KASAN: use-after-free Read in seq_printf (3)

Status: premoderation: reported on 2026/08/30 00:45
Reported-by: syzbot+f36aa1df8927979e175e@syzkaller.appspotmail.com
First crash: 20d, last: 8d02h
▶ ▼ Similar bugs (11)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
android-5-15 KASAN: use-after-free Read in seq_printf (2) 19 3 1d05h 24d 0/2 premoderation: reported on 2026/08/26 02:30
android-5-10 KASAN: use-after-free Read in seq_printf 19 15 360d 467d 0/2 auto-obsoleted due to no activity on 2025/12/23 06:43
upstream KASAN: slab-out-of-bounds Read in seq_printf fs 19 5 496d 601d 0/29 auto-obsoleted due to no activity on 2025/08/09 17:54
android-6-1 KASAN: slab-out-of-bounds Read in seq_printf 19 2 364d 369d 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 248d 248d 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 365d 365d 0/2 auto-obsoleted due to no activity on 2025/12/17 23:30
upstream KMSAN: uninit-value in seq_printf (2) fs 7 syz, C 99 1557d 1823d 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 168d 168d 0/2 auto-obsoleted due to no activity on 2026/07/03 17:29
upstream KMSAN: kernel-infoleak in __skb_datagram_iter net 9 68 1089d 1194d 23/29 fixed on 2023/09/28 17:51
upstream KASAN: slab-use-after-free Read in seq_printf prio:high fs 19 53 3h27m 18h46m 0/29 upstream: reported on 2026/09/19 02:15
linux-6.6 KASAN: slab-use-after-free Read in seq_printf 19 1 25d 25d 0/2 upstream: reported on 2026/08/25 13:48

Sample crash report:
==================================================================
BUG: KASAN: use-after-free in string_nocheck lib/vsprintf.c:641 [inline]
BUG: KASAN: use-after-free in string+0x20f/0x2a0 lib/vsprintf.c:723
Read of size 1 at addr ffff88812725dd78 by task syz.2.647/2974

CPU: 1 PID: 2974 Comm: syz.2.647 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/24/2026
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_load1_noabort+0x14/0x20 mm/kasan/report_generic.c:306
 string_nocheck lib/vsprintf.c:641 [inline]
 string+0x20f/0x2a0 lib/vsprintf.c:723
 vsnprintf+0xec5/0x1990 lib/vsprintf.c:2689
 seq_vprintf fs/seq_file.c:398 [inline]
 seq_printf+0x185/0x280 fs/seq_file.c:413
 input_devices_seq_show+0x14b/0x650 drivers/input/input.c:1184
 seq_read_iter+0x908/0xce0 fs/seq_file.c:272
 seq_read+0x3d9/0x4f0 fs/seq_file.c:162
 pde_read fs/proc/inode.c:321 [inline]
 proc_reg_read+0x1c4/0x2b0 fs/proc/inode.c:333
 vfs_read+0x209/0xa50 fs/read_write.c:494
 ksys_read+0x14a/0x260 fs/read_write.c:634
 __do_sys_read fs/read_write.c:644 [inline]
 __se_sys_read fs/read_write.c:642 [inline]
 __x64_sys_read+0x7b/0x90 fs/read_write.c:642
 do_syscall_64+0x31/0x40 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x61/0xcb
RIP: 0033:0x7fbaadbf7159
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:00007fbaac650028 EFLAGS: 00000246 ORIG_RAX: 0000000000000000
RAX: ffffffffffffffda RBX: 00007fbaade7efa0 RCX: 00007fbaadbf7159
RDX: 0000000000002020 RSI: 0000200000000300 RDI: 0000000000000005
RBP: 00007fbaadc8e03b R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fbaade7f038 R14: 00007fbaade7efa0 R15: 00007fff76b6a448

