bcachefs (loop0): scanning for missing backpointers in 5/128 buckets
 done
bcachefs (loop0): reconstruct_snapshots... done
bcachefs (loop0): check_subvols... done
bcachefs (loop0): check_inodes... done
bcachefs (loop0): check_dirents...
bcachefs (loop0): key in missing inode, found keys:
  u64s 7 type dirent 4096:189491840996961599:U32_MAX len 0 ver 0: file0 -> 4098 type dir
  u64s 7 type dirent 4096:1896155912177158345:U32_MAX len 0 ver 0: file3 -> 536870913 type reg
  u64s 7 type dirent 4096:2695648408715017799:U32_MAX len 0 ver 0: file2 -> 536870913 type reg
  u64s 7 type dirent 4096:4330382808765833931:U32_MAX len 0 ver 0: file1 -> 536870912 type reg
  u64s 8 type dirent 4096:8130059955150870709:U32_MAX len 0 ver 0: lost+found -> 4097 type dir
  u64s 8 type dirent 4096:9097378837824744618:U32_MAX len 0 ver 0: file.cold -> 536870914 type reg
  , fixing
bcachefs (loop0): hash table key at wrong offset: should be at 7938137874084403768
  u64s 7 type dirent 4096:189491840996961599:U32_MAX len 0 ver 0: file0 -> 4098 type dir, fixing
bcachefs (loop0): hash table key at wrong offset: should be at 5336963285177257433
  u64s 7 type dirent 4096:1896155912177158345:U32_MAX len 0 ver 0: file3 -> 536870913 type reg, fixing
bcachefs (loop0): hash table key at wrong offset: should be at 563749873485228157
  u64s 7 type dirent 4096:2695648408715017799:U32_MAX len 0 ver 0: file2 -> 536870913 type reg, fixing
bcachefs (loop0): hash table key at wrong offset: should be at 4020311612149773300
  u64s 7 type dirent 4096:4330382808765833931:U32_MAX len 0 ver 0: file1 -> 536870912 type reg, fixing
bcachefs (loop0): dirent points to missing inode:
  u64s 7 type dirent 4096:5336963285177257433:U32_MAX len 0 ver 0: file3 -> 536870913 type reg, fixing
bcachefs (loop0): dirent points to missing inode:
  u64s 7 type dirent 4096:7938137874084403768:U32_MAX len 0 ver 0: file0 -> 4098 type dir, fixing
bcachefs (loop0): hash table key at wrong offset: should be at 7330734444286019632
  u64s 8 type dirent 4096:8130059955150870709:U32_MAX len 0 ver 0: lost+found -> 4097 type dir, fixing
bcachefs (loop0): hash table key at wrong offset: should be at 1544467070642760408
  u64s 8 type dirent 4096:9097378837824744618:U32_MAX len 0 ver 0: file.cold -> 536870914 type reg, fixing
bcachefs (loop0): fsck counted subdirectories wrong for inum 4096:4294967295: got 2 should be 1
bcachefs (loop0): directory with wrong i_nlink: got 0, should be 1
  (disconnected), fixing
bcachefs (loop0): key in missing inode, found keys:
  u64s 7 type dirent 4098:5675548428000973578:U32_MAX len 0 ver 0: file1 -> 4100 type lnk
  u64s 7 type dirent 4098:8977922886548783724:U32_MAX len 0 ver 0: file0 -> 4099 type reg
  , fixing
bcachefs (loop0): key in missing inode, found keys:
  u64s 7 type dirent 4098:8977922886548783724:U32_MAX len 0 ver 0: file0 -> 4099 type reg
  , fixing
bcachefs (loop0): check_dirents requires second pass
bcachefs (loop0): dirent points to missing inode:
  u64s 7 type dirent 4096:563749873485228157:U32_MAX len 0 ver 0: file2 -> 536870913 type reg, fixing
