upstream d58772d8520c 557a89d3 .config console log report info [disk image (non-bootable)] [vmlinux] [kernel image] ci-qemu-upstream KASAN: slab-use-after-free Read in seq_printf
2026/08/11 09:08 upstream d58772d8520c 557a89d3 .config console log report info [disk image (non-bootable)] [vmlinux] [kernel image] ci-qemu-upstream KASAN: slab-use-after-free Read in seq_printf
2026/08/06 22:40 upstream fcaeecb8b0cd c38879ea .config console log report info [disk image (non-bootable)] [vmlinux] [kernel image] ci-qemu-upstream KASAN: slab-use-after-free Read in seq_printf
2026/08/06 17:50 upstream fcaeecb8b0cd cc56899a .config console log report info [disk image (non-bootable)] [vmlinux] [kernel image] ci-qemu-upstream KASAN: slab-use-after-free Read in seq_printf
2026/08/21 02:16 upstream 9d2ed026f031 1e72964b .config console log report info [disk image (non-bootable)] [vmlinux] [kernel image] ci-qemu-upstream-386 KASAN: slab-use-after-free Read in seq_printf
2026/08/17 16:49 upstream 8d3ae59288f1 905244d6 .config console log report info [disk image (non-bootable)] [vmlinux] [kernel image] ci-qemu-upstream-386 KASAN: slab-use-after-free Read in seq_printf
2026/08/20 15:47 linux-next 7079a12d7506 1e72964b .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-rust-kasan-gce KASAN: slab-use-after-free Read in seq_printf
2026/08/20 15:45 linux-next 7079a12d7506 1e72964b .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-rust-kasan-gce KASAN: slab-use-after-free Read in seq_printf
2026/08/20 15:44 linux-next 7079a12d7506 1e72964b .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-rust-kasan-gce KASAN: slab-use-after-free Read in seq_printf
2026/08/19 14:03 linux-next 6a746cd265ae 1e72964b .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-rust-kasan-gce KASAN: slab-use-after-free Read in seq_printf
2026/08/19 14:02 linux-next 6a746cd265ae 1e72964b .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-rust-kasan-gce KASAN: slab-use-after-free Read in seq_printf
2026/08/19 01:21 linux-next 5453bc3279e9 1e72964b .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-rust-kasan-gce KASAN: slab-use-after-free Read in seq_printf
2026/08/20 15:47 linux-next 7079a12d7506 1e72964b .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-rust-kasan-gce KASAN: slab-out-of-bounds Read in seq_printf
* Struck through repros no longer work on HEAD.