KASAN: slab-use-after-free Read in bchfs_read

Status: fixed on 2025/06/10 16:19
Subsystems: fs
[Documentation on labels]
Reported-by: syzbot+2deb10b8dc9aae6fab67@syzkaller.appspotmail.com
Fix commit: 34b47e3d73a2 bcachefs: Fix UAF in bchfs_read()
First crash: 491d, last: 480d
Cause bisection: introduced by (bisect log) :
commit 3ba0240a8789f8c059990b81c6f34c29769a5a49
Author: Kent Overstreet <kent.overstreet@linux.dev>
Date: Mon Mar 24 15:51:01 2025 +0000

  bcachefs: Fix silent short reads in data read retry path

Crash: KASAN: slab-use-after-free Read in bchfs_read (log)
Repro: C syz .config
  
▶ ▼ Discussions (1)
Title Replies (including bot) Last reply
[syzbot] [bcachefs?] KASAN: slab-use-after-free Read in bchfs_read 1 (3) 2025/04/05 20:37
▶ ▼ Last patch testing requests (1)
Created Duration User Patch Repo Result
2025/04/05 16:45 1h11m kent.overstreet@linux.dev patch upstream report log

Sample crash report:
==================================================================
BUG: KASAN: slab-use-after-free in bchfs_read+0x2b48/0x3350 fs/bcachefs/fs-io-buffered.c:228
Read of size 4 at addr ffff8880756ac148 by task syz-executor406/5854

CPU: 0 UID: 0 PID: 5854 Comm: syz-executor406 Not tainted 6.14.0-syzkaller-12456-gacc4d5ff0b61 #0 PREEMPT(full) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2025
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
 bchfs_read+0x2b48/0x3350 fs/bcachefs/fs-io-buffered.c:228
 bch2_readahead+0xe7a/0x12d0 fs/bcachefs/fs-io-buffered.c:301
 read_pages+0x193/0x590 mm/readahead.c:160
 page_cache_ra_order+0xa37/0xca0 mm/readahead.c:515
 filemap_get_pages+0x59f/0x1fc0 mm/filemap.c:2590
 filemap_read+0x466/0x1260 mm/filemap.c:2701
 bch2_read_iter+0x1179/0x14b0 fs/bcachefs/fs-io-direct.c:221
 new_sync_read fs/read_write.c:489 [inline]
 vfs_read+0x9a0/0xb90 fs/read_write.c:570
 ksys_read+0x19d/0x2d0 fs/read_write.c:713
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xf3/0x230 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7fc1adbabc59
Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 01 1b 00 00 90 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 b8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007ffd419910a8 EFLAGS: 00000246 ORIG_RAX: 0000000000000000
RAX: ffffffffffffffda RBX: 00007ffd419910d0 RCX: 00007fc1adbabc59
RDX: 0000000000002020 RSI: 0000200000000800 RDI: 0000000000000004
RBP: 0000000000000001 R08: 00007ffd41990e47 R09: 00007ffd419910f0
R10: 0000000000000001 R11: 0000000000000246 R12: 00007ffd419910cc
R13: 0000000000000002 R14: 431bde82d7b634db R15: 00007ffd41991110
 </TASK>

Allocated by task 5854:
 kasan_save_stack mm/kasan/common.c:47 [inline]
 kasan_save_track+0x3f/0x80 mm/kasan/common.c:68
 unpoison_slab_object mm/kasan/common.c:319 [inline]
 __kasan_mempool_unpoison_object+0x9e/0x170 mm/kasan/common.c:547
 kasan_unpoison_element mm/mempool.c:-1 [inline]
 remove_element+0x129/0x1a0 mm/mempool.c:150
 mempool_alloc_noprof+0x552/0x5a0 mm/mempool.c:408
 bio_alloc_bioset+0x26f/0x1130 block/bio.c:554
 bch2_readahead+0xbaf/0x12d0 fs/bcachefs/fs-io-buffered.c:290
 read_pages+0x193/0x590 mm/readahead.c:160
 page_cache_ra_order+0xa37/0xca0 mm/readahead.c:515
 filemap_get_pages+0x59f/0x1fc0 mm/filemap.c:2590
 filemap_read+0x466/0x1260 mm/filemap.c:2701
 bch2_read_iter+0x1179/0x14b0 fs/bcachefs/fs-io-direct.c:221
 new_sync_read fs/read_write.c:489 [inline]
 vfs_read+0x9a0/0xb90 fs/read_write.c:570
 ksys_read+0x19d/0x2d0 fs/read_write.c:713
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xf3/0x230 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

