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KASAN: use-after-free Read in bch2_check_dirents

Status: upstream: reported C repro on 2024/11/15 11:11
Subsystems: bcachefs
[Documentation on labels]
Reported-by: syzbot+fea0322882c0cba65f11@syzkaller.appspotmail.com
Fix commit: bcachefs: Fix UAF in check_dirent()
Patched on: [ci-upstream-linux-next-kasan-gce-root ci-upstream-rust-kasan-gce], missing on: [ci-qemu-gce-upstream-auto ci-qemu-native-arm64-kvm ci-qemu-upstream ci-qemu-upstream-386 ci-qemu2-arm32 ci-qemu2-arm64 ci-qemu2-arm64-compat ci-qemu2-arm64-mte ci-qemu2-riscv64 ci-snapshot-upstream-root ci-upstream-bpf-kasan-gce ci-upstream-bpf-next-kasan-gce ci-upstream-gce-arm64 ci-upstream-gce-leak ci-upstream-kasan-badwrites-root ci-upstream-kasan-gce ci-upstream-kasan-gce-386 ci-upstream-kasan-gce-root ci-upstream-kasan-gce-selinux-root ci-upstream-kasan-gce-smack-root ci-upstream-kmsan-gce-386-root ci-upstream-kmsan-gce-root ci-upstream-net-kasan-gce ci-upstream-net-this-kasan-gce ci2-upstream-fs ci2-upstream-kcsan-gce ci2-upstream-usb]
First crash: 264d, last: 4h45m
Cause bisection: introduced by (bisect log) :
commit d97de0d017cde0d442c3d144b4f969f43064cc0f
Author: Kent Overstreet <kent.overstreet@linux.dev>
Date: Tue Aug 13 01:31:25 2024 +0000

  bcachefs: Make bkey_fsck_err() a wrapper around fsck_err()

Crash: kernel BUG in vfs_get_tree (log)
Repro: C syz .config
  
▶ ▼ Discussions (1)
Title Replies (including bot) Last reply
[syzbot] [bcachefs?] KASAN: use-after-free Read in bch2_check_dirents 0 (2) 2024/12/05 20:34
▶ ▼ Last patch testing requests (1)
Created Duration User Patch Repo Result
2024/11/29 04:50 18m retest repro upstream report log
▶ ▼ Cause bisection attempts (2)
Created Duration User Patch Repo Result
2024/12/05 12:29 8h04m bisect upstream OK (1) job log log
2024/11/15 04:47 11h03m bisect upstream OK (1) job log log
marked invalid by nogikh@google.com

Sample crash report:
bcachefs (loop0): check_inodes... done
bcachefs (loop0): check_extents... done
bcachefs (loop0): check_dirents...
dirent points to missing inode:
u64s 8 type dirent 4096:6728544935518790663:U32_MAX len 0 ver 0: lost+found -> 4097 type dir, fixing
==================================================================
BUG: KASAN: use-after-free in check_dirent fs/bcachefs/fsck.c:2443 [inline]
BUG: KASAN: use-after-free in bch2_check_dirents+0x2b68/0x3e90 fs/bcachefs/fsck.c:2468
Read of size 1 at addr ffff88805d564048 by task syz-executor265/6269

CPU: 1 UID: 0 PID: 6269 Comm: syz-executor265 Not tainted 6.14.0-rc3-syzkaller-00166-g334426094588 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 12/27/2024
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:408 [inline]
 print_report+0x16e/0x5b0 mm/kasan/report.c:521
 kasan_report+0x143/0x180 mm/kasan/report.c:634
 check_dirent fs/bcachefs/fsck.c:2443 [inline]
 bch2_check_dirents+0x2b68/0x3e90 fs/bcachefs/fsck.c:2468
 bch2_run_recovery_pass+0xf0/0x1e0 fs/bcachefs/recovery_passes.c:226
 bch2_run_recovery_passes+0x2ad/0xa90 fs/bcachefs/recovery_passes.c:291
 bch2_fs_recovery+0x2c48/0x3de0 fs/bcachefs/recovery.c:973
 bch2_fs_start+0x37c/0x610 fs/bcachefs/super.c:1041
 bch2_fs_get_tree+0xdb7/0x17a0 fs/bcachefs/fs.c:2203
 vfs_get_tree+0x90/0x2b0 fs/super.c:1814
 do_new_mount+0x2be/0xb40 fs/namespace.c:3560
 do_mount fs/namespace.c:3900 [inline]
 __do_sys_mount fs/namespace.c:4111 [inline]
 __se_sys_mount+0x2d6/0x3c0 fs/namespace.c:4088
 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: 0033:0x7eff7d61461a
Code: d8 64 89 02 48 c7 c0 ff ff ff ff eb a6 e8 5e 04 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 b8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007ffd68e9c008 EFLAGS: 00000282 ORIG_RAX: 00000000000000a5
RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00007eff7d61461a
RDX: 0000400000000000 RSI: 0000400000000040 RDI: 00007ffd68e9c050
RBP: 0000000000000004 R08: 00007ffd68e9c090 R09: 0000000000005956
R10: 0000000001000001 R11: 0000000000000282 R12: 0000000001000000
R13: 00007ffd68e9c090 R14: 0000400000000000 R15: 0000000000000003
 </TASK>

