KASAN: use-after-free Read in seq_printf (2)

Status: upstream: reported C repro on 2026/10/12 05:38
Reported-by: syzbot+36e8eafa46be129796a8@syzkaller.appspotmail.com
First crash: 48d, last: 17h35m
▶ ▼ Similar bugs (14)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
linux-5.15 KASAN: use-after-free Read in seq_printf 19 2 4d18h 19d 0/3 upstream: reported on 2026/09/23 14:29
android-5-10 KASAN: use-after-free Read in seq_printf (3) 19 syz, C 47 7h52m 9h21m 0/2 upstream: reported C repro on 2026/10/12 19:47
android-5-10 KASAN: use-after-free Read in seq_printf 19 15 383d 491d 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 519d 624d 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 388d 392d 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 271d 271d 0/2 auto-obsoleted due to no activity on 2026/04/14 16:00
android-6-1 KASAN: use-after-free Read in seq_printf origin:lts 19 syz, C 20 7d22h 18d 0/2 upstream: reported C repro on 2026/09/24 21:21
android-5-15 KASAN: use-after-free Read in seq_printf 19 1 389d 389d 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 1580d 1847d 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 191d 191d 0/2 auto-obsoleted due to no activity on 2026/07/03 17:29
android-6-12 KASAN: slab-use-after-free Read in seq_printf origin:lts 19 syz, C 12 6h22m 19d 0/1 premoderation: reported C repro on 2026/09/23 06:02
upstream KMSAN: kernel-infoleak in __skb_datagram_iter net 9 68 1112d 1217d 23/29 fixed on 2023/09/28 17:51
upstream KASAN: slab-use-after-free Read in seq_printf prio:high fs 19 90 14h38m 24d 0/29 upstream: reported on 2026/09/19 02:15
linux-6.6 KASAN: slab-use-after-free Read in seq_printf 19 1 48d 48d 0/2 upstream: reported on 2026/08/25 13:48

Sample crash report:
printk: console [ttyS0] enabled
==================================================================
BUG: KASAN: use-after-free in string_nocheck lib/vsprintf.c:642 [inline]
BUG: KASAN: use-after-free in string+0x20f/0x2a0 lib/vsprintf.c:724
Read of size 1 at addr ffff888101b8e7d0 by task syz-executor510/303

CPU: 0 PID: 303 Comm: syz-executor510 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/24/2026
Call Trace:
 <TASK>
 __dump_stack+0x21/0x30 lib/dump_stack.c:88
 dump_stack_lvl+0x110/0x170 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+0x10f/0x150 mm/kasan/report.c:444
 __asan_report_load1_noabort+0x14/0x20 mm/kasan/report_generic.c:306
 string_nocheck lib/vsprintf.c:642 [inline]
 string+0x20f/0x2a0 lib/vsprintf.c:724
 vsnprintf+0xec5/0x1990 lib/vsprintf.c:2811
 seq_vprintf fs/seq_file.c:407 [inline]
 seq_printf+0x185/0x280 fs/seq_file.c:422
 show_interrupts+0x91d/0xa90 kernel/irq/proc.c:527
 traverse+0x1f2/0x590 fs/seq_file.c:111
 seq_read_iter+0xbcd/0xce0 fs/seq_file.c:195
 proc_reg_read_iter+0x1be/0x290 fs/proc/inode.c:300
 do_iter_readv_writev+0x477/0x5f0 fs/read_write.c:-1
 do_iter_read+0x1fa/0x780 fs/read_write.c:790
 vfs_readv fs/read_write.c:910 [inline]
 do_preadv+0x233/0x390 fs/read_write.c:1002
 __do_sys_preadv fs/read_write.c:1052 [inline]
 __se_sys_preadv fs/read_write.c:1047 [inline]
 __x64_sys_preadv+0x9e/0xb0 fs/read_write.c:1047
 x64_sys_call+0x4f8/0x9a0 arch/x86/include/generated/asm/syscalls_64.h:296
 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: 0033:0x7f3594ffee39
Code: c0 79 93 eb d5 48 8d 7c 1d 00 eb 99 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 d8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007ffc26a7de48 EFLAGS: 00000246 ORIG_RAX: 0000000000000127
RAX: ffffffffffffffda RBX: 636f7270796d2f2e RCX: 00007f3594ffee39
RDX: 0000000000000001 RSI: 0000200000000140 RDI: 0000000000000006
RBP: 0000000000000001 R08: 0000000000000004 R09: 00007ffc26a7df78
R10: 000000000000ffff R11: 0000000000000246 R12: 00007ffc26a7df68
R13: 0000000000000002 R14: 00007f359508fca0 R15: 0000000000000002
 </TASK>

