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BUG: KASAN: slab-out-of-bounds in bch2_dirent_init_name+0x396/0x8b0 fs/bcachefs/dirent.c:276
Write of size 1985 at addr ffff88803b131233 by task syz.7.102/7086

CPU: 1 UID: 0 PID: 7086 Comm: syz.7.102 Tainted: G        W           6.16.0-syzkaller-06699-ge8d780dcd957 #0 PREEMPT_{RT,(full)} 
Tainted: [W]=WARN
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/12/2025
Call Trace:
 <TASK>
 dump_stack_lvl+0x189/0x250 lib/dump_stack.c:120
 print_address_description mm/kasan/report.c:378 [inline]
 print_report+0xca/0x240 mm/kasan/report.c:482
 kasan_report+0x118/0x150 mm/kasan/report.c:595
 check_region_inline mm/kasan/generic.c:-1 [inline]
 kasan_check_range+0x2b0/0x2c0 mm/kasan/generic.c:189
 __asan_memset+0x22/0x50 mm/kasan/shadow.c:84
 bch2_dirent_init_name+0x396/0x8b0 fs/bcachefs/dirent.c:276
 bch2_dirent_create_key+0x2a1/0x5f0 fs/bcachefs/dirent.c:319
 bch2_dirent_create+0xc5/0xc80 fs/bcachefs/dirent.c:362
 bch2_link_trans+0x39e/0x560 fs/bcachefs/namei.c:241
 __bch2_link+0x231/0x3f0 fs/bcachefs/fs.c:776
 bch2_symlink+0x183/0x240 fs/bcachefs/fs.c:892
 vfs_symlink+0x140/0x2f0 fs/namei.c:4730
 do_symlinkat+0x1b1/0x3f0 fs/namei.c:4756
 __do_sys_symlink fs/namei.c:4777 [inline]
 __se_sys_symlink fs/namei.c:4775 [inline]
 __x64_sys_symlink+0x7a/0x90 fs/namei.c:4775
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xfa/0x3b0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7fbdee57e9a9
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:00007fbdec3de038 EFLAGS: 00000246 ORIG_RAX: 0000000000000058
RAX: ffffffffffffffda RBX: 00007fbdee7a5fa0 RCX: 00007fbdee57e9a9
RDX: 0000000000000000 RSI: 00002000000001c0 RDI: 0000200000000300
RBP: 00007fbdee600d69 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 0000000000000000 R14: 00007fbdee7a5fa0 R15: 00007ffea9db2f68
 </TASK>

Allocated by task 7086:
 kasan_save_stack mm/kasan/common.c:47 [inline]
 kasan_save_track+0x3e/0x80 mm/kasan/common.c:68
 poison_kmalloc_redzone mm/kasan/common.c:377 [inline]
 __kasan_kmalloc+0x93/0xb0 mm/kasan/common.c:394
 kasan_kmalloc include/linux/kasan.h:260 [inline]
 __do_kmalloc_node mm/slub.c:4364 [inline]
 __kmalloc_noprof+0x1ef/0x430 mm/slub.c:4376
 kmalloc_noprof include/linux/slab.h:909 [inline]
 __bch2_trans_kmalloc+0x395/0x9d0 fs/bcachefs/btree_iter.c:3242
 bch2_trans_kmalloc_ip fs/bcachefs/btree_iter.h:604 [inline]
 bch2_trans_kmalloc fs/bcachefs/btree_iter.h:616 [inline]
 bch2_dirent_create_key+0x113/0x5f0 fs/bcachefs/dirent.c:302
 bch2_dirent_create+0xc5/0xc80 fs/bcachefs/dirent.c:362
 bch2_link_trans+0x39e/0x560 fs/bcachefs/namei.c:241
 __bch2_link+0x231/0x3f0 fs/bcachefs/fs.c:776
 bch2_symlink+0x183/0x240 fs/bcachefs/fs.c:892
 vfs_symlink+0x140/0x2f0 fs/namei.c:4730
 do_symlinkat+0x1b1/0x3f0 fs/namei.c:4756
 __do_sys_symlink fs/namei.c:4777 [inline]
 __se_sys_symlink fs/namei.c:4775 [inline]
 __x64_sys_symlink+0x7a/0x90 fs/namei.c:4775
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xfa/0x3b0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

The buggy address belongs to the object at ffff88803b131000
 which belongs to the cache kmalloc-2k of size 2048
The buggy address is located 563 bytes inside of
 allocated 2048-byte region [ffff88803b131000, ffff88803b131800)