Freed by task 5854:
 kasan_save_stack mm/kasan/common.c:47 [inline]
 kasan_save_track+0x3f/0x80 mm/kasan/common.c:68
 kasan_save_free_info+0x40/0x50 mm/kasan/generic.c:576
 poison_slab_object mm/kasan/common.c:247 [inline]
 __kasan_mempool_poison_object+0xaa/0x120 mm/kasan/common.c:522
 kasan_mempool_poison_object include/linux/kasan.h:360 [inline]
 kasan_poison_element mm/mempool.c:118 [inline]
 add_element mm/mempool.c:141 [inline]
 mempool_free+0x1c8/0x390 mm/mempool.c:541
 bch2_readpages_end_io+0x17c/0x1d0 fs/bcachefs/fs-io-buffered.c:36
 bch2_rbio_done fs/bcachefs/io_read.c:430 [inline]
 __bch2_read_extent+0x1348/0x4400 fs/bcachefs/io_read.c:1257
 bch2_read_extent fs/bcachefs/io_read.h:140 [inline]
 bchfs_read+0x251a/0x3350 fs/bcachefs/fs-io-buffered.c:226
 bch2_readahead+0xe7a/0x12d0 fs/bcachefs/fs-io-buffered.c:301
 read_pages+0x193/0x590 mm/readahead.c:160
 page_cache_ra_order+0xa37/0xca0 mm/readahead.c:515
 filemap_get_pages+0x59f/0x1fc0 mm/filemap.c:2590
 filemap_read+0x466/0x1260 mm/filemap.c:2701
 bch2_read_iter+0x1179/0x14b0 fs/bcachefs/fs-io-direct.c:221
 new_sync_read fs/read_write.c:489 [inline]
 vfs_read+0x9a0/0xb90 fs/read_write.c:570
 ksys_read+0x19d/0x2d0 fs/read_write.c:713
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xf3/0x230 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

The buggy address belongs to the object at ffff8880756ac000
 which belongs to the cache bio-488 of size 488
The buggy address is located 328 bytes inside of
 freed 488-byte region [ffff8880756ac000, ffff8880756ac1e8)

The buggy address belongs to the physical page:
page: refcount:0 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x756ac
head: order:1 mapcount:0 entire_mapcount:0 nr_pages_mapped:0 pincount:0
flags: 0xfff00000000040(head|node=0|zone=1|lastcpupid=0x7ff)
page_type: f5(slab)
raw: 00fff00000000040 ffff888033497a00 dead000000000122 0000000000000000
raw: 0000000000000000 00000000800c000c 00000000f5000000 0000000000000000
head: 00fff00000000040 ffff888033497a00 dead000000000122 0000000000000000
head: 0000000000000000 00000000800c000c 00000000f5000000 0000000000000000
head: 00fff00000000001 ffffea0001d5ab01 00000000ffffffff 00000000ffffffff
head: ffffffffffffffff 0000000000000000 00000000ffffffff 0000000000000002
page dumped because: kasan: bad access detected
page_owner tracks the page as allocated
page last allocated via order 1, migratetype Unmovable, gfp_mask 0xd20c0(__GFP_IO|__GFP_FS|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC), pid 5854, tgid 5854 (syz-executor406), ts 92613750343, free_ts 91077243774
 set_page_owner include/linux/page_owner.h:32 [inline]
 post_alloc_hook+0x1f4/0x240 mm/page_alloc.c:1717
 prep_new_page mm/page_alloc.c:1725 [inline]
 get_page_from_freelist+0x351d/0x36b0 mm/page_alloc.c:3652
 __alloc_frozen_pages_noprof+0x211/0x5b0 mm/page_alloc.c:4934
 alloc_pages_mpol+0x339/0x690 mm/mempolicy.c:2301
 alloc_slab_page mm/slub.c:2459 [inline]
 allocate_slab+0x8f/0x3a0 mm/slub.c:2623
 new_slab mm/slub.c:2676 [inline]
 ___slab_alloc+0xc3b/0x1500 mm/slub.c:3862
 __slab_alloc+0x58/0xa0 mm/slub.c:3952
 __slab_alloc_node mm/slub.c:4027 [inline]
 slab_alloc_node mm/slub.c:4188 [inline]
 kmem_cache_alloc_noprof+0x270/0x390 mm/slub.c:4207
 mempool_init_node+0x1ee/0x4e0 mm/mempool.c:217
 mempool_init_noprof+0x3a/0x50 mm/mempool.c:246
 bioset_init+0x2ea/0x820 block/bio.c:1709
 bch2_fs_io_read_init+0x29/0xc0 fs/bcachefs/io_read.c:1377
 bch2_fs_alloc fs/bcachefs/super.c:944 [inline]
 bch2_fs_open+0x2f2f/0x32a0 fs/bcachefs/super.c:2182
 bch2_fs_get_tree+0x77b/0x18f0 fs/bcachefs/fs.c:2172
 vfs_get_tree+0x90/0x2b0 fs/super.c:1759
 do_new_mount+0x2cf/0xb70 fs/namespace.c:3878
page last free pid 5830 tgid 5830 stack trace:
 reset_page_owner include/linux/page_owner.h:25 [inline]
 free_pages_prepare mm/page_alloc.c:1262 [inline]
 __free_pages_ok+0xb17/0xd90 mm/page_alloc.c:1437
 __folio_put+0x2b5/0x360 mm/swap.c:112
 folio_put include/linux/mm.h:1563 [inline]
 free_large_kmalloc+0x143/0x1e0 mm/slub.c:4771
 kfree+0x216/0x430 mm/slub.c:4839
 bch2_dev_journal_exit+0x2ba/0x4a0 fs/bcachefs/journal.c:1478
 bch2_dev_free+0x14d/0x230 fs/bcachefs/super.c:1220
 bch2_fs_free+0x27b/0x3c0 fs/bcachefs/super.c:679
 deactivate_locked_super+0xc4/0x130 fs/super.c:473
 cleanup_mnt+0x422/0x4c0 fs/namespace.c:1435
 task_work_run+0x251/0x310 kernel/task_work.c:227
 ptrace_notify+0x2dc/0x390 kernel/signal.c:2522
 ptrace_report_syscall include/linux/ptrace.h:415 [inline]
 ptrace_report_syscall_exit include/linux/ptrace.h:477 [inline]
 syscall_exit_work+0xc7/0x1d0 kernel/entry/common.c:173
 syscall_exit_to_user_mode_prepare kernel/entry/common.c:200 [inline]
 __syscall_exit_to_user_mode_work kernel/entry/common.c:205 [inline]
 syscall_exit_to_user_mode+0x24a/0x340 kernel/entry/common.c:218
 do_syscall_64+0x100/0x230 arch/x86/entry/syscall_64.c:100
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