Allocated by task 1:
 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+0xd4/0x100 mm/kasan/common.c:521
 kasan_kmalloc include/linux/kasan.h:227 [inline]
 __kmalloc_track_caller+0x13c/0x2c0 mm/slub.c:4959
 kvasprintf+0xe3/0x1a0 lib/kasprintf.c:25
 kasprintf+0xdf/0x130 lib/kasprintf.c:59
 uart_add_one_port+0x3aa/0x1b60 drivers/tty/serial/serial_core.c:2962
 serial8250_register_8250_port+0x1302/0x1a90 drivers/tty/serial/8250/8250_core.c:1087
 serial_pnp_probe+0x522/0x710 drivers/tty/serial/8250/8250_pnp.c:482
 pnp_device_probe+0x2d0/0x4b0 drivers/pnp/driver.c:111
 call_driver_probe drivers/base/dd.c:-1 [inline]
 really_probe+0x27d/0x970 drivers/base/dd.c:595
 __driver_probe_device+0x193/0x270 drivers/base/dd.c:755
 driver_probe_device+0x54/0x3e0 drivers/base/dd.c:785
 __driver_attach+0x40e/0x550 drivers/base/dd.c:1164
 bus_for_each_dev+0x17b/0x1f0 drivers/base/bus.c:303
 driver_attach+0x42/0x50 drivers/base/dd.c:1181
 bus_add_driver+0x322/0x560 drivers/base/bus.c:620
 driver_register+0x335/0x440 drivers/base/driver.c:240
 pnp_register_driver+0x7d/0x90 drivers/pnp/driver.c:273
 serial8250_pnp_init+0x15/0x20 drivers/tty/serial/8250/8250_pnp.c:537
 serial8250_init+0xa0/0x170 drivers/tty/serial/8250/8250_core.c:1183
 do_one_initcall+0x1fc/0x5a0 init/main.c:1279
 do_initcall_level+0x174/0x2e0 init/main.c:1352
 do_initcalls+0x50/0xa0 init/main.c:1368
 do_basic_setup+0x81/0x90 init/main.c:1387
 kernel_init_freeable+0x298/0x3d0 init/main.c:1592
 kernel_init+0x1d/0x1b0 init/main.c:1483
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:287

Freed by task 303:
 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
 uart_remove_one_port+0x39d/0x760 drivers/tty/serial/serial_core.c:3085
 serial8250_unregister_port+0xad/0x260 drivers/tty/serial/8250/8250_core.c:1146
 serial_pnp_remove+0x6b/0x90 drivers/tty/serial/8250/8250_pnp.c:500
 pnp_device_remove+0x75/0x250 drivers/pnp/driver.c:133
 __device_release_driver drivers/base/dd.c:1227 [inline]
 device_release_driver_internal+0x4e8/0x7c0 drivers/base/dd.c:1262
 device_driver_detach+0x3b/0x40 drivers/base/dd.c:1298
 unbind_store+0x2e5/0x300 drivers/base/bus.c:193
 drv_attr_store+0x79/0xa0 drivers/base/bus.c:77
 sysfs_kf_write+0x129/0x150 fs/sysfs/file.c:143
 kernfs_fop_write_iter+0x2bd/0x400 fs/kernfs/file.c:296
 call_write_iter include/linux/fs.h:2218 [inline]
 new_sync_write fs/read_write.c:507 [inline]
 vfs_write+0x831/0xfd0 fs/read_write.c:594
 ksys_write+0x14a/0x260 fs/read_write.c:647
 __do_sys_write fs/read_write.c:659 [inline]
 __se_sys_write fs/read_write.c:656 [inline]
 __x64_sys_write+0x7b/0x90 fs/read_write.c:656
 x64_sys_call+0x8ef/0x9a0 arch/x86/include/generated/asm/syscalls_64.h:2
 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

