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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+0x13a9/0x15f0 fs/afs/addr_prefs.c:415
Read of size 1 at addr ffff88802a395f87 by task syz.0.5898/28066

CPU: 1 UID: 0 PID: 28066 Comm: syz.0.5898 Not tainted 6.15.0-rc6-syzkaller-00085-gc94d59a126cb #0 PREEMPT(full) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/07/2025
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:408 [inline]
 print_report+0xc3/0x670 mm/kasan/report.c:521
 kasan_report+0xe0/0x110 mm/kasan/report.c:634
 afs_split_string fs/afs/addr_prefs.c:51 [inline]
 afs_proc_addr_prefs_write+0x13a9/0x15f0 fs/afs/addr_prefs.c:415
 proc_simple_write+0x117/0x1b0 fs/proc/generic.c:825
 pde_write fs/proc/inode.c:330 [inline]
 proc_reg_write+0x23d/0x330 fs/proc/inode.c:342
 do_loop_readv_writev fs/read_write.c:848 [inline]
 do_loop_readv_writev fs/read_write.c:833 [inline]
 vfs_writev+0x6c7/0xdc0 fs/read_write.c:1057
 do_writev+0x132/0x330 fs/read_write.c:1101
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xcd/0x230 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f9a0358e969
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:00007f9a0437e038 EFLAGS: 00000246 ORIG_RAX: 0000000000000014
RAX: ffffffffffffffda RBX: 00007f9a037b6080 RCX: 00007f9a0358e969
RDX: 0000000000000003 RSI: 0000200000000040 RDI: 0000000000000003
RBP: 00007f9a03610ab1 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 0000000000000000 R14: 00007f9a037b6080 R15: 00007ffc2a894058
 </TASK>

Allocated by task 28066:
 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:4327 [inline]
 __kmalloc_node_track_caller_noprof+0x221/0x510 mm/slub.c:4346
 memdup_user_nul+0x2b/0x120 mm/util.c:302
 proc_simple_write+0xc7/0x1b0 fs/proc/generic.c:822
 pde_write fs/proc/inode.c:330 [inline]
 proc_reg_write+0x23d/0x330 fs/proc/inode.c:342
 do_loop_readv_writev fs/read_write.c:848 [inline]
 do_loop_readv_writev fs/read_write.c:833 [inline]
 vfs_writev+0x6c7/0xdc0 fs/read_write.c:1057
 do_writev+0x132/0x330 fs/read_write.c:1101
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xcd/0x230 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

The buggy address belongs to the object at ffff88802a395f80
 which belongs to the cache kmalloc-8 of size 8
The buggy address is located 0 bytes to the right of
 allocated 7-byte region [ffff88802a395f80, ffff88802a395f87)

The buggy address belongs to the physical page:
page: refcount:0 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x2a395
anon flags: 0xfff00000000000(node=0|zone=1|lastcpupid=0x7ff)
page_type: f5(slab)
raw: 00fff00000000000 ffff88801b441500 0000000000000000 dead000000000001
raw: 0000000000000000 0000000080800080 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 0x52cc0(GFP_KERNEL|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP), pid 6072, tgid 6071 (syz.0.33), ts 110508446144, free_ts 107624650748
 set_page_owner include/linux/page_owner.h:32 [inline]
 post_alloc_hook+0x181/0x1b0 mm/page_alloc.c:1718
 prep_new_page mm/page_alloc.c:1726 [inline]
 get_page_from_freelist+0x135c/0x3920 mm/page_alloc.c:3688
 __alloc_frozen_pages_noprof+0x263/0x23a0 mm/page_alloc.c:4970
 alloc_pages_mpol+0x1fb/0x550 mm/mempolicy.c:2301
 alloc_slab_page mm/slub.c:2450 [inline]
 allocate_slab mm/slub.c:2618 [inline]
 new_slab+0x244/0x340 mm/slub.c:2672
 ___slab_alloc+0xd9c/0x1940 mm/slub.c:3858
 __slab_alloc.constprop.0+0x56/0xb0 mm/slub.c:3948
 __slab_alloc_node mm/slub.c:4023 [inline]
 slab_alloc_node mm/slub.c:4184 [inline]
 __do_kmalloc_node mm/slub.c:4326 [inline]
 __kmalloc_node_track_caller_noprof+0x2ee/0x510 mm/slub.c:4346
 __kmemdup_nul mm/util.c:63 [inline]
 kstrdup+0x53/0x100 mm/util.c:83
 kstrdup_const+0x63/0x80 mm/util.c:103
 __kernfs_new_node+0x9b/0x8a0 fs/kernfs/dir.c:633
 kernfs_new_node+0x13c/0x1e0 fs/kernfs/dir.c:713
 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_add_class_symlinks drivers/base/core.c:3451 [inline]
 device_add+0x62c/0x1a70 drivers/base/core.c:3643
page last free pid 6044 tgid 6039 stack trace:
 reset_page_owner include/linux/page_owner.h:25 [inline]
 free_pages_prepare mm/page_alloc.c:1262 [inline]
 __free_frozen_pages+0x69d/0xff0 mm/page_alloc.c:2725
 vfree+0x176/0x960 mm/vmalloc.c:3384
 snd_dma_free_pages+0x54/0x70 sound/core/memalloc.c:132
 do_free_pages sound/core/pcm_memory.c:88 [inline]
 do_free_pages sound/core/pcm_memory.c:83 [inline]
 snd_pcm_lib_free_pages+0x172/0x390 sound/core/pcm_memory.c:495
 do_hw_free sound/core/pcm_native.c:894 [inline]
 snd_pcm_release_substream.part.0+0x2a8/0x340 sound/core/pcm_native.c:2718
 snd_pcm_release_substream+0x5b/0x70 sound/core/pcm_native.c:2712
 snd_pcm_oss_release_file sound/core/oss/pcm_oss.c:2398 [inline]
 snd_pcm_oss_release_file sound/core/oss/pcm_oss.c:2390 [inline]
 snd_pcm_oss_release+0x16f/0x310 sound/core/oss/pcm_oss.c:2577
 __fput+0x3ff/0xb70 fs/file_table.c:465
 task_work_run+0x14d/0x240 kernel/task_work.c:227
 resume_user_mode_work include/linux/resume_user_mode.h:50 [inline]
 exit_to_user_mode_loop kernel/entry/common.c:114 [inline]
 exit_to_user_mode_prepare include/linux/entry-common.h:329 [inline]
 __syscall_exit_to_user_mode_work kernel/entry/common.c:207 [inline]
 syscall_exit_to_user_mode+0x27b/0x2a0 kernel/entry/common.c:218
 do_syscall_64+0xda/0x230 arch/x86/entry/syscall_64.c:100
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

Memory state around the buggy address:
 ffff88802a395e80: 06 fc fc fc 05 fc fc fc 06 fc fc fc 05 fc fc fc
 ffff88802a395f00: 06 fc fc fc fa fc fc fc 06 fc fc fc 05 fc fc fc
>ffff88802a395f80: 07 fc fc fc 00 fc fc fc 05 fc fc fc fa fc fc fc
                   ^
 ffff88802a396000: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
 ffff88802a396080: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
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