Memory state around the buggy address:
 ffff8880756ac000: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff8880756ac080: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff8880756ac100: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                                              ^
 ffff8880756ac180: fb fb fb fb fb fb fb fb fb fb fb fb fb fc fc fc
 ffff8880756ac200: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
==================================================================

Crashes (34):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2025/04/02 17:39 upstream acc4d5ff0b61 c799dfdd .config strace log report syz / log C [disk image] [vmlinux] [kernel image] [mounted in repro] ci2-upstream-fs KASAN: slab-use-after-free Read in bchfs_read
2025/04/10 09:05 upstream 3b07108ada81 988b336c .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-fs KASAN: slab-use-after-free Read in bchfs_read
2025/04/09 23:47 upstream a24588245776 988b336c .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-fs KASAN: slab-use-after-free Read in bchfs_read
2025/04/09 19:21 upstream a24588245776 47d015b1 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-fs KASAN: slab-use-after-free Read in bchfs_read
2025/04/09 17:09 upstream a24588245776 47d015b1 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-fs KASAN: slab-use-after-free Read in bchfs_read
2025/04/08 18:22 upstream 0af2f6be1b42 a775275d .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-fs KASAN: slab-use-after-free Read in bchfs_read
2025/04/02 14:39 upstream acc4d5ff0b61 c799dfdd .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-fs KASAN: slab-use-after-free Read in bchfs_read
2025/04/10 18:43 upstream 2eb959eeecc6 1ef3ab4d .config console log report [disk image (non-bootable)] [vmlinux] [kernel image] ci-snapshot-upstream-root KASAN: slab-use-after-free Read in bchfs_read
2025/04/10 17:55 upstream 2eb959eeecc6 1ef3ab4d .config console log report [disk image (non-bootable)] [vmlinux] [kernel image] ci-snapshot-upstream-root KASAN: slab-use-after-free Read in bchfs_read
2025/04/10 12:07 upstream 3b07108ada81 1ef3ab4d .config console log report [disk image (non-bootable)] [vmlinux] [kernel image] ci-snapshot-upstream-root KASAN: slab-use-after-free Read in bchfs_read
2025/04/10 09:47 upstream 3b07108ada81 988b336c .config console log report [disk image (non-bootable)] [vmlinux] [kernel image] ci-snapshot-upstream-root KASAN: slab-use-after-free Read in bchfs_read
2025/04/09 08:55 upstream bec7dcbc242c b133e63a .config console log report [disk image (non-bootable)] [vmlinux] [kernel image] ci-snapshot-upstream-root KASAN: slab-use-after-free Read in bchfs_read
2025/04/08 18:41 upstream 0af2f6be1b42 a775275d .config console log report [disk image (non-bootable)] [vmlinux] [kernel image] ci-snapshot-upstream-root KASAN: slab-use-after-free Read in bchfs_read
2025/04/08 11:25 upstream 0af2f6be1b42 a775275d .config console log report [disk image (non-bootable)] [vmlinux] [kernel image] ci-snapshot-upstream-root KASAN: slab-use-after-free Read in bchfs_read
2025/04/07 15:46 upstream 0af2f6be1b42 2f0c9720 .config console log report [disk image (non-bootable)] [vmlinux] [kernel image] ci-snapshot-upstream-root KASAN: slab-use-after-free Read in bchfs_read
2025/04/07 06:27 upstream 0af2f6be1b42 1c65791e .config console log report [disk image (non-bootable)] [vmlinux] [kernel image] ci-snapshot-upstream-root KASAN: slab-use-after-free Read in bchfs_read
