loop0: detected capacity change from 0 to 32768
bcachefs (loop0): starting version 1.7: mi_btree_bitmap opts=errors=continue,metadata_checksum=none,data_checksum=none,checksum_err_retry_nr=12,compression=lz4,foreground_target=invalid label 767,background_target=invalid device 7,degraded=yes,nojournal_transaction_names
  allowing incompatible features above 0.0: (unknown version)
  features: lz4,new_siphash,inline_data,new_extent_overwrite,btree_ptr_v2,new_varint,journal_no_flush,alloc_v2,extents_across_btree_nodes
bcachefs (loop0): Using encoding defined by superblock: utf8-12.1.0
bcachefs (loop0): initializing new filesystem
bcachefs (loop0): going read-write
bcachefs (loop0): marking superblocks
bcachefs (loop0): initializing freespace
bcachefs (loop0): done initializing freespace
bcachefs (loop0): reading snapshots table
bcachefs (loop0): reading snapshots done
bcachefs (loop0): done starting filesystem
==================================================================
BUG: KASAN: slab-out-of-bounds in bch2_dirent_init_name+0x396/0x8b0 fs/bcachefs/dirent.c:276
Write of size 1985 at addr ffff88805590f233 by task syz.0.0/5332

CPU: 0 UID: 0 PID: 5332 Comm: syz.0.0 Not tainted 6.16.0-syzkaller-04405-g4b290aae788e #0 PREEMPT(full) 
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2~bpo12+1 04/01/2014
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_link+0x197/0x220 fs/bcachefs/fs.c:805
 vfs_link+0x4ed/0x6e0 fs/namei.c:4854
 do_linkat+0x272/0x560 fs/namei.c:4924
 __do_sys_link fs/namei.c:4958 [inline]
 __se_sys_link fs/namei.c:4956 [inline]
 __x64_sys_link+0x82/0x90 fs/namei.c:4956
 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: 0033:0x7f5d0098e9a9
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:00007f5d017ee038 EFLAGS: 00000246 ORIG_RAX: 0000000000000056
RAX: ffffffffffffffda RBX: 00007f5d00bb5fa0 RCX: 00007f5d0098e9a9
RDX: 0000000000000000 RSI: 0000200000000bc0 RDI: 0000200000001240
RBP: 00007f5d00a10d69 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 0000000000000000 R14: 00007f5d00bb5fa0 R15: 00007ffc52d62b68
 </TASK>

Allocated by task 5332:
 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:4328 [inline]
 __kmalloc_noprof+0x27a/0x4f0 mm/slub.c:4340
 kmalloc_noprof include/linux/slab.h:909 [inline]
 __bch2_trans_kmalloc+0x396/0x9d0 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_link+0x197/0x220 fs/bcachefs/fs.c:805
 vfs_link+0x4ed/0x6e0 fs/namei.c:4854
 do_linkat+0x272/0x560 fs/namei.c:4924
 __do_sys_link fs/namei.c:4958 [inline]
 __se_sys_link fs/namei.c:4956 [inline]
 __x64_sys_link+0x82/0x90 fs/namei.c:4956
 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 ffff88805590f000
 which belongs to the cache kmalloc-2k of size 2048
The buggy address is located 563 bytes inside of
 allocated 2048-byte region [ffff88805590f000, ffff88805590f800)

The buggy address belongs to the physical page:
page: refcount:0 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x55908
head: order:3 mapcount:0 entire_mapcount:0 nr_pages_mapped:0 pincount:0
flags: 0x4fff00000000040(head|node=1|zone=1|lastcpupid=0x7ff)
page_type: f5(slab)
raw: 04fff00000000040 ffff88801a442000 dead000000000122 0000000000000000
raw: 0000000000000000 0000000080080008 00000000f5000000 0000000000000000
head: 04fff00000000040 ffff88801a442000 dead000000000122 0000000000000000
head: 0000000000000000 0000000080080008 00000000f5000000 0000000000000000
head: 04fff00000000003 ffffea0001564201 00000000ffffffff 00000000ffffffff
head: ffffffffffffffff 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 0xd2040(__GFP_IO|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC), pid 5332, tgid 5331 (syz.0.0), ts 76023490974, free_ts 0
 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+0x21e4/0x22c0 mm/page_alloc.c:3669
 __alloc_frozen_pages_noprof+0x181/0x370 mm/page_alloc.c:4959
 alloc_pages_mpol+0x232/0x4a0 mm/mempolicy.c:2419
 alloc_slab_page mm/slub.c:2451 [inline]
 allocate_slab+0x8a/0x3b0 mm/slub.c:2619
 new_slab mm/slub.c:2673 [inline]
 ___slab_alloc+0xbfc/0x1480 mm/slub.c:3859
 __slab_alloc mm/slub.c:3949 [inline]
 __slab_alloc_node mm/slub.c:4024 [inline]
 slab_alloc_node mm/slub.c:4185 [inline]
 __do_kmalloc_node mm/slub.c:4327 [inline]
 __kmalloc_node_track_caller_noprof+0x2f8/0x4e0 mm/slub.c:4347
 __do_krealloc mm/slub.c:4905 [inline]
 krealloc_noprof+0x124/0x340 mm/slub.c:4958
 bch2_printbuf_make_room+0x1f5/0x360 fs/bcachefs/printbuf.c:59
 bch2_prt_printf+0x282/0x740 fs/bcachefs/printbuf.c:186
 bch2_btree_path_to_text_short+0x148/0xde0 fs/bcachefs/btree_iter.c:1516
 __bch2_trans_paths_to_text+0xe5/0x190 fs/bcachefs/btree_iter.c:1589
 bch2_trans_update_max_paths+0x14e/0x340 fs/bcachefs/btree_iter.c:1625
 btree_path_alloc+0x89a/0xa70 fs/bcachefs/btree_iter.c:1722
 bch2_path_get+0x8bd/0x1540 fs/bcachefs/btree_iter.c:1778
 bch2_trans_iter_init_common fs/bcachefs/btree_iter.h:529 [inline]
 bch2_trans_iter_init_outlined+0x265/0x400 fs/bcachefs/btree_iter.c:3126
page_owner free stack trace missing

Memory state around the buggy address:
 ffff88805590f700: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
 ffff88805590f780: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
>ffff88805590f800: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
                   ^
 ffff88805590f880: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
 ffff88805590f900: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
==================================================================