The buggy address belongs to the physical page:
page: refcount:0 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x5d564
flags: 0xfff00000000000(node=0|zone=1|lastcpupid=0x7ff)
raw: 00fff00000000000 0000000000000000 dead000000000122 0000000000000000
raw: 0000000000000000 0000000000000000 00000000ffffffff 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 6269, tgid 6269 (syz-executor265), ts 106334437847, free_ts 106682597280
 set_page_owner include/linux/page_owner.h:32 [inline]
 post_alloc_hook+0x1f4/0x240 mm/page_alloc.c:1551
 prep_new_page mm/page_alloc.c:1559 [inline]
 get_page_from_freelist+0x3651/0x37a0 mm/page_alloc.c:3477
 __alloc_frozen_pages_noprof+0x292/0x710 mm/page_alloc.c:4739
 __alloc_pages_noprof+0xa/0x30 mm/page_alloc.c:4773
 __alloc_pages_node_noprof include/linux/gfp.h:265 [inline]
 alloc_pages_node_noprof include/linux/gfp.h:292 [inline]
 ___kmalloc_large_node+0x8b/0x1d0 mm/slub.c:4239
 __kmalloc_large_node_noprof+0x1a/0x80 mm/slub.c:4266
 __do_kmalloc_node mm/slub.c:4282 [inline]
 __kmalloc_node_noprof+0x33a/0x4d0 mm/slub.c:4300
 __kvmalloc_node_noprof+0x72/0x190 mm/util.c:662
 btree_bounce_alloc fs/bcachefs/btree_io.c:123 [inline]
 btree_node_sort+0x620/0x1830 fs/bcachefs/btree_io.c:322
 bch2_btree_post_write_cleanup+0x11a/0xa70 fs/bcachefs/btree_io.c:2293
 bch2_btree_node_prep_for_write+0x345/0x660 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:862 [inline]
 __bch2_trans_commit+0x258c/0x9790 fs/bcachefs/btree_trans_commit.c:1070
 __bch2_str_hash_check_key+0x1ea4/0x3ac0
 bch2_str_hash_check_key fs/bcachefs/str_hash.h:415 [inline]
 check_dirent fs/bcachefs/fsck.c:2373 [inline]
 bch2_check_dirents+0x2eb0/0x3e90 fs/bcachefs/fsck.c:2468
 bch2_run_recovery_pass+0xf0/0x1e0 fs/bcachefs/recovery_passes.c:226
page last free pid 6269 tgid 6269 stack trace:
 reset_page_owner include/linux/page_owner.h:25 [inline]
 free_pages_prepare mm/page_alloc.c:1127 [inline]
 __free_pages_ok+0xbbc/0xe40 mm/page_alloc.c:1271
 __folio_put+0x2b3/0x360 mm/swap.c:112
 folio_put include/linux/mm.h:1489 [inline]
 free_large_kmalloc+0xfe/0x180 mm/slub.c:4728
 kfree+0x212/0x430 mm/slub.c:4751
 btree_bounce_free fs/bcachefs/btree_io.c:111 [inline]
 btree_node_sort+0x1100/0x1830 fs/bcachefs/btree_io.c:379
 bch2_btree_post_write_cleanup+0x11a/0xa70 fs/bcachefs/btree_io.c:2293
 bch2_btree_node_prep_for_write+0x345/0x660 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:862 [inline]
 __bch2_trans_commit+0x258c/0x9790 fs/bcachefs/btree_trans_commit.c:1070
 bch2_trans_commit fs/bcachefs/btree_update.h:183 [inline]
 check_dirent fs/bcachefs/fsck.c:2438 [inline]
 bch2_check_dirents+0x28be/0x3e90 fs/bcachefs/fsck.c:2468
 bch2_run_recovery_pass+0xf0/0x1e0 fs/bcachefs/recovery_passes.c:226
 bch2_run_recovery_passes+0x2ad/0xa90 fs/bcachefs/recovery_passes.c:291
 bch2_fs_recovery+0x2c48/0x3de0 fs/bcachefs/recovery.c:973
 bch2_fs_start+0x37c/0x610 fs/bcachefs/super.c:1041
 bch2_fs_get_tree+0xdb7/0x17a0 fs/bcachefs/fs.c:2203
 vfs_get_tree+0x90/0x2b0 fs/super.c:1814