bcachefs (loop0): dirent points to missing inode:
  u64s 8 type dirent 4096:1544467070642760408:U32_MAX len 0 ver 0: file.cold -> 536870914 type reg, fixing
bcachefs (loop0): dirent points to missing inode:
  u64s 7 type dirent 4096:4020311612149773300:U32_MAX len 0 ver 0: file1 -> 536870912 type reg, fixing
bcachefs (loop0): dirent points to missing inode:
  u64s 8 type dirent 4096:7330734444286019632:U32_MAX len 0 ver 0: lost+found -> 4097 type dir, fixing
==================================================================
BUG: KASAN: use-after-free in check_dirent fs/bcachefs/fsck.c:2418 [inline]
BUG: KASAN: use-after-free in bch2_check_dirents+0x1fac/0x33f0 fs/bcachefs/fsck.c:2444
Read of size 1 at addr ffff888056040140 by task syz.0.0/5334

CPU: 0 UID: 0 PID: 5334 Comm: syz.0.0 Not tainted 6.16.0-rc4-syzkaller-00013-g66701750d556 #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:408 [inline]
 print_report+0xd2/0x2b0 mm/kasan/report.c:521
 kasan_report+0x118/0x150 mm/kasan/report.c:634
 check_dirent fs/bcachefs/fsck.c:2418 [inline]
 bch2_check_dirents+0x1fac/0x33f0 fs/bcachefs/fsck.c:2444
 bch2_run_recovery_pass fs/bcachefs/recovery_passes.c:484 [inline]
 __bch2_run_recovery_passes+0x392/0x1010 fs/bcachefs/recovery_passes.c:539
 bch2_run_recovery_passes+0x184/0x210 fs/bcachefs/recovery_passes.c:610
 bch2_fs_recovery+0x2690/0x3a50 fs/bcachefs/recovery.c:1005
 bch2_fs_start+0xa99/0xd90 fs/bcachefs/super.c:1212
 bch2_fs_get_tree+0xafc/0x14f0 fs/bcachefs/fs.c:2490
 vfs_get_tree+0x92/0x2b0 fs/super.c:1804
 do_new_mount+0x24a/0xa40 fs/namespace.c:3902
 do_mount fs/namespace.c:4239 [inline]
 __do_sys_mount fs/namespace.c:4450 [inline]
 __se_sys_mount+0x317/0x410 fs/namespace.c:4427
 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: 0033:0x7f0b64b900ca
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:00007f0b65a4ae68 EFLAGS: 00000246 ORIG_RAX: 00000000000000a5
RAX: ffffffffffffffda RBX: 00007f0b65a4aef0 RCX: 00007f0b64b900ca
RDX: 00002000000000c0 RSI: 0000200000000080 RDI: 00007f0b65a4aeb0
RBP: 00002000000000c0 R08: 00007f0b65a4aef0 R09: 0000000000818001
R10: 0000000000818001 R11: 0000000000000246 R12: 0000200000000080
R13: 00007f0b65a4aeb0 R14: 0000000000005978 R15: 0000200000000480
 </TASK>

The buggy address belongs to the physical page:
page: refcount:0 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x56040
flags: 0x4fff00000000000(node=1|zone=1|lastcpupid=0x7ff)
page_type: f0(buddy)
raw: 04fff00000000000 ffff88805ffd6f08 ffff88805ffd6f08 0000000000000000
raw: 0000000000000000 0000000000000005 00000000f0000000 0000000000000000
page dumped because: kasan: bad access detected
page_owner tracks the page as freed
page last allocated via order 5, migratetype Unmovable, gfp_mask 0x42800(GFP_NOWAIT|__GFP_COMP), pid 5334, tgid 5333 (syz.0.0), ts 88148122308, free_ts 88248104397
 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_noprof+0xa/0x30 mm/page_alloc.c:4993
 __alloc_pages_node_noprof include/linux/gfp.h:284 [inline]
 alloc_pages_node_noprof include/linux/gfp.h:311 [inline]
