KASAN: slab-use-after-free Read in str_to_user (2)

Status: upstream: reported on 2026/07/06 01:19
Subsystems: input
Labels: prio:high actionable
[Documentation on labels]
Reported-by: syzbot+aec1962419768c5caf88@syzkaller.appspotmail.com
First crash: 52d, last: 18d
▶ ▼ ✨ AI Jobs (2)
ID Workflow Result Correct Bug Created Started Finished Revision
12181af8 moderation Actionable: ✅ ❓ KASAN: slab-use-after-free Read in str_to_user (2) 2026/07/06 00:36 2026/07/06 00:36 2026/07/06 01:18 93f57954
0b36514c assessment-security DenialOfService: ✅ Exploitable: ✅ FilesystemTrigger: ❌ NetworkTrigger: ❌ PeripheralTrigger: ✅ RemoteTrigger: ❌ Unprivileged: ✅ UserNamespace: ❌ VMGuestTrigger: ❌ VMHostTrigger: ❌ ❓ KASAN: slab-use-after-free Read in str_to_user (2) 2026/07/03 01:08 2026/07/03 01:08 2026/07/03 01:48 93f57954
▶ ▼ Discussions (2)
Title Replies (including bot) Last reply
[PATCH] HID: input: allocate input_dev name/phys/uniq using hid device devres 1 (1) 2026/07/14 12:00
[syzbot] [input?] KASAN: slab-use-after-free Read in str_to_user (2) 0 (1) 2026/07/06 01:19
▶ ▼ Similar bugs (2)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
upstream KASAN: slab-use-after-free Read in str_to_user input prio:normal 19 3 123d 167d 0/29 closed as invalid on 2026/05/19 14:07
linux-6.6 KASAN: slab-use-after-free Read in str_to_user 19 1 18d 18d 0/2 upstream: reported on 2026/08/05 01:22

Sample crash report:
==================================================================
BUG: KASAN: slab-use-after-free in strlen+0x85/0xa0 lib/string.c:402
Read of size 1 at addr ffff888112fec220 by task syz.3.1096/9318

CPU: 1 UID: 0 PID: 9318 Comm: syz.3.1096 Not tainted syzkaller #0 PREEMPT(lazy) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/09/2026
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:94 [inline]
 dump_stack_lvl+0x100/0x190 lib/dump_stack.c:120
 print_address_description mm/kasan/report.c:378 [inline]
 print_report+0x13d/0x4b0 mm/kasan/report.c:482
 kasan_report+0xdf/0x1c0 mm/kasan/report.c:595
 strlen+0x85/0xa0 lib/string.c:402
 __fortify_strlen include/linux/fortify-string.h:218 [inline]
 str_to_user+0x26/0xa0 drivers/input/evdev.c:769
 evdev_do_ioctl+0x1529/0x1b60 drivers/input/evdev.c:1172
 evdev_ioctl_handler drivers/input/evdev.c:1270 [inline]
 evdev_ioctl+0x16f/0x1a0 drivers/input/evdev.c:1279
 vfs_ioctl fs/ioctl.c:51 [inline]
 __do_sys_ioctl fs/ioctl.c:597 [inline]
 __se_sys_ioctl fs/ioctl.c:583 [inline]
 __x64_sys_ioctl+0x18e/0x210 fs/ioctl.c:583
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0x10b/0x7f0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f4fe1cdde59
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:00007f4fe0737028 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00007f4fe1f65fa0 RCX: 00007f4fe1cdde59
RDX: 0000200000003d80 RSI: 0000000080404507 RDI: 0000000000000008
RBP: 00007f4fe1d73e6f R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f4fe1f66038 R14: 00007f4fe1f65fa0 R15: 00007ffc2d29e718
 </TASK>

