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BUG: KASAN: slab-out-of-bounds in afs_split_string fs/afs/addr_prefs.c:51 [inline]
BUG: KASAN: slab-out-of-bounds in afs_proc_addr_prefs_write+0x123b/0x14e0 fs/afs/addr_prefs.c:415
Read of size 1 at addr ffff88807c2dba70 by task syz.3.7/5911

CPU: 0 UID: 0 PID: 5911 Comm: syz.3.7 Not tainted 6.13.0-rc2-syzkaller-00333-ga0e3919a2df2 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 11/25/2024
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:94 [inline]
 dump_stack_lvl+0x116/0x1f0 lib/dump_stack.c:120
 print_address_description mm/kasan/report.c:378 [inline]
 print_report+0xc3/0x620 mm/kasan/report.c:489
 kasan_report+0xd9/0x110 mm/kasan/report.c:602
 afs_split_string fs/afs/addr_prefs.c:51 [inline]
 afs_proc_addr_prefs_write+0x123b/0x14e0 fs/afs/addr_prefs.c:415
 proc_simple_write+0x114/0x1b0 fs/proc/generic.c:815
 pde_write fs/proc/inode.c:330 [inline]
 proc_reg_write+0x23d/0x330 fs/proc/inode.c:342
 vfs_write+0x24c/0x1150 fs/read_write.c:677
 ksys_write+0x12b/0x250 fs/read_write.c:731
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0xcd/0x250 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f01ca385d19
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:00007f01cb1e7038 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 00007f01ca575fa0 RCX: 00007f01ca385d19
RDX: 000000000000000f RSI: 0000000020000340 RDI: 0000000000000003
RBP: 00007f01ca401a20 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 0000000000000000 R14: 00007f01ca575fa0 R15: 00007ffcfeedd8c8
 </TASK>

Allocated by task 5911:
 kasan_save_stack+0x33/0x60 mm/kasan/common.c:47
 kasan_save_track+0x14/0x30 mm/kasan/common.c:68
 poison_kmalloc_redzone mm/kasan/common.c:377 [inline]
 __kasan_kmalloc+0xaa/0xb0 mm/kasan/common.c:394
 kasan_kmalloc include/linux/kasan.h:260 [inline]
 __do_kmalloc_node mm/slub.c:4298 [inline]
 __kmalloc_node_track_caller_noprof+0x21d/0x520 mm/slub.c:4317
 memdup_user_nul+0x2b/0x110 mm/util.c:305
 proc_simple_write+0xc7/0x1b0 fs/proc/generic.c:812
 pde_write fs/proc/inode.c:330 [inline]
 proc_reg_write+0x23d/0x330 fs/proc/inode.c:342
 vfs_write+0x24c/0x1150 fs/read_write.c:677
 ksys_write+0x12b/0x250 fs/read_write.c:731
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0xcd/0x250 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

The buggy address belongs to the object at ffff88807c2dba60
 which belongs to the cache kmalloc-16 of size 16
The buggy address is located 0 bytes to the right of
 allocated 16-byte region [ffff88807c2dba60, ffff88807c2dba70)

The buggy address belongs to the physical page:
page: refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x7c2db
flags: 0xfff00000000000(node=0|zone=1|lastcpupid=0x7ff)
page_type: f5(slab)
raw: 00fff00000000000 ffff88801ac41640 dead000000000122 0000000000000000
raw: 0000000000000000 0000000080800080 00000001f5000000 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 0xd2c40(GFP_NOFS|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC), pid 5817, tgid 5817 (syz-executor), ts 73841243093, free_ts 73725001247
 create_dummy_stack mm/page_owner.c:94 [inline]
 register_dummy_stack+0x8a/0xd0 mm/page_owner.c:100
 init_page_owner+0x48/0xe40 mm/page_owner.c:118
 invoke_init_callbacks mm/page_ext.c:148 [inline]
 page_ext_init+0x6b8/0xab0 mm/page_ext.c:497
 mm_core_init+0x12d/0x220 mm/mm_init.c:2669
page last free pid 90 tgid 90 stack trace:
 reset_page_owner include/linux/page_owner.h:25 [inline]
 free_pages_prepare mm/page_alloc.c:1127 [inline]
 free_unref_page+0x661/0x1080 mm/page_alloc.c:2657
 qlink_free mm/kasan/quarantine.c:163 [inline]
 qlist_free_all+0x4e/0x120 mm/kasan/quarantine.c:179
 kasan_quarantine_reduce+0x195/0x1e0 mm/kasan/quarantine.c:286
 __kasan_slab_alloc+0x69/0x90 mm/kasan/common.c:329
 kasan_slab_alloc include/linux/kasan.h:250 [inline]
 slab_post_alloc_hook mm/slub.c:4119 [inline]
 slab_alloc_node mm/slub.c:4168 [inline]
 kmem_cache_alloc_node_noprof+0x1ca/0x3b0 mm/slub.c:4220
 __alloc_skb+0x2b3/0x380 net/core/skbuff.c:668
 alloc_skb include/linux/skbuff.h:1323 [inline]
 alloc_skb_with_frags+0xe4/0x850 net/core/skbuff.c:6612
 sock_alloc_send_pskb+0x7f1/0x980 net/core/sock.c:2881
 sock_alloc_send_skb include/net/sock.h:1797 [inline]
 mld_newpack.isra.0+0x1d4/0x820 net/ipv6/mcast.c:1747
 add_grhead+0x299/0x340 net/ipv6/mcast.c:1850
 add_grec+0x111e/0x1670 net/ipv6/mcast.c:1988
 mld_send_initial_cr.part.0+0xe2/0x260 net/ipv6/mcast.c:2234
 mld_send_initial_cr net/ipv6/mcast.c:2225 [inline]
 mld_dad_work+0x51/0x2d0 net/ipv6/mcast.c:2260
 process_one_work+0x958/0x1b30 kernel/workqueue.c:3229
 process_scheduled_works kernel/workqueue.c:3310 [inline]
 worker_thread+0x6c8/0xf00 kernel/workqueue.c:3391
 kthread+0x2c1/0x3a0 kernel/kthread.c:389

Memory state around the buggy address:
 ffff88807c2db900: fa fb fc fc fa fb fc fc fa fb fc fc 00 00 fc fc
 ffff88807c2db980: fa fb fc fc 00 00 fc fc 00 06 fc fc 00 00 fc fc
>ffff88807c2dba00: 00 00 fc fc fa fb fc fc 00 00 fc fc 00 00 fc fc
                                                             ^
 ffff88807c2dba80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
 ffff88807c2dbb00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
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