Allocated by task 274:
 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_kmalloc mm/kasan/common.c:509 [inline]
 __kasan_kmalloc+0xd4/0x100 mm/kasan/common.c:518
 kasan_kmalloc include/linux/kasan.h:254 [inline]
 kmem_cache_alloc_trace+0x179/0x2e0 mm/slub.c:2979
 kmalloc include/linux/slab.h:555 [inline]
 kzalloc include/linux/slab.h:667 [inline]
 xpad_probe+0x427/0x1d30 drivers/input/joystick/xpad.c:1784
 usb_probe_interface+0x60f/0xb20 drivers/usb/core/driver.c:397
 really_probe+0x3bf/0xa60 drivers/base/dd.c:562
 driver_probe_device+0xe1/0x190 drivers/base/dd.c:752
 __device_attach_driver+0x282/0x3f0 drivers/base/dd.c:863
 bus_for_each_drv+0x184/0x210 drivers/base/bus.c:433
 __device_attach+0x2a8/0x410 drivers/base/dd.c:932
 device_initial_probe+0x1a/0x20 drivers/base/dd.c:981
 bus_probe_device+0xc0/0x1e0 drivers/base/bus.c:493
 device_add+0x8ce/0xc00 drivers/base/core.c:3273
 usb_set_configuration+0x1a76/0x1fe0 drivers/usb/core/message.c:2219
 usb_generic_driver_probe+0x91/0x150 drivers/usb/core/generic.c:238
 usb_probe_device+0x143/0x250 drivers/usb/core/driver.c:294
 really_probe+0x3bf/0xa60 drivers/base/dd.c:562
 driver_probe_device+0xe1/0x190 drivers/base/dd.c:752
 __device_attach_driver+0x282/0x3f0 drivers/base/dd.c:863
 bus_for_each_drv+0x184/0x210 drivers/base/bus.c:433
 __device_attach+0x2a8/0x410 drivers/base/dd.c:932
 device_initial_probe+0x1a/0x20 drivers/base/dd.c:981
 bus_probe_device+0xc0/0x1e0 drivers/base/bus.c:493
 device_add+0x8ce/0xc00 drivers/base/core.c:3273
 usb_new_device+0x9ba/0x1460 drivers/usb/core/hub.c:2659
 hub_port_connect drivers/usb/core/hub.c:5504 [inline]
 hub_port_connect_change drivers/usb/core/hub.c:5644 [inline]
 port_event drivers/usb/core/hub.c:5810 [inline]
 hub_event+0x2790/0x4220 drivers/usb/core/hub.c:5892
 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

Freed by task 19:
 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]
 kfree+0xc0/0x270 mm/slub.c:4196
 skb_free_head net/core/skbuff.c:606 [inline]
 skb_release_data+0x53b/0x690 net/core/skbuff.c:626
 skb_release_all net/core/skbuff.c:680 [inline]
 __kfree_skb net/core/skbuff.c:694 [inline]
 kfree_skb+0xb9/0x2f0 net/core/skbuff.c:713
 ip6_mc_input+0x22b/0x290 net/ipv6/ip6_input.c:574
 dst_input include/net/dst.h:461 [inline]
 ip6_rcv_finish+0x18c/0x360 net/ipv6/ip6_input.c:80
 NF_HOOK include/linux/netfilter.h:299 [inline]
 ipv6_rcv+0xf0/0x230 net/ipv6/ip6_input.c:301
 __netif_receive_skb_one_core net/core/dev.c:5413 [inline]
 __netif_receive_skb+0xc8/0x280 net/core/dev.c:5527
 process_backlog+0x351/0x600 net/core/dev.c:6434
 napi_poll net/core/dev.c:6885 [inline]
 net_rx_action+0x48d/0xed0 net/core/dev.c:6955
 __do_softirq+0x255/0x563 kernel/softirq.c:309

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]
 schedule_work include/linux/workqueue.h:576 [inline]
 xpad360w_process_packet drivers/input/joystick/xpad.c:853 [inline]
 xpad_irq_in+0xd26/0x1a60 drivers/input/joystick/xpad.c:991
 __usb_hcd_giveback_urb+0x32f/0x4f0 drivers/usb/core/hcd.c:1672
 usb_hcd_giveback_urb+0x11d/0x3f0 drivers/usb/core/hcd.c:1746
 dummy_timer+0xa3a/0x32d0 drivers/usb/gadget/udc/dummy_hcd.c:2000
 call_timer_fn+0x38/0x290 kernel/time/timer.c:1450
 expire_timers kernel/time/timer.c:1495 [inline]
 __run_timers+0x637/0x9a0 kernel/time/timer.c:1789
 run_timer_softirq+0x6a/0xf0 kernel/time/timer.c:1802
 __do_softirq+0x255/0x563 kernel/softirq.c:309