Allocated by task 5308:
 kasan_save_stack+0x30/0x50 mm/kasan/common.c:57
 kasan_save_track+0x14/0x30 mm/kasan/common.c:78
 poison_kmalloc_redzone mm/kasan/common.c:398 [inline]
 __kasan_kmalloc+0x8f/0xa0 mm/kasan/common.c:415
 kasan_kmalloc include/linux/kasan.h:263 [inline]
 __do_kmalloc_node mm/slub.c:5362 [inline]
 __kmalloc_noprof+0x309/0x7c0 mm/slub.c:5387
 _kmalloc_noprof include/linux/slab.h:973 [inline]
 _kzalloc_noprof include/linux/slab.h:1290 [inline]
 usb_get_configuration+0x1ac/0x4410 drivers/usb/core/config.c:932
 usb_enumerate_device drivers/usb/core/hub.c:2527 [inline]
 usb_new_device+0x580/0x7d0 drivers/usb/core/hub.c:2665
 hub_port_connect drivers/usb/core/hub.c:5567 [inline]
 hub_port_connect_change drivers/usb/core/hub.c:5707 [inline]
 port_event drivers/usb/core/hub.c:5871 [inline]
 hub_event+0x314d/0x4af0 drivers/usb/core/hub.c:5953
 process_one_work+0xa23/0x1940 kernel/workqueue.c:3322
 process_scheduled_works kernel/workqueue.c:3405 [inline]
 worker_thread+0x5ef/0xe50 kernel/workqueue.c:3486
 kthread+0x370/0x450 kernel/kthread.c:436
 ret_from_fork+0x69a/0xc80 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

Freed by task 5418:
 kasan_save_stack+0x30/0x50 mm/kasan/common.c:57
 kasan_save_track+0x14/0x30 mm/kasan/common.c:78
 kasan_save_free_info+0x3b/0x70 mm/kasan/generic.c:584
 poison_slab_object mm/kasan/common.c:253 [inline]
 __kasan_slab_free+0x43/0x70 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+0x20c/0x650 mm/slub.c:6720
 usb_destroy_configuration+0x561/0x700 drivers/usb/core/config.c:896
 usb_release_dev+0x42/0x110 drivers/usb/core/usb.c:494
 device_release+0xd2/0x270 drivers/base/core.c:2636
 kobject_cleanup lib/kobject.c:689 [inline]
 kobject_release lib/kobject.c:720 [inline]
 kref_put include/linux/kref.h:65 [inline]
 kobject_put+0x1f7/0x640 lib/kobject.c:737
 put_device+0x1f/0x30 drivers/base/core.c:3880
 hub_port_connect drivers/usb/core/hub.c:5407 [inline]
 hub_port_connect_change drivers/usb/core/hub.c:5707 [inline]
 port_event drivers/usb/core/hub.c:5871 [inline]
 hub_event+0x1d0c/0x4af0 drivers/usb/core/hub.c:5953
 process_one_work+0xa23/0x1940 kernel/workqueue.c:3322
 process_scheduled_works kernel/workqueue.c:3405 [inline]
 worker_thread+0x5ef/0xe50 kernel/workqueue.c:3486
 kthread+0x370/0x450 kernel/kthread.c:436
 ret_from_fork+0x69a/0xc80 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

The buggy address belongs to the object at ffff888112fec000
 which belongs to the cache kmalloc-1k of size 1024
The buggy address is located 544 bytes inside of
 freed 1024-byte region [ffff888112fec000, ffff888112fec400)

