KASAN: use-after-free Read in leaf_paste_in_buffer

Status: upstream: reported C repro on 2025/07/09 14:00
Bug presence: origin:lts-only
[Documentation on labels]
Reported-by: syzbot+ef4ab278e3f74d7865eb@syzkaller.appspotmail.com
First crash: 383d, last: 178d
▶ ▼ Bug presence (2)
Date Name Commit Repro Result
2025/08/29 linux-6.6.y (ToT) cc1a1c5b404a C [report] KASAN: use-after-free Read in leaf_paste_in_buffer
2025/08/29 upstream (ToT) fb679c832b64 C Didn't crash
▶ ▼ Similar bugs (5)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
linux-5.15 KASAN: out-of-bounds Read in leaf_paste_in_buffer missing-backport origin:upstream 22 C done 277 13d 1135d 0/3 upstream: reported C repro on 2023/06/18 14:09
linux-4.14 KASAN: out-of-bounds Read in leaf_paste_in_buffer reiserfs 22 C 6 1240d 1332d 0/1 upstream: reported C repro on 2022/12/03 21:39
linux-4.19 KASAN: out-of-bounds Read in leaf_paste_in_buffer reiserfs 19 C 13 1265d 1339d 0/1 upstream: reported C repro on 2022/11/27 00:33
upstream KASAN: use-after-free Read in leaf_paste_in_buffer fs 22 C error done 310 909d 1334d 0/29 auto-obsoleted due to no activity on 2024/04/09 15:59
linux-6.1 KASAN: use-after-free Read in leaf_paste_in_buffer origin:upstream missing-backport 22 C done 272 21h58m 1137d 0/3 upstream: reported C repro on 2023/06/16 18:50
▶ ▼ Fix bisection attempts (1)
Created Duration User Patch Repo Result
2025/09/01 20:58 2h23m fix candidate upstream OK (0) job log

Sample crash report:
==================================================================
BUG: KASAN: use-after-free in leaf_paste_in_buffer+0x6a1/0xbd0 fs/reiserfs/lbalance.c:-1
Read of size 48 at addr ffff88806b707ff0 by task syz.0.30/6009

CPU: 0 PID: 6009 Comm: syz.0.30 Not tainted 6.6.101-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/12/2025
Call Trace:
 <TASK>
 dump_stack_lvl+0x16c/0x230 lib/dump_stack.c:106
 print_address_description mm/kasan/report.c:364 [inline]
 print_report+0xac/0x220 mm/kasan/report.c:468
 kasan_report+0x117/0x150 mm/kasan/report.c:581
 check_region_inline mm/kasan/generic.c:-1 [inline]
 kasan_check_range+0x288/0x290 mm/kasan/generic.c:187
 __asan_memcpy+0x29/0x70 mm/kasan/shadow.c:105
 leaf_paste_in_buffer+0x6a1/0xbd0 fs/reiserfs/lbalance.c:-1
 leaf_copy_dir_entries+0x5e7/0x990 fs/reiserfs/lbalance.c:108
 leaf_copy_boundary_item+0xb90/0x2180 fs/reiserfs/lbalance.c:168
 leaf_copy_items fs/reiserfs/lbalance.c:551 [inline]
 leaf_move_items+0x8b5/0xe90 fs/reiserfs/lbalance.c:726
 balance_leaf_when_delete_left fs/reiserfs/do_balan.c:167 [inline]
 balance_leaf_when_delete fs/reiserfs/do_balan.c:272 [inline]
 balance_leaf+0xc257/0x10da0 fs/reiserfs/do_balan.c:1393
 do_balance+0x2fe/0x940 fs/reiserfs/do_balan.c:1888
 reiserfs_cut_from_item+0x13b2/0x1f10 fs/reiserfs/stree.c:1836
 reiserfs_do_truncate+0xa3d/0x1340 fs/reiserfs/stree.c:1971
 reiserfs_truncate_file+0x37a/0x7c0 fs/reiserfs/inode.c:2306
 reiserfs_setattr+0xc0c/0x11a0 fs/reiserfs/inode.c:3392
 notify_change+0xb0d/0xe10 fs/attr.c:499
 do_truncate+0x19b/0x220 fs/open.c:66
 handle_truncate fs/namei.c:3291 [inline]
 do_open fs/namei.c:3636 [inline]
 path_openat+0x298c/0x3190 fs/namei.c:3789
 do_filp_open+0x1c5/0x3d0 fs/namei.c:3816
 do_sys_openat2+0x12c/0x1c0 fs/open.c:1419
 do_sys_open fs/open.c:1434 [inline]
 __do_sys_openat fs/open.c:1450 [inline]
 __se_sys_openat fs/open.c:1445 [inline]
 __x64_sys_openat+0x139/0x160 fs/open.c:1445
 do_syscall_x64 arch/x86/entry/common.c:51 [inline]
 do_syscall_64+0x55/0xb0 arch/x86/entry/common.c:81
 entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7f53fff8ebe9
Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 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 a8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f53ff5fe038 EFLAGS: 00000246 ORIG_RAX: 0000000000000101
RAX: ffffffffffffffda RBX: 00007f54001b6180 RCX: 00007f53fff8ebe9
RDX: 0000000000000300 RSI: 0000200000000080 RDI: ffffffffffffff9c
RBP: 00007f5400011e19 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f54001b6218 R14: 00007f54001b6180 R15: 00007ffd9b2d71c8
 </TASK>