Second to 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]
 schedule_work include/linux/workqueue.h:576 [inline]
 xpad360w_process_packet drivers/input/joystick/xpad.c:853 [inline]
 xpad_irq_in+0xd26/0x1a60 drivers/input/joystick/xpad.c:991
 __usb_hcd_giveback_urb+0x32f/0x4f0 drivers/usb/core/hcd.c:1672
 usb_hcd_giveback_urb+0x11d/0x3f0 drivers/usb/core/hcd.c:1746
 dummy_timer+0xa3a/0x32d0 drivers/usb/gadget/udc/dummy_hcd.c:2000
 call_timer_fn+0x38/0x290 kernel/time/timer.c:1450
 expire_timers kernel/time/timer.c:1495 [inline]
 __run_timers+0x637/0x9a0 kernel/time/timer.c:1789
 run_timer_softirq+0x6a/0xf0 kernel/time/timer.c:1802
 __do_softirq+0x255/0x563 kernel/softirq.c:309

The buggy address belongs to the object at ffff88812725dc00
 which belongs to the cache kmalloc-512 of size 512
The buggy address is located 376 bytes inside of
 512-byte region [ffff88812725dc00, ffff88812725de00)
The buggy address belongs to the page:
page:ffffea00049c9700 refcount:1 mapcount:0 mapping:0000000000000000 index:0xffff88812725f800 pfn:0x12725c
head:ffffea00049c9700 order:2 compound_mapcount:0 compound_pincount:0
flags: 0x4000000000010200(slab|head)
raw: 4000000000010200 ffffea000433b808 ffffea00042f0608 ffff888100043080
raw: ffff88812725f800 000000000010000f 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 283, ts 31183771813, 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_trace+0x1a8/0x2e0 mm/slub.c:2977
 kmalloc include/linux/slab.h:555 [inline]
 kzalloc include/linux/slab.h:667 [inline]
 inetdev_init+0x81/0x490 net/ipv4/devinet.c:259
 inetdev_event+0x1f4/0x1010 net/ipv4/devinet.c:1544
 notifier_call_chain kernel/notifier.c:83 [inline]
 raw_notifier_call_chain+0x90/0x100 kernel/notifier.c:410
 call_netdevice_notifiers_info net/core/dev.c:2052 [inline]
 call_netdevice_notifiers_extack net/core/dev.c:2064 [inline]
 call_netdevice_notifiers+0x119/0x190 net/core/dev.c:2078
 register_netdevice+0x100a/0x13a0 net/core/dev.c:10098
 veth_newlink+0x854/0xb60 drivers/net/veth.c:1387
 __rtnl_newlink net/core/rtnetlink.c:3494 [inline]
 rtnl_newlink+0x1307/0x1830 net/core/rtnetlink.c:3542
 rtnetlink_rcv_msg+0x9e9/0xca0 net/core/rtnetlink.c:5622
 netlink_rcv_skb+0x1e9/0x430 net/netlink/af_netlink.c:2508
page_owner free stack trace missing

Memory state around the buggy address:
 ffff88812725dc00: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff88812725dc80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff88812725dd00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                                                                ^
 ffff88812725dd80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff88812725de00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
==================================================================
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 283, ts 31183771813, free_ts 0
page_owner free stack trace missing

Crashes (2):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/09/11 18:26 android13-5.10-lts 452567d1985b b6a5eeb7 .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-5-10 KASAN: use-after-free Read in seq_printf
2026/08/30 00:44 android13-5.10-lts 174d3ccb72b8 2f52988a .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-5-10 KASAN: use-after-free Read in seq_printf
* Struck through repros no longer work on HEAD.