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BUG: KASAN: slab-use-after-free in string_nocheck lib/vsprintf.c:645 [inline]
BUG: KASAN: slab-use-after-free in string+0x204/0x290 lib/vsprintf.c:727
Read of size 1 at addr ffff888021fa8cd0 by task syz.1.23/5987

CPU: 1 PID: 5987 Comm: syz.1.23 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/07/2026
Call Trace:
 <TASK>
 dump_stack_lvl+0x18c/0x250 lib/dump_stack.c:106
 print_address_description mm/kasan/report.c:364 [inline]
 print_report+0xa8/0x210 mm/kasan/report.c:468
 kasan_report+0x117/0x150 mm/kasan/report.c:581
 string_nocheck lib/vsprintf.c:645 [inline]
 string+0x204/0x290 lib/vsprintf.c:727
 vsnprintf+0xf72/0x1ba0 lib/vsprintf.c:2823
 vprintk_store+0x3d9/0xd50 kernel/printk/printk.c:2226
 vprintk_emit+0x117/0x610 kernel/printk/printk.c:2322
 _printk+0xde/0x130 kernel/printk/printk.c:2366
 __setup_irq+0xf92/0x1f30 kernel/irq/manage.c:1837
 request_threaded_irq+0x2c1/0x3a0 kernel/irq/manage.c:2205
 request_irq include/linux/interrupt.h:168 [inline]
 pcl818_attach+0x18c/0x15c0 drivers/comedi/drivers/pcl818.c:998
 comedi_device_attach+0x526/0x710 drivers/comedi/drivers.c:1014
 do_devconfig_ioctl drivers/comedi/comedi_fops.c:872 [inline]
 comedi_unlocked_ioctl+0x6c4/0x1170 drivers/comedi/comedi_fops.c:2178
 vfs_ioctl fs/ioctl.c:51 [inline]
 __do_sys_ioctl fs/ioctl.c:871 [inline]
 __se_sys_ioctl+0xfd/0x170 fs/ioctl.c:857
 do_syscall_x64 arch/x86/entry/common.c:46 [inline]
 do_syscall_64+0x55/0xb0 arch/x86/entry/common.c:76
 entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7fcf36b9f559
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:00007fcf37a04028 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00007fcf36e25fa0 RCX: 00007fcf36b9f559
RDX: 0000200000006080 RSI: 0000000040946400 RDI: 0000000000000003
RBP: 00007fcf36c36b20 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fcf36e26038 R14: 00007fcf36e25fa0 R15: 00007fffb75e5a48
 </TASK>

Allocated by task 1:
 kasan_save_stack mm/kasan/common.c:46 [inline]
 kasan_set_track+0x4e/0x70 mm/kasan/common.c:53
 ____kasan_kmalloc mm/kasan/common.c:375 [inline]
 __kasan_kmalloc+0x8f/0xa0 mm/kasan/common.c:384
 kasan_kmalloc include/linux/kasan.h:198 [inline]
 __do_kmalloc_node mm/slab_common.c:1007 [inline]
 __kmalloc_node_track_caller+0xb4/0x230 mm/slab_common.c:1027
 kvasprintf+0xec/0x1a0 lib/kasprintf.c:25
 kasprintf+0xe3/0x140 lib/kasprintf.c:59
 serial_core_add_one_port drivers/tty/serial/serial_core.c:3176 [inline]
 serial_core_register_port+0x5f7/0x2440 drivers/tty/serial/serial_core.c:3428
 serial8250_register_8250_port+0x160c/0x1f50 drivers/tty/serial/8250/8250_core.c:1144
 serial_pnp_probe+0x577/0x750 drivers/tty/serial/8250/8250_pnp.c:478
 pnp_device_probe+0x305/0x4b0 drivers/pnp/driver.c:111
 call_driver_probe drivers/base/dd.c:-1 [inline]
 really_probe+0x24a/0xae0 drivers/base/dd.c:717
 __driver_probe_device+0x1f5/0x390 drivers/base/dd.c:879
 driver_probe_device+0x4f/0x420 drivers/base/dd.c:909
 __driver_attach+0x444/0x6d0 drivers/base/dd.c:1295
 bus_for_each_dev+0x235/0x2b0 drivers/base/bus.c:370
 bus_add_driver+0x340/0x630 drivers/base/bus.c:723
 driver_register+0x23a/0x310 drivers/base/driver.c:246
 serial8250_init+0x9a/0x170 drivers/tty/serial/8250/8250_core.c:1244
 do_one_initcall+0x242/0x790 init/main.c:1215
 do_initcall_level+0x13d/0x1f0 init/main.c:1277
 do_initcalls+0x69/0xd0 init/main.c:1293
 kernel_init_freeable+0x3d9/0x560 init/main.c:1530
 kernel_init+0x1d/0x1c0 init/main.c:1420
 ret_from_fork+0x48/0x80 arch/x86/kernel/process.c:152
 ret_from_fork_asm+0x11/0x20 arch/x86/entry/entry_64.S:293

