syzbot

dirent points to missing inode:
u64s 8 type dirent 4096:8130059955150870709:U32_MAX len 0 ver 0: lost+found -> 4097 type dir, fixing
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BUG: KASAN: use-after-free in check_dirent fs/bcachefs/fsck.c:2528 [inline]
BUG: KASAN: use-after-free in bch2_check_dirents+0x1fee/0x2570 fs/bcachefs/fsck.c:2552
Read of size 1 at addr ffff88805da80160 by task syz-executor262/6243

CPU: 0 UID: 0 PID: 6243 Comm: syz-executor262 Not tainted 6.12.0-rc7-syzkaller-00125-gcfaaa7d010d1 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/30/2024
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:377 [inline]
 print_report+0x169/0x550 mm/kasan/report.c:488
 kasan_report+0x143/0x180 mm/kasan/report.c:601
 check_dirent fs/bcachefs/fsck.c:2528 [inline]
 bch2_check_dirents+0x1fee/0x2570 fs/bcachefs/fsck.c:2552
 bch2_run_recovery_pass+0xf0/0x1e0 fs/bcachefs/recovery_passes.c:191
 bch2_run_recovery_passes+0x3a7/0x880 fs/bcachefs/recovery_passes.c:244
 bch2_fs_recovery+0x25cc/0x39d0 fs/bcachefs/recovery.c:861
 bch2_fs_start+0x356/0x5b0 fs/bcachefs/super.c:1037
 bch2_fs_get_tree+0xd68/0x1710 fs/bcachefs/fs.c:2170
 vfs_get_tree+0x90/0x2b0 fs/super.c:1814
 do_new_mount+0x2be/0xb40 fs/namespace.c:3507
 do_mount fs/namespace.c:3847 [inline]
 __do_sys_mount fs/namespace.c:4057 [inline]
 __se_sys_mount+0x2d6/0x3c0 fs/namespace.c:4034
 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: 0033:0x7f669fe0863a
Code: d8 64 89 02 48 c7 c0 ff ff ff ff eb a6 e8 7e 09 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 b0 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f669fdaefd8 EFLAGS: 00000282 ORIG_RAX: 00000000000000a5
RAX: ffffffffffffffda RBX: 00007f669fdaeff0 RCX: 00007f669fe0863a
RDX: 00000000200058c0 RSI: 0000000020000000 RDI: 00007f669fdaeff0
RBP: 0000000000000004 R08: 00007f669fdaf030 R09: 0000000000005917
R10: 0000000000010000 R11: 0000000000000282 R12: 00007f669fdaf030
R13: 0000000000010000 R14: 0000000000000003 R15: 0000000001000000
 </TASK>

The buggy address belongs to the physical page:
page: refcount:0 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x5da80
flags: 0xfff00000000000(node=0|zone=1|lastcpupid=0x7ff)
page_type: f0(buddy)
raw: 00fff00000000000 ffff88813fffc788 ffffea00015da808 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 0x52800(GFP_NOWAIT|__GFP_NORETRY|__GFP_COMP), pid 6243, tgid 6242 (syz-executor262), ts 88543202500, free_ts 96575602066
 set_page_owner include/linux/page_owner.h:32 [inline]
 post_alloc_hook+0x1f3/0x230 mm/page_alloc.c:1556
 prep_new_page mm/page_alloc.c:1564 [inline]
 get_page_from_freelist+0x363e/0x3790 mm/page_alloc.c:3474
 __alloc_pages_noprof+0x292/0x710 mm/page_alloc.c:4750
 __alloc_pages_node_noprof include/linux/gfp.h:269 [inline]
 alloc_pages_node_noprof include/linux/gfp.h:296 [inline]
 ___kmalloc_large_node+0x8b/0x1d0 mm/slub.c:4209
 __kmalloc_large_node_noprof+0x1a/0x80 mm/slub.c:4236
 __do_kmalloc_node mm/slub.c:4252 [inline]
 __kmalloc_node_noprof+0x2d2/0x440 mm/slub.c:4270
 __kvmalloc_node_noprof+0x72/0x190 mm/util.c:658
 btree_bounce_alloc fs/bcachefs/btree_io.c:124 [inline]
 bch2_btree_node_read_done+0x3808/0x5e90 fs/bcachefs/btree_io.c:1188
 btree_node_read_work+0x68b/0x1260 fs/bcachefs/btree_io.c:1323
 bch2_btree_node_read+0x2433/0x2a10
 __bch2_btree_root_read fs/bcachefs/btree_io.c:1749 [inline]
 bch2_btree_root_read+0x617/0x7a0 fs/bcachefs/btree_io.c:1771
 read_btree_roots+0x296/0x840 fs/bcachefs/recovery.c:523
 bch2_fs_recovery+0x2585/0x39d0 fs/bcachefs/recovery.c:853
 bch2_fs_start+0x356/0x5b0 fs/bcachefs/super.c:1037
 bch2_fs_get_tree+0xd68/0x1710 fs/bcachefs/fs.c:2170
 vfs_get_tree+0x90/0x2b0 fs/super.c:1814
page last free pid 6243 tgid 6242 stack trace:
 reset_page_owner include/linux/page_owner.h:25 [inline]
 free_pages_prepare mm/page_alloc.c:1127 [inline]
 __free_pages_ok+0xc91/0xf90 mm/page_alloc.c:1269
 __folio_put+0x2c7/0x440 mm/swap.c:112
 folio_put include/linux/mm.h:1478 [inline]
 free_large_kmalloc+0x105/0x1c0 mm/slub.c:4698
 kfree+0x21c/0x440 mm/slub.c:4721
 btree_bounce_free fs/bcachefs/btree_io.c:112 [inline]
 btree_node_sort+0x1100/0x1830 fs/bcachefs/btree_io.c:380
 bch2_btree_post_write_cleanup+0x11a/0xa70 fs/bcachefs/btree_io.c:2248
 bch2_btree_node_prep_for_write+0x55b/0x8f0 fs/bcachefs/btree_trans_commit.c:93
 bch2_trans_lock_write+0x68e/0xc60 fs/bcachefs/btree_trans_commit.c:129
 do_bch2_trans_commit fs/bcachefs/btree_trans_commit.c:896 [inline]
 __bch2_trans_commit+0x26f2/0x93c0 fs/bcachefs/btree_trans_commit.c:1121
 bch2_trans_commit fs/bcachefs/btree_update.h:184 [inline]
 check_dirent fs/bcachefs/fsck.c:2524 [inline]
 bch2_check_dirents+0x1431/0x2570 fs/bcachefs/fsck.c:2552
 bch2_run_recovery_pass+0xf0/0x1e0 fs/bcachefs/recovery_passes.c:191
 bch2_run_recovery_passes+0x3a7/0x880 fs/bcachefs/recovery_passes.c:244
 bch2_fs_recovery+0x25cc/0x39d0 fs/bcachefs/recovery.c:861
 bch2_fs_start+0x356/0x5b0 fs/bcachefs/super.c:1037
 bch2_fs_get_tree+0xd68/0x1710 fs/bcachefs/fs.c:2170
 vfs_get_tree+0x90/0x2b0 fs/super.c:1814

Memory state around the buggy address:
 ffff88805da80000: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff88805da80080: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
>ffff88805da80100: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
                                                       ^
 ffff88805da80180: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff88805da80200: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
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