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BUG: KASAN: slab-use-after-free in string_nocheck lib/vsprintf.c:648 [inline]
BUG: KASAN: slab-use-after-free in string+0x471/0x4d0 lib/vsprintf.c:730
Read of size 1 at addr ffff8880261c4c60 by task syz.2.1573/11662

CPU: 2 UID: 0 PID: 11662 Comm: syz.2.1573 Tainted: G             L      syzkaller #0 PREEMPT(full) 
Tainted: [L]=SOFTLOCKUP
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2 04/01/2014
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
 string_nocheck lib/vsprintf.c:648 [inline]
 string+0x471/0x4d0 lib/vsprintf.c:730
 vsnprintf+0x422/0x1300 lib/vsprintf.c:2945
 seq_vprintf fs/seq_file.c:392 [inline]
 seq_printf+0x1a4/0x250 fs/seq_file.c:407
 irq_seq_show+0x390/0x8b0 kernel/irq/proc.c:601
 seq_read_iter+0xbce/0x1270 fs/seq_file.c:273
 proc_reg_read_iter+0x220/0x310 fs/proc/inode.c:299
 new_sync_read fs/read_write.c:493 [inline]
 vfs_read+0x82e/0xb40 fs/read_write.c:574
 ksys_read+0x12a/0x250 fs/read_write.c:716
 do_syscall_32_irqs_on arch/x86/entry/syscall_32.c:83 [inline]
 __do_fast_syscall_32+0xe7/0x970 arch/x86/entry/syscall_32.c:307
 do_fast_syscall_32+0x32/0x70 arch/x86/entry/syscall_32.c:332
 entry_SYSENTER_compat_after_hwframe+0x84/0x8e
RIP: 0023:0xf706efec
Code: Unable to access opcode bytes at 0xf706efc2.
RSP: 002b:00000000f543c50c EFLAGS: 00000292 ORIG_RAX: 0000000000000003
RAX: ffffffffffffffda RBX: 0000000000000007 RCX: 0000000080000400
RDX: 000000000000fdef RSI: 0000000000000000 RDI: 0000000000000000
RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000292 R12: 0000000000000000
R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000
 </TASK>

Allocated by task 5733:
 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+0xaa/0xb0 mm/kasan/common.c:415
 kasan_kmalloc include/linux/kasan.h:263 [inline]
 __do_kmalloc_node mm/slub.c:5334 [inline]
 __kmalloc_node_noprof+0x339/0x830 mm/slub.c:5346
 _kmalloc_node_noprof include/linux/slab.h:1197 [inline]
 __vmalloc_area_node mm/vmalloc.c:3893 [inline]
 __vmalloc_node_range_noprof+0x409/0x1630 mm/vmalloc.c:4104
 __vmalloc_node_noprof+0xad/0xf0 mm/vmalloc.c:4165
 alloc_counters net/ipv6/netfilter/ip6_tables.c:815 [inline]
 compat_copy_entries_to_user net/ipv6/netfilter/ip6_tables.c:1567 [inline]
 compat_get_entries+0x3b0/0x860 net/ipv6/netfilter/ip6_tables.c:1610
 do_ip6t_get_ctl+0x5c1/0xb00 net/ipv6/netfilter/ip6_tables.c:1675
 nf_getsockopt+0x7c/0xe0 net/netfilter/nf_sockopt.c:116
 ipv6_getsockopt+0x207/0x2a0 net/ipv6/ipv6_sockglue.c:1464
 tcp_getsockopt+0xa1/0x110 net/ipv4/tcp.c:4864
 do_sock_getsockopt+0x50a/0x6e0 net/socket.c:2474
 __sys_getsockopt+0x133/0x1d0 net/socket.c:2505
 __do_compat_sys_socketcall net/compat.c:493 [inline]
 __se_compat_sys_socketcall net/compat.c:422 [inline]
 __ia32_compat_sys_socketcall+0x6af/0x770 net/compat.c:422
 do_syscall_32_irqs_on arch/x86/entry/syscall_32.c:83 [inline]
 __do_fast_syscall_32+0xe7/0x970 arch/x86/entry/syscall_32.c:307
 do_fast_syscall_32+0x32/0x70 arch/x86/entry/syscall_32.c:332
 entry_SYSENTER_compat_after_hwframe+0x84/0x8e