Freed by task 5964:
 kasan_save_stack mm/kasan/common.c:46 [inline]
 kasan_set_track+0x4e/0x70 mm/kasan/common.c:53
 kasan_save_free_info+0x28/0x40 mm/kasan/generic.c:522
 ____kasan_slab_free+0x126/0x1f0 mm/kasan/common.c:237
 kasan_slab_free include/linux/kasan.h:164 [inline]
 slab_free_hook mm/slub.c:1833 [inline]
 slab_free_freelist_hook+0x154/0x240 mm/slub.c:1859
 slab_free mm/slub.c:3853 [inline]
 __kmem_cache_free+0xba/0x1f0 mm/slub.c:3866
 serial_core_remove_one_port drivers/tty/serial/serial_core.c:3291 [inline]
 serial_core_unregister_port+0x484/0xb40 drivers/tty/serial/serial_core.c:3465
 serial8250_unregister_port+0xb0/0x280 drivers/tty/serial/8250/8250_core.c:1206
 pnp_device_remove+0x7c/0x250 drivers/pnp/driver.c:133
 device_remove drivers/base/dd.c:626 [inline]
 __device_release_driver drivers/base/dd.c:1351 [inline]
 device_release_driver_internal+0x408/0x6f0 drivers/base/dd.c:1374
 unbind_store+0x1a1/0x1d0 drivers/base/bus.c:244
 kernfs_fop_write_iter+0x3a4/0x520 fs/kernfs/file.c:352
 call_write_iter include/linux/fs.h:2019 [inline]
 new_sync_write fs/read_write.c:491 [inline]
 vfs_write+0x474/0x9a0 fs/read_write.c:584
 ksys_write+0x151/0x260 fs/read_write.c:637
 do_syscall_x64 arch/x86/entry/common.c:46 [inline]
 do_syscall_64+0x55/0xb0 arch/x86/entry/common.c:76
 entry_SYSCALL_64_after_hwframe+0x68/0xd2

The buggy address belongs to the object at ffff888021fa8cd0
 which belongs to the cache kmalloc-8 of size 8
The buggy address is located 0 bytes inside of
 freed 8-byte region [ffff888021fa8cd0, ffff888021fa8cd8)

The buggy address belongs to the physical page:
page:ffffea000087ea00 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x21fa8
anon flags: 0xfff00000000800(slab|node=0|zone=1|lastcpupid=0x7ff)
page_type: 0xffffffff()
raw: 00fff00000000800 ffff888018c41280 0000000000000000 dead000000000001
raw: 0000000000000000 0000000000660066 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, tgid 1 (swapper/0), ts 6611273014, free_ts 0
 set_page_owner include/linux/page_owner.h:31 [inline]
 post_alloc_hook+0x1c1/0x200 mm/page_alloc.c:1582
 prep_new_page mm/page_alloc.c:1589 [inline]
 get_page_from_freelist+0x2181/0x22a0 mm/page_alloc.c:3221
 __alloc_pages+0x1f0/0x460 mm/page_alloc.c:4501
 alloc_page_interleave+0x24/0x1e0 mm/mempolicy.c:2118
 alloc_slab_page+0x5d/0x180 mm/slub.c:1903
 allocate_slab mm/slub.c:2050 [inline]
 new_slab+0x87/0x2d0 mm/slub.c:2103
 ___slab_alloc+0xc5c/0x12f0 mm/slub.c:3275
 __slab_alloc mm/slub.c:3361 [inline]
 __slab_alloc_node mm/slub.c:3414 [inline]
 slab_alloc_node mm/slub.c:3508 [inline]
 __kmem_cache_alloc_node+0x122/0x260 mm/slub.c:3557
 __do_kmalloc_node mm/slab_common.c:1006 [inline]
 __kmalloc_node_track_caller+0xa4/0x230 mm/slab_common.c:1027
 kstrdup+0x3b/0x80 mm/util.c:62
 __kernfs_new_node+0xaa/0x7f0 fs/kernfs/dir.c:620
 kernfs_new_node+0x14c/0x260 fs/kernfs/dir.c:700
 kernfs_create_link+0xa7/0x200 fs/kernfs/symlink.c:39
 sysfs_do_create_link_sd+0x83/0x110 fs/sysfs/symlink.c:44
 device_add_class_symlinks+0x1cf/0x240 drivers/base/core.c:3512
 device_add+0x4f9/0xc40 drivers/base/core.c:3704
page_owner free stack trace missing

Memory state around the buggy address:
 ffff888021fa8b80: fc fc 00 fc fc fc fc 00 fc fc fc fc 04 fc fc fc
 ffff888021fa8c00: fc fa fc fc fc fc fa fc fc fc fc 00 fc fc fc fc
>ffff888021fa8c80: 00 fc fc fc fc fa fc fc fc fc fa fc fc fc fc 05
                                                 ^
 ffff888021fa8d00: fc fc fc fc 05 fc fc fc fc 05 fc fc fc fc fa fc
 ffff888021fa8d80: fc fc fc fa fc fc fc fc fa fc fc fc fc fa fc fc
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