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KASAN: slab-out-of-bounds Read in seq_printf

Status: premoderation: reported on 2025/09/15 09:58
Reported-by: syzbot+eece2fa44cc502860221@syzkaller.appspotmail.com
First crash: 49d, last: 44d
▶ ▼ Similar bugs (6)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
android-5-10 KASAN: use-after-free Read in seq_printf 19 15 40d 147d 0/2 premoderation: reported on 2025/06/08 22:35
upstream KASAN: slab-out-of-bounds Read in seq_printf fs 19 5 175d 281d 0/29 auto-obsoleted due to no activity on 2025/08/09 17:54
upstream KMSAN: uninit-value in seq_printf (2) fs 7 C 99 1237d 1503d 0/29 auto-closed as invalid on 2022/09/30 02:43
upstream KMSAN: kernel-infoleak in __skb_datagram_iter net 9 68 769d 874d 23/29 fixed on 2023/09/28 17:51
upstream KASAN: slab-use-after-free Read in seq_printf fs 19 2 7d21h 27d 0/29 moderation: reported on 2025/10/07 11:49
android-5-15 KASAN: use-after-free Read in seq_printf 19 1 45d 45d 0/2 premoderation: reported on 2025/09/18 23:28

Sample crash report:
input: syz0 as /devices/virtual/input/input37
==================================================================
BUG: KASAN: slab-out-of-bounds in string_nocheck lib/vsprintf.c:643 [inline]
BUG: KASAN: slab-out-of-bounds in string+0x21f/0x2b0 lib/vsprintf.c:725
Read of size 1 at addr ffff8881321600c9 by task syz.1.3094/8143

CPU: 0 PID: 8143 Comm: syz.1.3094 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/12/2025
Call Trace:
 <TASK>
 __dump_stack+0x21/0x24 lib/dump_stack.c:88
 dump_stack_lvl+0xee/0x150 lib/dump_stack.c:106
 print_address_description+0x71/0x1e0 mm/kasan/report.c:316
 print_report+0x4a/0x60 mm/kasan/report.c:418
 kasan_report+0x122/0x150 mm/kasan/report.c:522
 __asan_report_load1_noabort+0x14/0x20 mm/kasan/report_generic.c:348
 string_nocheck lib/vsprintf.c:643 [inline]
 string+0x21f/0x2b0 lib/vsprintf.c:725
 vsnprintf+0xed9/0x1960 lib/vsprintf.c:2805
 seq_vprintf fs/seq_file.c:391 [inline]
 seq_printf+0x175/0x260 fs/seq_file.c:406
 input_devices_seq_show+0x1a6/0x650 drivers/input/input.c:1204
 seq_read_iter+0x9c8/0xdd0 fs/seq_file.c:272
 seq_read+0x159/0x1f0 fs/seq_file.c:162
 pde_read fs/proc/inode.c:316 [inline]
 proc_reg_read+0x1e4/0x2d0 fs/proc/inode.c:328
 vfs_read+0x26e/0x8c0 fs/read_write.c:468
 ksys_read+0x140/0x240 fs/read_write.c:613
 __do_sys_read fs/read_write.c:623 [inline]
 __se_sys_read fs/read_write.c:621 [inline]
 __x64_sys_read+0x7b/0x90 fs/read_write.c:621
 x64_sys_call+0x2f/0x9a0 arch/x86/include/generated/asm/syscalls_64.h:1
 do_syscall_x64 arch/x86/entry/common.c:51 [inline]
 do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:81
 entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7f9d39d8eba9
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:00007f9d3ac7e038 EFLAGS: 00000246 ORIG_RAX: 0000000000000000
RAX: ffffffffffffffda RBX: 00007f9d39fd5fa0 RCX: 00007f9d39d8eba9
RDX: 0000000000002020 RSI: 0000200000002300 RDI: 0000000000000003
RBP: 00007f9d39e11e19 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f9d39fd6038 R14: 00007f9d39fd5fa0 R15: 00007ffdb68568d8
 </TASK>