Memory state around the buggy address:
 ffff88805d563f00: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff88805d563f80: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
>ffff88805d564000: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
                                              ^
 ffff88805d564080: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff88805d564100: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
==================================================================

Crashes (611):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2025/02/21 13:25 upstream 334426094588 0808a665 .config strace log report syz / log C [disk image] [vmlinux] [kernel image] [mounted in repro] ci2-upstream-fs KASAN: use-after-free Read in bch2_check_dirents
2024/11/15 04:43 upstream cfaaa7d010d1 a8c99394 .config console log report syz / log C [disk image] [vmlinux] [kernel image] [mounted in repro] ci2-upstream-fs KASAN: use-after-free Read in bch2_check_dirents
2025/02/15 03:49 linux-next 0ae0fa3bf0b4 40a34ec9 .config console log report syz / log C [disk image] [vmlinux] [kernel image] [mounted in repro] ci-upstream-linux-next-kasan-gce-root KASAN: use-after-free Read in bch2_check_dirents
2025/07/23 02:34 upstream 89be9a83ccf1 8e9d1dc1 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-fs KASAN: use-after-free Read in bch2_check_dirents
2025/07/13 23:41 upstream 5d5d62298b8b 3cda49cf .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-root KASAN: use-after-free Read in bch2_check_dirents
2025/08/06 20:25 upstream 479058002c32 4bd24a3e .config console log report [disk image (non-bootable)] [vmlinux] [kernel image] ci-snapshot-upstream-root KASAN: use-after-free Read in bch2_check_dirents
2025/08/06 05:29 upstream 6bcdbd62bd56 ffe1dd46 .config console log report [disk image (non-bootable)] [vmlinux] [kernel image] ci-snapshot-upstream-root KASAN: use-after-free Read in bch2_check_dirents
2025/08/05 20:10 upstream 7e161a991ea7 37880f40 .config console log report [disk image (non-bootable)] [vmlinux] [kernel image] ci-snapshot-upstream-root KASAN: use-after-free Read in bch2_check_dirents
2025/08/05 05:22 upstream 35a813e010b9 f5bcc8dc .config console log report [disk image (non-bootable)] [vmlinux] [kernel image] ci-snapshot-upstream-root KASAN: use-after-free Read in bch2_check_dirents
2025/08/04 16:38 upstream d2eedaa3909b abdcb213 .config console log report [disk image (non-bootable)] [vmlinux] [kernel image] ci-snapshot-upstream-root KASAN: use-after-free Read in bch2_check_dirents
2025/08/04 15:19 upstream d2eedaa3909b abdcb213 .config console log report [disk image (non-bootable)] [vmlinux] [kernel image] ci-snapshot-upstream-root KASAN: use-after-free Read in bch2_check_dirents
2025/08/03 04:44 upstream eacf91b0c78a 7368264b .config console log report [disk image (non-bootable)] [vmlinux] [kernel image] ci-snapshot-upstream-root KASAN: use-after-free Read in bch2_check_dirents
2025/08/03 01:50 upstream eacf91b0c78a 7368264b .config console log report [disk image (non-bootable)] [vmlinux] [kernel image] ci-snapshot-upstream-root KASAN: use-after-free Read in bch2_check_dirents
2025/08/03 00:11 upstream eacf91b0c78a 7368264b .config console log report [disk image (non-bootable)] [vmlinux] [kernel image] ci-snapshot-upstream-root KASAN: use-after-free Read in bch2_check_dirents
2025/08/02 20:55 upstream eacf91b0c78a 7368264b .config console log report [disk image (non-bootable)] [vmlinux] [kernel image] ci-snapshot-upstream-root KASAN: use-after-free Read in bch2_check_dirents
2025/08/02 15:17 upstream a6923c06a3b2 7368264b .config console log report [disk image (non-bootable)] [vmlinux] [kernel image] ci-snapshot-upstream-root KASAN: use-after-free Read in bch2_check_dirents