2025/04/07 04:48 upstream 0af2f6be1b42 1c65791e .config console log report [disk image (non-bootable)] [vmlinux] [kernel image] ci-snapshot-upstream-root KASAN: slab-use-after-free Read in bchfs_read
2025/04/07 04:30 upstream 0af2f6be1b42 1c65791e .config console log report [disk image (non-bootable)] [vmlinux] [kernel image] ci-snapshot-upstream-root KASAN: slab-use-after-free Read in bchfs_read
2025/04/06 20:35 upstream f4d2ef48250a 1c65791e .config console log report [disk image (non-bootable)] [vmlinux] [kernel image] ci-snapshot-upstream-root KASAN: slab-use-after-free Read in bchfs_read
2025/04/06 16:51 upstream f4d2ef48250a 1c65791e .config console log report [disk image (non-bootable)] [vmlinux] [kernel image] ci-snapshot-upstream-root KASAN: slab-use-after-free Read in bchfs_read
2025/04/06 02:03 upstream 56f944529ec2 1c65791e .config console log report [disk image (non-bootable)] [vmlinux] [kernel image] ci-snapshot-upstream-root KASAN: slab-use-after-free Read in bchfs_read
2025/04/05 18:41 upstream a8662bcd2ff1 1c65791e .config console log report [disk image (non-bootable)] [vmlinux] [kernel image] ci-snapshot-upstream-root KASAN: slab-use-after-free Read in bchfs_read
2025/04/04 22:03 upstream e48e99b6edf4 c53ea9c9 .config console log report [disk image (non-bootable)] [vmlinux] [kernel image] ci-snapshot-upstream-root KASAN: slab-use-after-free Read in bchfs_read
2025/04/04 01:24 upstream a2cc6ff5ec8f d7ae3a11 .config console log report [disk image (non-bootable)] [vmlinux] [kernel image] ci-snapshot-upstream-root KASAN: slab-use-after-free Read in bchfs_read
2025/04/03 23:30 upstream a2cc6ff5ec8f d7ae3a11 .config console log report [disk image (non-bootable)] [vmlinux] [kernel image] ci-snapshot-upstream-root KASAN: slab-use-after-free Read in bchfs_read
2025/04/03 17:47 upstream a2cc6ff5ec8f d7ae3a11 .config console log report [disk image (non-bootable)] [vmlinux] [kernel image] ci-snapshot-upstream-root KASAN: slab-use-after-free Read in bchfs_read
2025/04/03 06:22 upstream a1b5bd45d4ee 996a9618 .config console log report [disk image (non-bootable)] [vmlinux] [kernel image] ci-snapshot-upstream-root KASAN: slab-use-after-free Read in bchfs_read
2025/04/02 23:39 upstream acc4d5ff0b61 b0cc4801 .config console log report [disk image (non-bootable)] [vmlinux] [kernel image] ci-snapshot-upstream-root KASAN: slab-use-after-free Read in bchfs_read
2025/04/02 11:29 upstream 91e5bfe317d8 c799dfdd .config console log report [disk image (non-bootable)] [vmlinux] [kernel image] ci-snapshot-upstream-root KASAN: slab-use-after-free Read in bchfs_read
2025/04/01 10:29 upstream 08733088b566 36d76a97 .config console log report [disk image (non-bootable)] [vmlinux] [kernel image] ci-snapshot-upstream-root KASAN: slab-use-after-free Read in bchfs_read
2025/04/03 00:44 linux-next fefb886b1344 996a9618 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-linux-next-kasan-gce-root KASAN: slab-use-after-free Read in bchfs_read
2025/04/02 06:30 linux-next fefb886b1344 c799dfdd .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-linux-next-kasan-gce-root KASAN: slab-use-after-free Read in bchfs_read
2025/04/12 12:56 git://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux.git for-kernelci 2fe2b96c3818 0bd6db41 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-gce-arm64 KASAN: slab-use-after-free Read in bchfs_read
2025/04/09 00:36 git://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux.git for-kernelci 0af2f6be1b42 b133e63a .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-gce-arm64 KASAN: slab-use-after-free Read in bchfs_read
* Struck through repros no longer work on HEAD.