Allocated by task 0:
 kasan_save_stack mm/kasan/common.c:45 [inline]
 kasan_set_track+0x4b/0x70 mm/kasan/common.c:52
 kasan_save_alloc_info+0x25/0x30 mm/kasan/generic.c:505
 ____kasan_kmalloc mm/kasan/common.c:379 [inline]
 __kasan_kmalloc+0x95/0xb0 mm/kasan/common.c:388
 kasan_kmalloc include/linux/kasan.h:212 [inline]
 kmalloc_trace+0x40/0xb0 mm/slab_common.c:1033
 kmalloc include/linux/slab.h:563 [inline]
 dummy_urb_enqueue+0x7b/0x7b0 drivers/usb/gadget/udc/dummy_hcd.c:1273
 usb_hcd_submit_urb+0x336/0x1830 drivers/usb/core/hcd.c:1560
 usb_submit_urb+0x122d/0x1900 drivers/usb/core/urb.c:596
 hid_irq_in+0x50c/0x6b0 drivers/hid/usbhid/hid-core.c:322
 __usb_hcd_giveback_urb+0x364/0x520 drivers/usb/core/hcd.c:1675
 usb_hcd_giveback_urb+0x11c/0x410 drivers/usb/core/hcd.c:1758
 dummy_timer+0x86f/0x2ea0 drivers/usb/gadget/udc/dummy_hcd.c:1994
 __run_hrtimer kernel/time/hrtimer.c:1690 [inline]
 __hrtimer_run_queues+0x3cd/0x9f0 kernel/time/hrtimer.c:1754
 hrtimer_run_softirq+0x19b/0x260 kernel/time/hrtimer.c:1771
 handle_softirqs+0x1d7/0x600 kernel/softirq.c:642
 __do_softirq kernel/softirq.c:680 [inline]
 invoke_softirq kernel/softirq.c:497 [inline]
 __irq_exit_rcu+0x52/0xf0 kernel/softirq.c:729
 irq_exit_rcu+0x9/0x10 kernel/softirq.c:741
 instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1118 [inline]
 sysvec_apic_timer_interrupt+0xa9/0xc0 arch/x86/kernel/apic/apic.c:1118
 asm_sysvec_apic_timer_interrupt+0x1b/0x20 arch/x86/include/asm/idtentry.h:691

Freed by task 0:
 kasan_save_stack mm/kasan/common.c:45 [inline]
 kasan_set_track+0x4b/0x70 mm/kasan/common.c:52
 kasan_save_free_info+0x31/0x50 mm/kasan/generic.c:516
 ____kasan_slab_free+0x132/0x180 mm/kasan/common.c:241
 __kasan_slab_free+0x11/0x20 mm/kasan/common.c:249
 kasan_slab_free include/linux/kasan.h:178 [inline]
 slab_free_hook mm/slub.c:1745 [inline]
 slab_free_freelist_hook+0xc2/0x190 mm/slub.c:1771
 slab_free mm/slub.c:3686 [inline]
 __kmem_cache_free+0xb7/0x1b0 mm/slub.c:3702
 kfree+0x6f/0xf0 mm/slab_common.c:990
 dummy_timer+0x7e5/0x2ea0 drivers/usb/gadget/udc/dummy_hcd.c:1988
 __run_hrtimer kernel/time/hrtimer.c:1690 [inline]
 __hrtimer_run_queues+0x3cd/0x9f0 kernel/time/hrtimer.c:1754
 hrtimer_run_softirq+0x19b/0x260 kernel/time/hrtimer.c:1771
 handle_softirqs+0x1d7/0x600 kernel/softirq.c:642
 __do_softirq kernel/softirq.c:680 [inline]
 invoke_softirq kernel/softirq.c:497 [inline]
 __irq_exit_rcu+0x52/0xf0 kernel/softirq.c:729
 irq_exit_rcu+0x9/0x10 kernel/softirq.c:741
 instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1118 [inline]
 sysvec_apic_timer_interrupt+0xa9/0xc0 arch/x86/kernel/apic/apic.c:1118
 asm_sysvec_apic_timer_interrupt+0x1b/0x20 arch/x86/include/asm/idtentry.h:691

The buggy address belongs to the object at ffff888132160000
 which belongs to the cache kmalloc-128 of size 128
The buggy address is located 73 bytes to the right of
 128-byte region [ffff888132160000, ffff888132160080)