2025/08/02 03:27 upstream a6923c06a3b2 7368264b .config console log report [disk image (non-bootable)] [vmlinux] [kernel image] ci-snapshot-upstream-root KASAN: use-after-free Read in bch2_check_dirents
2025/08/01 07:36 upstream d6084bb815c4 0c075d67 .config console log report [disk image (non-bootable)] [vmlinux] [kernel image] ci-snapshot-upstream-root KASAN: use-after-free Read in bch2_check_dirents
2025/08/01 00:06 upstream d6084bb815c4 3526e777 .config console log report [disk image (non-bootable)] [vmlinux] [kernel image] ci-snapshot-upstream-root KASAN: use-after-free Read in bch2_check_dirents
2025/07/31 16:59 upstream 260f6f4fda93 3526e777 .config console log report [disk image (non-bootable)] [vmlinux] [kernel image] ci-snapshot-upstream-root KASAN: use-after-free Read in bch2_check_dirents
2025/07/31 15:11 upstream 260f6f4fda93 3526e777 .config console log report [disk image (non-bootable)] [vmlinux] [kernel image] ci-snapshot-upstream-root KASAN: use-after-free Read in bch2_check_dirents
2025/07/31 07:17 upstream 260f6f4fda93 f8f2b4da .config console log report [disk image (non-bootable)] [vmlinux] [kernel image] ci-snapshot-upstream-root KASAN: use-after-free Read in bch2_check_dirents
2025/07/30 14:32 upstream 14bed9bc81ba f8f2b4da .config console log report [disk image (non-bootable)] [vmlinux] [kernel image] ci-snapshot-upstream-root KASAN: use-after-free Read in bch2_check_dirents
2025/07/30 07:17 upstream 14bed9bc81ba f8f2b4da .config console log report [disk image (non-bootable)] [vmlinux] [kernel image] ci-snapshot-upstream-root KASAN: use-after-free Read in bch2_check_dirents
2025/07/30 05:11 upstream 14bed9bc81ba f8f2b4da .config console log report [disk image (non-bootable)] [vmlinux] [kernel image] ci-snapshot-upstream-root KASAN: use-after-free Read in bch2_check_dirents
2025/07/30 03:56 upstream 14bed9bc81ba f8f2b4da .config console log report [disk image (non-bootable)] [vmlinux] [kernel image] ci-snapshot-upstream-root KASAN: use-after-free Read in bch2_check_dirents
2025/07/29 18:10 upstream 86aa72182095 ba28e0a8 .config console log report [disk image (non-bootable)] [vmlinux] [kernel image] ci-snapshot-upstream-root KASAN: use-after-free Read in bch2_check_dirents
2025/07/28 01:29 upstream b711733e89a3 fb8f743d .config console log report [disk image (non-bootable)] [vmlinux] [kernel image] ci-snapshot-upstream-root KASAN: use-after-free Read in bch2_check_dirents
2025/07/27 11:41 upstream ec2df4364666 fb8f743d .config console log report [disk image (non-bootable)] [vmlinux] [kernel image] ci-snapshot-upstream-root KASAN: use-after-free Read in bch2_check_dirents
2025/07/27 08:18 upstream ec2df4364666 fb8f743d .config console log report [disk image (non-bootable)] [vmlinux] [kernel image] ci-snapshot-upstream-root KASAN: use-after-free Read in bch2_check_dirents
2025/07/26 22:05 upstream 302f88ff3584 fb8f743d .config console log report [disk image (non-bootable)] [vmlinux] [kernel image] ci-snapshot-upstream-root KASAN: use-after-free Read in bch2_check_dirents
2025/07/26 15:34 upstream 5f33ebd2018c fb8f743d .config console log report [disk image (non-bootable)] [vmlinux] [kernel image] ci-snapshot-upstream-root KASAN: use-after-free Read in bch2_check_dirents
2025/07/26 14:30 upstream 5f33ebd2018c fb8f743d .config console log report [disk image (non-bootable)] [vmlinux] [kernel image] ci-snapshot-upstream-root KASAN: use-after-free Read in bch2_check_dirents
2025/07/25 21:33 upstream 2942242dde89 fb8f743d .config console log report [disk image (non-bootable)] [vmlinux] [kernel image] ci-snapshot-upstream-root KASAN: use-after-free Read in bch2_check_dirents
2025/07/24 17:44 upstream 25fae0b93d1d 65d60d73 .config console log report [disk image (non-bootable)] [vmlinux] [kernel image] ci-snapshot-upstream-root KASAN: use-after-free Read in bch2_check_dirents
