u64s 7 type dirent 4096:2695648408715017799:U32_MAX len 0 ver 0: file2 -> 536870913 type reg, fixing
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BUG: KASAN: use-after-free in check_dirent fs/bcachefs/fsck.c:2395 [inline]
BUG: KASAN: use-after-free in bch2_check_dirents+0x1fac/0x33f0 fs/bcachefs/fsck.c:2421
Read of size 1 at addr ffff888048920110 by task syz.6.1512/10720

CPU: 0 UID: 0 PID: 10720 Comm: syz.6.1512 Not tainted 6.16.0-rc5-syzkaller-00276-g5d5d62298b8b #0 PREEMPT(full) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/07/2025
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/0x230 mm/kasan/report.c:480
 kasan_report+0x118/0x150 mm/kasan/report.c:593
 check_dirent fs/bcachefs/fsck.c:2395 [inline]
 bch2_check_dirents+0x1fac/0x33f0 fs/bcachefs/fsck.c:2421
 bch2_run_recovery_pass fs/bcachefs/recovery_passes.c:484 [inline]
 __bch2_run_recovery_passes+0x395/0x1010 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:1016
 bch2_fs_start+0xaaf/0xda0 fs/bcachefs/super.c:1213
 bch2_fs_get_tree+0xb39/0x1520 fs/bcachefs/fs.c:2488
 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: 0033:0x7f6f6bf900ca
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:00007f6f6cd8fe68 EFLAGS: 00000246 ORIG_RAX: 00000000000000a5
RAX: ffffffffffffffda RBX: 00007f6f6cd8fef0 RCX: 00007f6f6bf900ca
RDX: 0000200000000080 RSI: 00002000000000c0 RDI: 00007f6f6cd8feb0
RBP: 0000200000000080 R08: 00007f6f6cd8fef0 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00002000000000c0
R13: 00007f6f6cd8feb0 R14: 000000000000596f R15: 0000200000000040
 </TASK>

The buggy address belongs to the physical page:
page: refcount:0 mapcount:0 mapping:0000000000000000 index:0x3ff2 pfn:0x48920
flags: 0xfff00000000000(node=0|zone=1|lastcpupid=0x7ff)
page_type: f0(buddy)
raw: 00fff00000000000 ffffea0001209808 ffff88813fffbf08 0000000000000000
raw: 0000000000003ff2 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 10720, tgid 10719 (syz.6.1512), ts 500891016120, free_ts 505996226909
 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]
 bch2_btree_node_read_done+0x3305/0x5520 fs/bcachefs/btree_io.c:1278
 btree_node_read_work+0x40e/0xe60 fs/bcachefs/btree_io.c:1440
 bch2_btree_node_read+0x887/0x2a00 fs/bcachefs/btree_io.c:-1
 __bch2_btree_root_read fs/bcachefs/btree_io.c:1906 [inline]
 bch2_btree_root_read+0x5f0/0x760 fs/bcachefs/btree_io.c:1928
 read_btree_roots+0x2c6/0x840 fs/bcachefs/recovery.c:615
 bch2_fs_recovery+0x261f/0x3a50 fs/bcachefs/recovery.c:1006
 bch2_fs_start+0xaaf/0xda0 fs/bcachefs/super.c:1213
 bch2_fs_get_tree+0xb39/0x1520 fs/bcachefs/fs.c:2488
 vfs_get_tree+0x92/0x2b0 fs/super.c:1804
page last free pid 10720 tgid 10719 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:2607
 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:2390 [inline]
 bch2_check_dirents+0x1c5c/0x33f0 fs/bcachefs/fsck.c:2421
 bch2_run_recovery_pass fs/bcachefs/recovery_passes.c:484 [inline]
 __bch2_run_recovery_passes+0x395/0x1010 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:1016
 bch2_fs_start+0xaaf/0xda0 fs/bcachefs/super.c:1213
 bch2_fs_get_tree+0xb39/0x1520 fs/bcachefs/fs.c:2488
 vfs_get_tree+0x92/0x2b0 fs/super.c:1804
 do_new_mount+0x24a/0xa40 fs/namespace.c:3902

Memory state around the buggy address:
 ffff888048920000: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff888048920080: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
>ffff888048920100: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
                         ^
 ffff888048920180: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff888048920200: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
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