The buggy address belongs to the physical page:
page:ffffea0004c85800 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x132160
flags: 0x4000000000000200(slab|zone=1)
raw: 4000000000000200 0000000000000000 dead000000000122 ffff888100042a80
raw: 0000000000000000 0000000000100010 00000001ffffffff 0000000000000000
page dumped because: kasan: bad access detected
page_owner tracks the page as allocated
page last allocated via order 0, migratetype Unmovable, gfp_mask 0x112a20(GFP_ATOMIC|__GFP_NOWARN|__GFP_NORETRY|__GFP_HARDWALL), pid 0, tgid 0 (swapper/0), ts 149645557332, free_ts 149374063295
 set_page_owner include/linux/page_owner.h:33 [inline]
 post_alloc_hook+0x1f5/0x210 mm/page_alloc.c:2643
 prep_new_page+0x1c/0x110 mm/page_alloc.c:2650
 get_page_from_freelist+0x2c7b/0x2cf0 mm/page_alloc.c:4554
 __alloc_pages+0x1c3/0x450 mm/page_alloc.c:5868
 alloc_slab_page+0x6e/0xf0 include/linux/gfp.h:-1
 allocate_slab mm/slub.c:1962 [inline]
 new_slab+0x98/0x3d0 mm/slub.c:2015
 ___slab_alloc+0x6f6/0xb50 mm/slub.c:3203
 __slab_alloc+0x5e/0xa0 mm/slub.c:3302
 slab_alloc_node mm/slub.c:3387 [inline]
 __kmem_cache_alloc_node+0x203/0x2c0 mm/slub.c:3462
 kmalloc_trace+0x29/0xb0 mm/slab_common.c:1028
 kmalloc include/linux/slab.h:563 [inline]
 dummy_urb_enqueue+0x7b/0x7b0 drivers/usb/gadget/udc/dummy_hcd.c:1273
 usb_hcd_submit_urb+0x336/0x1830 drivers/usb/core/hcd.c:1560
 usb_submit_urb+0x122d/0x1900 drivers/usb/core/urb.c:596
 hid_irq_in+0x50c/0x6b0 drivers/hid/usbhid/hid-core.c:322
 __usb_hcd_giveback_urb+0x364/0x520 drivers/usb/core/hcd.c:1675
 usb_hcd_giveback_urb+0x11c/0x410 drivers/usb/core/hcd.c:1758
page last free stack trace:
 reset_page_owner include/linux/page_owner.h:26 [inline]
 free_pages_prepare mm/page_alloc.c:1551 [inline]
 free_pcp_prepare mm/page_alloc.c:1625 [inline]
 free_unref_page_prepare+0x742/0x750 mm/page_alloc.c:3589
 free_unref_page_list+0x112/0x8b0 mm/page_alloc.c:3740
 release_pages+0xad1/0xb20 mm/swap.c:1043
 free_pages_and_swap_cache+0x86/0xa0 mm/swap_state.c:315
 tlb_batch_pages_flush mm/mmu_gather.c:59 [inline]
 tlb_flush_mmu_free mm/mmu_gather.c:254 [inline]
 tlb_flush_mmu mm/mmu_gather.c:261 [inline]
 tlb_finish_mmu+0x1aa/0x370 mm/mmu_gather.c:361
 exit_mmap+0x3dd/0xb60 mm/mmap.c:3378
 __mmput+0x93/0x320 kernel/fork.c:1300
 mmput+0x4b/0x150 kernel/fork.c:1323
 exit_mm kernel/exit.c:568 [inline]
 do_exit+0x981/0x2650 kernel/exit.c:873
 do_group_exit+0x210/0x2d0 kernel/exit.c:1028
 get_signal+0x13b5/0x1520 kernel/signal.c:2889
 arch_do_signal_or_restart+0xb0/0x1030 arch/x86/kernel/signal.c:871
 exit_to_user_mode_loop+0x7a/0xb0 kernel/entry/common.c:174
 exit_to_user_mode_prepare+0x5a/0xa0 kernel/entry/common.c:210
 __syscall_exit_to_user_mode_work kernel/entry/common.c:292 [inline]
 syscall_exit_to_user_mode+0x1a/0x30 kernel/entry/common.c:303
 do_syscall_64+0x58/0xa0 arch/x86/entry/common.c:87

Memory state around the buggy address:
 ffff88813215ff80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
 ffff888132160000: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff888132160080: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
                                              ^
 ffff888132160100: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff888132160180: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
==================================================================

Crashes (2):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2025/09/15 09:57 android14-6.1 876f660de856 e2beed91 .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-6-1 KASAN: slab-out-of-bounds Read in seq_printf
2025/09/20 00:56 android14-6.1 ae242b263718 67c37560 .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-6-1 KASAN: use-after-free Read in seq_printf
* Struck through repros no longer work on HEAD.