2025/07/24 11:44 upstream f9af7b5d9349 0c1d6ded .config console log report [disk image (non-bootable)] [vmlinux] [kernel image] ci-snapshot-upstream-root KASAN: use-after-free Read in bch2_check_dirents
2025/07/24 06:50 upstream f9af7b5d9349 0c1d6ded .config console log report [disk image (non-bootable)] [vmlinux] [kernel image] ci-snapshot-upstream-root KASAN: use-after-free Read in bch2_check_dirents
2025/07/22 10:57 upstream 89be9a83ccf1 1555463b .config console log report [disk image (non-bootable)] [vmlinux] [kernel image] ci-snapshot-upstream-root KASAN: use-after-free Read in bch2_check_dirents
2025/07/21 21:24 upstream 89be9a83ccf1 56d87229 .config console log report [disk image (non-bootable)] [vmlinux] [kernel image] ci-snapshot-upstream-root KASAN: use-after-free Read in bch2_check_dirents
2025/07/20 04:58 upstream bf61759db409 7117feec .config console log report [disk image (non-bootable)] [vmlinux] [kernel image] ci-snapshot-upstream-root KASAN: use-after-free Read in bch2_check_dirents
2025/07/18 10:03 upstream 6832a9317eee 88248e14 .config console log report [disk image (non-bootable)] [vmlinux] [kernel image] ci-snapshot-upstream-root KASAN: use-after-free Read in bch2_check_dirents
2025/07/16 22:07 upstream 155a3c003e55 44f8051e .config console log report [disk image (non-bootable)] [vmlinux] [kernel image] ci-snapshot-upstream-root KASAN: use-after-free Read in bch2_check_dirents
2025/07/16 15:48 upstream 155a3c003e55 124ec9cc .config console log report [disk image (non-bootable)] [vmlinux] [kernel image] ci-snapshot-upstream-root KASAN: use-after-free Read in bch2_check_dirents
2025/07/16 06:36 upstream 155a3c003e55 03fcfc4b .config console log report [disk image (non-bootable)] [vmlinux] [kernel image] ci-snapshot-upstream-root KASAN: use-after-free Read in bch2_check_dirents
2025/07/15 23:30 upstream 155a3c003e55 03fcfc4b .config console log report [disk image (non-bootable)] [vmlinux] [kernel image] ci-snapshot-upstream-root KASAN: use-after-free Read in bch2_check_dirents
2025/07/15 14:17 upstream 155a3c003e55 03fcfc4b .config console log report [disk image (non-bootable)] [vmlinux] [kernel image] ci-snapshot-upstream-root KASAN: use-after-free Read in bch2_check_dirents
2025/07/15 12:26 upstream 155a3c003e55 03fcfc4b .config console log report [disk image (non-bootable)] [vmlinux] [kernel image] ci-snapshot-upstream-root KASAN: use-after-free Read in bch2_check_dirents
2025/07/15 08:50 upstream 155a3c003e55 03fcfc4b .config console log report [disk image (non-bootable)] [vmlinux] [kernel image] ci-snapshot-upstream-root KASAN: use-after-free Read in bch2_check_dirents
2025/06/29 19:31 linux-next 2aeda9592360 fc9d8ee5 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-linux-next-kasan-gce-root KASAN: use-after-free Read in bch2_check_dirents
2025/08/02 13:29 git://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux.git for-kernelci 82af5ea7c611 7368264b .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-gce-arm64 KASAN: use-after-free Read in bch2_check_dirents
2025/08/01 07:49 git://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux.git for-kernelci 82af5ea7c611 0c075d67 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-gce-arm64 KASAN: use-after-free Read in bch2_check_dirents
2025/07/29 04:57 git://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux.git for-kernelci 82af5ea7c611 c4a95487 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-gce-arm64 KASAN: use-after-free Read in bch2_check_dirents
2025/06/21 17:08 upstream 3f75bfff44be d6cdfb8a .config console log report [disk image (non-bootable)] [vmlinux] [kernel image] ci-snapshot-upstream-root KASAN: slab-use-after-free Read in bch2_check_dirents
* Struck through repros no longer work on HEAD.