The buggy address belongs to the object at ffff888101b8e7d0
 which belongs to the cache kmalloc-8 of size 8
The buggy address is located 0 bytes inside of
 8-byte region [ffff888101b8e7d0, ffff888101b8e7d8)
The buggy address belongs to the page:
page:ffffea000406e380 refcount:1 mapcount:0 mapping:0000000000000000 index:0xffff888101b8e848 pfn:0x101b8e
flags: 0x4000000000000200(slab|zone=1)
raw: 4000000000000200 ffffea000407fc80 0000000800000008 ffff888100042300
raw: ffff888101b8e848 0000000080660053 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 0x12cc0(GFP_KERNEL|__GFP_NOWARN|__GFP_NORETRY), pid 1, ts 2810699879, free_ts 0
 set_page_owner include/linux/page_owner.h:33 [inline]
 post_alloc_hook+0x192/0x1b0 mm/page_alloc.c:2607
 prep_new_page+0x1c/0x110 mm/page_alloc.c:2613
 get_page_from_freelist+0x2c3a/0x2cd0 mm/page_alloc.c:4487
 __alloc_pages+0x1a2/0x460 mm/page_alloc.c:5824
 alloc_slab_page mm/slub.c:-1 [inline]
 allocate_slab mm/slub.c:1937 [inline]
 new_slab+0xa0/0x4d0 mm/slub.c:2000
 ___slab_alloc+0x3ac/0x840 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]
 __kmalloc+0x16a/0x2c0 mm/slub.c:4432
 kmalloc include/linux/slab.h:624 [inline]
 acpi_os_allocate include/acpi/platform/aclinuxex.h:52 [inline]
 acpi_ex_allocate_name_string drivers/acpi/acpica/exnames.c:66 [inline]
 acpi_ex_get_name_string+0x5a9/0xca0 drivers/acpi/acpica/exnames.c:367
 acpi_ds_create_operand+0x168/0x8b0 drivers/acpi/acpica/dsutils.c:446
 acpi_ds_evaluate_name_path+0x15a/0x420 drivers/acpi/acpica/dsutils.c:778
 acpi_ds_exec_end_op+0x255/0x1190 drivers/acpi/acpica/dswexec.c:374
 acpi_ps_parse_loop+0xbff/0x19f0 drivers/acpi/acpica/psloop.c:525
 acpi_ps_parse_aml+0x214/0x9a0 drivers/acpi/acpica/psparse.c:475
 acpi_ps_execute_method+0x681/0x7b0 drivers/acpi/acpica/psxface.c:190
 acpi_ns_evaluate+0x650/0xa20 drivers/acpi/acpica/nseval.c:205
page_owner free stack trace missing

Memory state around the buggy address:
 ffff888101b8e680: fc fc 06 fc fc fc fc 05 fc fc fc fc fa fc fc fc
 ffff888101b8e700: fc 06 fc fc fc fc fb fc fc fc fc 03 fc fc fc fc
>ffff888101b8e780: fa fc fc fc fc fa fc fc fc fc fa fc fc fc fc 00

Crashes (16):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/10/12 05:29 android13-5.15-lts d6c8aee048e0 4f92358f .config strace log report syz / log C [disk image] [vmlinux] [kernel image] ci2-android-5-15 KASAN: use-after-free Read in seq_printf
2026/10/12 11:33 android13-5.15-lts d6c8aee048e0 4f92358f .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-5-15 KASAN: use-after-free Read in seq_printf
2026/10/12 03:26 android13-5.15-lts d6c8aee048e0 4f92358f .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-5-15 KASAN: use-after-free Read in seq_printf
2026/10/11 18:43 android13-5.15-lts d6c8aee048e0 4f92358f .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-5-15 KASAN: use-after-free Read in seq_printf
2026/10/10 18:36 android13-5.15-lts d6c8aee048e0 4f92358f .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-5-15 KASAN: use-after-free Read in seq_printf
2026/10/08 18:15 android13-5.15-lts d6c8aee048e0 b2734a59 .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-5-15 KASAN: use-after-free Read in seq_printf
2026/09/27 10:02 android13-5.15-lts 776976664f31 a3c7249d .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-5-15 KASAN: use-after-free Read in seq_printf
2026/09/27 03:18 android13-5.15-lts 776976664f31 a3c7249d .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-5-15 KASAN: use-after-free Read in seq_printf
2026/09/26 22:40 android13-5.15-lts 776976664f31 a3c7249d .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-5-15 KASAN: use-after-free Read in seq_printf
2026/09/26 22:14 android13-5.15-lts 776976664f31 a3c7249d .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-5-15 KASAN: use-after-free Read in seq_printf
2026/09/26 01:03 android13-5.15-lts 81cf8006a12f f281d9d2 .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-5-15 KASAN: use-after-free Read in seq_printf
2026/09/25 14:24 android13-5.15-lts 81cf8006a12f f281d9d2 .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-5-15 KASAN: use-after-free Read in seq_printf
2026/09/24 12:31 android13-5.15-lts 5bfe2b8c1439 0281b448 .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-5-15 KASAN: use-after-free Read in seq_printf
2026/09/18 15:42 android13-5.15-lts 5bfe2b8c1439 853b104b .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-5-15 KASAN: use-after-free Read in seq_printf
2026/08/26 02:29 android13-5.15-lts 771777348d20 6a91adb4 .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-5-15 KASAN: use-after-free Read in seq_printf
2026/08/26 02:29 android13-5.15-lts 771777348d20 6a91adb4 .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-5-15 KASAN: use-after-free Read in seq_printf
* Struck through repros no longer work on HEAD.