The buggy address belongs to the physical page:
page: refcount:0 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x3b130
head: order:3 mapcount:0 entire_mapcount:0 nr_pages_mapped:0 pincount:0
anon flags: 0x80000000000040(head|node=0|zone=1)
page_type: f5(slab)
raw: 0080000000000040 ffff888019842000 0000000000000000 dead000000000001
raw: 0000000000000000 0000000080080008 00000000f5000000 0000000000000000
head: 0080000000000040 ffff888019842000 0000000000000000 dead000000000001
head: 0000000000000000 0000000080080008 00000000f5000000 0000000000000000
head: 0080000000000003 ffffea0000ec4c01 00000000ffffffff 00000000ffffffff
head: 0000000000000000 0000000000000000 00000000ffffffff 0000000000000008
page dumped because: kasan: bad access detected
page_owner tracks the page as allocated
page last allocated via order 3, migratetype Unmovable, gfp_mask 0xd20c0(__GFP_IO|__GFP_FS|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC), pid 1309, tgid 1309 (kworker/u8:7), ts 100693579964, free_ts 100665694817
 set_page_owner include/linux/page_owner.h:32 [inline]
 post_alloc_hook+0x240/0x2a0 mm/page_alloc.c:1704
 prep_new_page mm/page_alloc.c:1712 [inline]
 get_page_from_freelist+0x2119/0x21b0 mm/page_alloc.c:3669
 __alloc_frozen_pages_noprof+0x181/0x370 mm/page_alloc.c:4959
 alloc_pages_mpol+0xd1/0x380 mm/mempolicy.c:2419
 alloc_slab_page mm/slub.c:2486 [inline]
 allocate_slab+0x8a/0x370 mm/slub.c:2654
 new_slab mm/slub.c:2708 [inline]
 ___slab_alloc+0x8d1/0xdd0 mm/slub.c:3890
 __slab_alloc mm/slub.c:3980 [inline]
 __slab_alloc_node mm/slub.c:4055 [inline]
 slab_alloc_node mm/slub.c:4216 [inline]
 __do_kmalloc_node mm/slub.c:4363 [inline]
 __kmalloc_noprof+0x145/0x430 mm/slub.c:4376
 kmalloc_noprof include/linux/slab.h:909 [inline]
 __bch2_trans_get+0x710/0xd80 fs/bcachefs/btree_iter.c:3497
 btree_update_nodes_written fs/bcachefs/btree_update_interior.c:666 [inline]
 btree_interior_update_work+0x1fa/0x27d0 fs/bcachefs/btree_update_interior.c:867
 process_one_work kernel/workqueue.c:3238 [inline]
 process_scheduled_works+0xade/0x17b0 kernel/workqueue.c:3321
 worker_thread+0x8a0/0xda0 kernel/workqueue.c:3402
 kthread+0x70e/0x8a0 kernel/kthread.c:464
 ret_from_fork+0x3fc/0x770 arch/x86/kernel/process.c:148
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
page last free pid 5813 tgid 5813 stack trace:
 reset_page_owner include/linux/page_owner.h:25 [inline]
 free_pages_prepare mm/page_alloc.c:1248 [inline]
 __free_frozen_pages+0xbe5/0xdf0 mm/page_alloc.c:2706
 __slab_free+0x2db/0x390 mm/slub.c:4590
 qlink_free mm/kasan/quarantine.c:163 [inline]
 qlist_free_all+0x97/0x140 mm/kasan/quarantine.c:179
 kasan_quarantine_reduce+0x148/0x160 mm/kasan/quarantine.c:286
 __kasan_slab_alloc+0x22/0x80 mm/kasan/common.c:329
 kasan_slab_alloc include/linux/kasan.h:250 [inline]
 slab_post_alloc_hook mm/slub.c:4179 [inline]
 slab_alloc_node mm/slub.c:4228 [inline]
 __kmalloc_cache_noprof+0x143/0x320 mm/slub.c:4390
 kmalloc_noprof include/linux/slab.h:905 [inline]
 get_mountpoint+0x2cc/0x510 fs/namespace.c:953
 do_lock_mount+0x31b/0x590 fs/namespace.c:2818
 lock_mount fs/namespace.c:2841 [inline]
 do_loopback+0x27c/0x430 fs/namespace.c:3023
 do_mount fs/namespace.c:4133 [inline]
 __do_sys_mount fs/namespace.c:4344 [inline]
 __se_sys_mount+0x317/0x410 fs/namespace.c:4321
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xfa/0x3b0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

Memory state around the buggy address:
 ffff88803b131700: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
 ffff88803b131780: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
>ffff88803b131800: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
                   ^
 ffff88803b131880: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
 ffff88803b131900: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
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