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BUG: KASAN: slab-use-after-free in memcmp lib/string.c:676 [inline]
BUG: KASAN: slab-use-after-free in bcmp+0xc0/0x1e0 lib/string.c:708
Read of size 8 at addr ffff8880618de028 by task syz.0.477/11471

CPU: 0 UID: 0 PID: 11471 Comm: syz.0.477 Not tainted 6.14.0-rc4-syzkaller-00242-g7a5668899f54 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2025
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:94 [inline]
 dump_stack_lvl+0x241/0x360 lib/dump_stack.c:120
 print_address_description mm/kasan/report.c:408 [inline]
 print_report+0x16e/0x5b0 mm/kasan/report.c:521
 kasan_report+0x143/0x180 mm/kasan/report.c:634
 memcmp lib/string.c:676 [inline]
 bcmp+0xc0/0x1e0 lib/string.c:708
 _Z6memcmpPKvU25pass_dynamic_object_size0S0_U25pass_dynamic_object_size0m include/linux/fortify-string.h:727 [inline]
 __bch2_uuid_to_fs fs/bcachefs/super.c:221 [inline]
 bch2_fs_online+0x20b/0x860 fs/bcachefs/super.c:701
 bch2_fs_alloc fs/bcachefs/super.c:955 [inline]
 bch2_fs_open+0x3175/0x31e0 fs/bcachefs/super.c:2064
 bch2_fs_get_tree+0x738/0x17a0 fs/bcachefs/fs.c:2190
 vfs_get_tree+0x90/0x2b0 fs/super.c:1814
 do_new_mount+0x2be/0xb40 fs/namespace.c:3560
 do_mount fs/namespace.c:3900 [inline]
 __do_sys_mount fs/namespace.c:4111 [inline]
 __se_sys_mount+0x2d6/0x3c0 fs/namespace.c:4088
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0xf3/0x230 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7fb37ad8e90a
Code: d8 64 89 02 48 c7 c0 ff ff ff ff eb a6 e8 de 1a 00 00 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 49 89 ca b8 a5 00 00 00 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:00007fb37bb9de68 EFLAGS: 00000246 ORIG_RAX: 00000000000000a5
RAX: ffffffffffffffda RBX: 00007fb37bb9def0 RCX: 00007fb37ad8e90a
RDX: 00004000000000c0 RSI: 0000400000000180 RDI: 00007fb37bb9deb0
RBP: 00004000000000c0 R08: 00007fb37bb9def0 R09: 0000000002210010
R10: 0000000002210010 R11: 0000000000000246 R12: 0000400000000180
R13: 00007fb37bb9deb0 R14: 0000000000005a21 R15: 0000400000000100
 </TASK>

Allocated by task 11453:
 kasan_save_stack mm/kasan/common.c:47 [inline]
 kasan_save_track+0x3f/0x80 mm/kasan/common.c:68
 poison_kmalloc_redzone mm/kasan/common.c:377 [inline]
 __kasan_kmalloc+0x98/0xb0 mm/kasan/common.c:394
 kasan_kmalloc include/linux/kasan.h:260 [inline]
 __do_kmalloc_node mm/slub.c:4294 [inline]
 __kmalloc_node_track_caller_noprof+0x28b/0x4c0 mm/slub.c:4313
 __do_krealloc mm/slub.c:4820 [inline]
 krealloc_noprof+0x10f/0x300 mm/slub.c:4873
 bch2_sb_realloc+0x2d2/0x660 fs/bcachefs/super-io.c:200
 __copy_super+0x546/0x920 fs/bcachefs/super-io.c:631
 bch2_sb_to_fs+0xab/0x150 fs/bcachefs/super-io.c:658
 bch2_fs_alloc fs/bcachefs/super.c:834 [inline]
 bch2_fs_open+0x160f/0x31e0 fs/bcachefs/super.c:2064
 bch2_fs_get_tree+0x738/0x17a0 fs/bcachefs/fs.c:2190
 vfs_get_tree+0x90/0x2b0 fs/super.c:1814
 do_new_mount+0x2be/0xb40 fs/namespace.c:3560
 do_mount fs/namespace.c:3900 [inline]
 __do_sys_mount fs/namespace.c:4111 [inline]
 __se_sys_mount+0x2d6/0x3c0 fs/namespace.c:4088
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0xf3/0x230 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

The buggy address belongs to the object at ffff8880618de000
 which belongs to the cache kmalloc-4k of size 4096
The buggy address is located 40 bytes inside of
 freed 4096-byte region [ffff8880618de000, ffff8880618df000)