Freed by task 5733:
 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+0x5f/0x80 mm/kasan/common.c:285
 kasan_slab_free include/linux/kasan.h:235 [inline]
 slab_free_hook mm/slub.c:2677 [inline]
 slab_free mm/slub.c:6377 [inline]
 kfree+0x22b/0x6c0 mm/slub.c:6692
 vfree mm/vmalloc.c:3511 [inline]
 vfree+0x12e/0x750 mm/vmalloc.c:3484
 compat_copy_entries_to_user net/ipv6/netfilter/ip6_tables.c:1580 [inline]
 compat_get_entries+0x5d2/0x860 net/ipv6/netfilter/ip6_tables.c:1610
 do_ip6t_get_ctl+0x5c1/0xb00 net/ipv6/netfilter/ip6_tables.c:1675
 nf_getsockopt+0x7c/0xe0 net/netfilter/nf_sockopt.c:116
 ipv6_getsockopt+0x207/0x2a0 net/ipv6/ipv6_sockglue.c:1464
 tcp_getsockopt+0xa1/0x110 net/ipv4/tcp.c:4864
 do_sock_getsockopt+0x50a/0x6e0 net/socket.c:2474
 __sys_getsockopt+0x133/0x1d0 net/socket.c:2505
 __do_compat_sys_socketcall net/compat.c:493 [inline]
 __se_compat_sys_socketcall net/compat.c:422 [inline]
 __ia32_compat_sys_socketcall+0x6af/0x770 net/compat.c:422
 do_syscall_32_irqs_on arch/x86/entry/syscall_32.c:83 [inline]
 __do_fast_syscall_32+0xe7/0x970 arch/x86/entry/syscall_32.c:307
 do_fast_syscall_32+0x32/0x70 arch/x86/entry/syscall_32.c:332
 entry_SYSENTER_compat_after_hwframe+0x84/0x8e

The buggy address belongs to the object at ffff8880261c4c60
 which belongs to the cache kmalloc-8 of size 8
The buggy address is located 0 bytes inside of
 freed 8-byte region [ffff8880261c4c60, ffff8880261c4c68)

The buggy address belongs to the physical page:
page: refcount:0 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x261c4
flags: 0xfff00000000000(node=0|zone=1|lastcpupid=0x7ff)
page_type: f5(slab)
raw: 00fff00000000000 ffff88801bc42500 dead000000000100 dead000000000122
raw: 0000000000000000 0000000800800080 00000000f5000000 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 0xd2cc0(GFP_KERNEL|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC), pid 1, tgid 1 (swapper/0), ts 5200980168, free_ts 0
 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+0xf48/0x3530 mm/page_alloc.c:3946
 __alloc_frozen_pages_noprof+0x299/0x2dc0 mm/page_alloc.c:5304
 alloc_slab_page mm/slub.c:3266 [inline]
 allocate_slab mm/slub.c:3380 [inline]
 new_slab+0xa2/0x640 mm/slub.c:3426
 refill_objects+0xe3/0x410 mm/slub.c:7310
 refill_sheaf mm/slub.c:2804 [inline]
 __pcs_replace_empty_main+0x376/0x680 mm/slub.c:4675
 alloc_from_pcs mm/slub.c:4773 [inline]
 slab_alloc_node mm/slub.c:4905 [inline]
 __do_kmalloc_node mm/slub.c:5333 [inline]
 __kmalloc_node_track_caller_noprof+0x679/0x830 mm/slub.c:5471
 __kmemdup_nul mm/util.c:64 [inline]
 kstrdup+0x51/0xe0 mm/util.c:84
 kstrdup_const+0x63/0x80 mm/util.c:104
 __kernfs_new_node+0x9b/0xa10 fs/kernfs/dir.c:661
 kernfs_new_node+0x117/0x150 fs/kernfs/dir.c:751
 kernfs_create_link+0xcc/0x240 fs/kernfs/symlink.c:39
 sysfs_do_create_link_sd+0x90/0x140 fs/sysfs/symlink.c:44
 sysfs_do_create_link fs/sysfs/symlink.c:80 [inline]
 sysfs_create_link+0x61/0xc0 fs/sysfs/symlink.c:92
 device_create_sys_dev_entry drivers/base/core.c:3583 [inline]
 device_add+0xb62/0x1970 drivers/base/core.c:3727
 tty_register_device_attr+0x388/0x7f0 drivers/tty/tty_io.c:3261
page_owner free stack trace missing

Memory state around the buggy address:
 ffff8880261c4b00: 07 fc fc fc 06 fc fc fc 05 fc fc fc 05 fc fc fc
 ffff8880261c4b80: 05 fc fc fc 05 fc fc fc 00 fc fc fc 07 fc fc fc
>ffff8880261c4c00: 06 fc fc fc 06 fc fc fc 07 fc fc fc fa fc fc fc
                                                       ^
 ffff8880261c4c80: 07 fc fc fc 06 fc fc fc 04 fc fc fc 07 fc fc fc
 ffff8880261c4d00: 07 fc fc fc 07 fc fc fc 00 fc fc fc 00 fc fc fc
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