The buggy address belongs to the physical page:
page: refcount:0 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x112fe8
head: order:3 mapcount:0 entire_mapcount:0 nr_pages_mapped:0 pincount:0
flags: 0x200000000000040(head|node=0|zone=2)
page_type: f5(slab)
raw: 0200000000000040 ffff888100041dc0 dead000000000100 dead000000000122
raw: 0000000000000000 0000000800100010 00000000f5000000 0000000000000000
head: 0200000000000040 ffff888100041dc0 dead000000000100 dead000000000122
head: 0000000000000000 0000000800100010 00000000f5000000 0000000000000000
head: 0200000000000003 fffffffffffffe01 00000000ffffffff 00000000ffffffff
head: 0000000000000000 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 0xd20c0(__GFP_IO|__GFP_FS|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC), pid 1, tgid 1 (swapper/0), ts 16487694787, free_ts 14540795040
 set_page_owner include/linux/page_owner.h:32 [inline]
 post_alloc_hook+0xfd/0x120 mm/page_alloc.c:1859
 prep_new_page mm/page_alloc.c:1867 [inline]
 get_page_from_freelist+0xf25/0x3400 mm/page_alloc.c:3946
 __alloc_frozen_pages_noprof+0x28f/0x2b90 mm/page_alloc.c:5304
 alloc_slab_page mm/slub.c:3294 [inline]
 allocate_slab mm/slub.c:3408 [inline]
 new_slab+0xa2/0x670 mm/slub.c:3454
 refill_objects+0xe3/0x410 mm/slub.c:7338
 refill_sheaf mm/slub.c:2832 [inline]
 __pcs_replace_empty_main+0x376/0x680 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+0x60d/0x7c0 mm/slub.c:5387
 _kmalloc_noprof include/linux/slab.h:973 [inline]
 _kzalloc_noprof include/linux/slab.h:1290 [inline]
 __alloc_workqueue+0x1bd/0x1940 kernel/workqueue.c:5827
 alloc_workqueue_va kernel/workqueue.c:5946 [inline]
 alloc_workqueue_noprof+0xc7/0x130 kernel/workqueue.c:5962
 init_netconsole+0xf3a/0x1150 drivers/net/netconsole.c:2418
 do_one_initcall+0x11d/0x700 init/main.c:1347
 do_initcall_level init/main.c:1409 [inline]
 do_initcalls init/main.c:1425 [inline]
 do_basic_setup init/main.c:1445 [inline]
 kernel_init_freeable+0x6ea/0x7b0 init/main.c:1658
 kernel_init+0x1f/0x1e0 init/main.c:1548
 ret_from_fork+0x69a/0xc80 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
page last free pid 11 tgid 11 stack trace:
 reset_page_owner include/linux/page_owner.h:25 [inline]
 __free_pages_prepare mm/page_alloc.c:1406 [inline]
 free_pages_prepare+0x558/0xcb0 mm/page_alloc.c:1451
 __free_contig_range_common.constprop.0+0x12c/0x230 mm/page_alloc.c:6897
 __free_contig_range mm/page_alloc.c:6942 [inline]
 free_pages_bulk+0x126/0x1f0 mm/page_alloc.c:5257
 vm_area_free_pages+0xad/0x2b0 mm/vmalloc.c:3439
 vfree mm/vmalloc.c:3488 [inline]
 vfree+0x107/0x750 mm/vmalloc.c:3462
 delayed_vfree_work+0x56/0x80 mm/vmalloc.c:3392
 process_one_work+0xa23/0x1940 kernel/workqueue.c:3322
 process_scheduled_works kernel/workqueue.c:3405 [inline]
 worker_thread+0x5ef/0xe50 kernel/workqueue.c:3486
 kthread+0x370/0x450 kernel/kthread.c:436
 ret_from_fork+0x69a/0xc80 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:
 ffff888112fec100: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff888112fec180: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff888112fec200: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                               ^
 ffff888112fec280: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff888112fec300: 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
2026/07/01 14:28 https://git.kernel.org/pub/scm/linux/kernel/git/gregkh/usb.git usb-testing dc59e4fea9d8 00a5cf1c .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-usb KASAN: slab-use-after-free Read in str_to_user
2026/08/05 04:34 upstream c21bb4193868 d4abbeac .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce KASAN: slab-out-of-bounds Read in str_to_user
* Struck through repros no longer work on HEAD.