 ___kmalloc_large_node+0x85/0x210 mm/slub.c:4272
 __kmalloc_large_node_noprof+0x18/0x90 mm/slub.c:4300
 __do_kmalloc_node mm/slub.c:4316 [inline]
 __kvmalloc_node_noprof+0x6d/0x5f0 mm/slub.c:5015
 btree_bounce_alloc fs/bcachefs/btree_io.c:127 [inline]
 btree_node_sort+0x666/0x1760 fs/bcachefs/btree_io.c:326
 bch2_btree_post_write_cleanup+0x11f/0xad0 fs/bcachefs/btree_io.c:2582
 bch2_btree_node_prep_for_write+0x337/0x650 fs/bcachefs/btree_trans_commit.c:95
 bch2_trans_lock_write+0x669/0xba0 fs/bcachefs/btree_trans_commit.c:131
 do_bch2_trans_commit fs/bcachefs/btree_trans_commit.c:850 [inline]
 __bch2_trans_commit+0x2773/0x8870 fs/bcachefs/btree_trans_commit.c:1085
 bch2_trans_commit fs/bcachefs/btree_update.h:241 [inline]
 bch2_check_dirents+0x811/0x33f0 fs/bcachefs/fsck.c:2444
 bch2_run_recovery_pass fs/bcachefs/recovery_passes.c:484 [inline]
 __bch2_run_recovery_passes+0x392/0x1010 fs/bcachefs/recovery_passes.c:539
 bch2_run_recovery_passes+0x184/0x210 fs/bcachefs/recovery_passes.c:610
 bch2_fs_recovery+0x2690/0x3a50 fs/bcachefs/recovery.c:1005
page last free pid 5334 tgid 5333 stack trace:
 reset_page_owner include/linux/page_owner.h:25 [inline]
 free_pages_prepare mm/page_alloc.c:1248 [inline]
 __free_pages_ok+0xa44/0xc20 mm/page_alloc.c:1424
 __folio_put+0x21b/0x2c0 mm/swap.c:112
 folio_put include/linux/mm.h:1356 [inline]
 free_large_kmalloc+0x145/0x200 mm/slub.c:4768
 btree_bounce_free fs/bcachefs/btree_io.c:115 [inline]
 btree_node_sort+0x117f/0x1760 fs/bcachefs/btree_io.c:383
 bch2_btree_post_write_cleanup+0x11f/0xad0 fs/bcachefs/btree_io.c:2582
 bch2_btree_node_prep_for_write+0x337/0x650 fs/bcachefs/btree_trans_commit.c:95
 bch2_trans_lock_write+0x669/0xba0 fs/bcachefs/btree_trans_commit.c:131
 do_bch2_trans_commit fs/bcachefs/btree_trans_commit.c:850 [inline]
 __bch2_trans_commit+0x2773/0x8870 fs/bcachefs/btree_trans_commit.c:1085
 bch2_trans_commit fs/bcachefs/btree_update.h:241 [inline]
 check_dirent fs/bcachefs/fsck.c:2413 [inline]
 bch2_check_dirents+0x1c5c/0x33f0 fs/bcachefs/fsck.c:2444
 bch2_run_recovery_pass fs/bcachefs/recovery_passes.c:484 [inline]
 __bch2_run_recovery_passes+0x392/0x1010 fs/bcachefs/recovery_passes.c:539
 bch2_run_recovery_passes+0x184/0x210 fs/bcachefs/recovery_passes.c:610
 bch2_fs_recovery+0x2690/0x3a50 fs/bcachefs/recovery.c:1005
 bch2_fs_start+0xa99/0xd90 fs/bcachefs/super.c:1212
 bch2_fs_get_tree+0xafc/0x14f0 fs/bcachefs/fs.c:2490
 vfs_get_tree+0x92/0x2b0 fs/super.c:1804
 do_new_mount+0x24a/0xa40 fs/namespace.c:3902

Memory state around the buggy address:
 ffff888056040000: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff888056040080: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
>ffff888056040100: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
                                           ^
 ffff888056040180: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff888056040200: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
==================================================================