The buggy address belongs to the physical page:
page: refcount:0 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x618d8
head: order:3 mapcount:0 entire_mapcount:0 nr_pages_mapped:0 pincount:0
flags: 0xfff00000000040(head|node=0|zone=1|lastcpupid=0x7ff)
page_type: f5(slab)
raw: 00fff00000000040 ffff88801b042140 dead000000000122 0000000000000000
raw: 0000000000000000 0000000000040004 00000000f5000000 0000000000000000
head: 00fff00000000040 ffff88801b042140 dead000000000122 0000000000000000
head: 0000000000000000 0000000000040004 00000000f5000000 0000000000000000
head: 00fff00000000003 ffffea0001863601 ffffffffffffffff 0000000000000000
head: 0000000000000008 0000000000000000 00000000ffffffff 0000000000000000
page dumped because: kasan: bad access detected
page_owner tracks the page as allocated
page last allocated via order 3, migratetype Unmovable, gfp_mask 0xd2040(__GFP_IO|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC), pid 11453, tgid 11451 (syz.2.471), ts 384887593969, free_ts 384512891791
 set_page_owner include/linux/page_owner.h:32 [inline]
 post_alloc_hook+0x1f4/0x240 mm/page_alloc.c:1551
 prep_new_page mm/page_alloc.c:1559 [inline]
 get_page_from_freelist+0x3651/0x37a0 mm/page_alloc.c:3477
 __alloc_frozen_pages_noprof+0x292/0x710 mm/page_alloc.c:4739
 alloc_pages_mpol+0x311/0x660 mm/mempolicy.c:2270
 alloc_slab_page mm/slub.c:2423 [inline]
 allocate_slab+0x8f/0x3a0 mm/slub.c:2587
 new_slab mm/slub.c:2640 [inline]
 ___slab_alloc+0xc27/0x14a0 mm/slub.c:3826
 __slab_alloc+0x58/0xa0 mm/slub.c:3916
 __slab_alloc_node mm/slub.c:3991 [inline]
 slab_alloc_node mm/slub.c:4152 [inline]
 __do_kmalloc_node mm/slub.c:4293 [inline]
 __kmalloc_noprof+0x2e6/0x4c0 mm/slub.c:4306
 kmalloc_noprof include/linux/slab.h:905 [inline]
 tomoyo_realpath_from_path+0xcf/0x5e0 security/tomoyo/realpath.c:251
 tomoyo_mount_acl security/tomoyo/mount.c:105 [inline]
 tomoyo_mount_permission+0x3bf/0xb80 security/tomoyo/mount.c:237
 security_sb_mount+0xe0/0x2f0 security/security.c:1570
 path_mount+0xb9/0xfa0 fs/namespace.c:3829
 do_mount fs/namespace.c:3900 [inline]
 __do_sys_mount fs/namespace.c:4111 [inline]
 __se_sys_mount+0x2d6/0x3c0 fs/namespace.c:4088
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0xf3/0x230 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
page last free pid 5198 tgid 5198 stack trace:
 reset_page_owner include/linux/page_owner.h:25 [inline]
 free_pages_prepare mm/page_alloc.c:1127 [inline]
 free_frozen_pages+0xe04/0x10e0 mm/page_alloc.c:2660
 __slab_free+0x2c2/0x380 mm/slub.c:4520
 qlink_free mm/kasan/quarantine.c:163 [inline]
 qlist_free_all+0x9a/0x140 mm/kasan/quarantine.c:179
 kasan_quarantine_reduce+0x14f/0x170 mm/kasan/quarantine.c:286
 __kasan_slab_alloc+0x23/0x80 mm/kasan/common.c:329
 kasan_slab_alloc include/linux/kasan.h:250 [inline]
 slab_post_alloc_hook mm/slub.c:4115 [inline]
 slab_alloc_node mm/slub.c:4164 [inline]
 __do_kmalloc_node mm/slub.c:4293 [inline]
 __kmalloc_noprof+0x236/0x4c0 mm/slub.c:4306
 kmalloc_noprof include/linux/slab.h:905 [inline]
 kernfs_fop_write_iter+0x15a/0x500 fs/kernfs/file.c:311
 new_sync_write fs/read_write.c:586 [inline]
 vfs_write+0xacf/0xd10 fs/read_write.c:679
 ksys_write+0x18f/0x2b0 fs/read_write.c:731
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0xf3/0x230 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

Memory state around the buggy address:
 ffff8880618ddf00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
 ffff8880618ddf80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>ffff8880618de000: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                                  ^
 ffff8880618de080: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff8880618de100: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
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