The buggy address belongs to the physical page:
page:ffffea0001adc1c0 refcount:2 mapcount:0 mapping:ffff888148d00878 index:0x334 pfn:0x6b707
memcg:ffff8880785c0000
aops:def_blk_aops ino:700000
flags: 0xfff58000008234(referenced|dirty|lru|workingset|private|node=0|zone=1|lastcpupid=0x7ff)
page_type: 0xffffffff()
raw: 00fff58000008234 ffffea00017bb788 ffffea00017ac908 ffff888148d00878
raw: 0000000000000334 ffff88805f55ce80 00000002ffffffff ffff8880785c0000
page dumped because: kasan: bad access detected
page_owner tracks the page as allocated
page last allocated via order 0, migratetype Movable, gfp_mask 0x148c48(GFP_NOFS|__GFP_NOFAIL|__GFP_COMP|__GFP_HARDWALL|__GFP_MOVABLE), pid 6008, tgid 6005 (syz.0.30), ts 87763469873, free_ts 85861615908
 set_page_owner include/linux/page_owner.h:31 [inline]
 post_alloc_hook+0x1cd/0x210 mm/page_alloc.c:1554
 prep_new_page mm/page_alloc.c:1561 [inline]
 get_page_from_freelist+0x195c/0x19f0 mm/page_alloc.c:3191
 __alloc_pages+0x1e3/0x460 mm/page_alloc.c:4457
 folio_alloc+0x1e/0x30 mm/mempolicy.c:2291
 filemap_alloc_folio+0xdf/0x470 mm/filemap.c:1004
 __filemap_get_folio+0x3ee/0xbc0 mm/filemap.c:1962
 grow_dev_page fs/buffer.c:1058 [inline]
 grow_buffers fs/buffer.c:1118 [inline]
 __getblk_slow fs/buffer.c:1145 [inline]
 __getblk_gfp+0x223/0x660 fs/buffer.c:1439
 sb_getblk include/linux/buffer_head.h:344 [inline]
 get_empty_nodes+0x515/0x8c0 fs/reiserfs/fix_node.c:890
 fix_nodes+0x1e52/0x82e0 fs/reiserfs/fix_node.c:2663
 reiserfs_paste_into_item+0x5ce/0x7f0 fs/reiserfs/stree.c:2128
 reiserfs_get_block+0x1bd3/0x3ed0 fs/reiserfs/inode.c:1069
 __block_write_begin_int+0x566/0x1ad0 fs/buffer.c:2124
 reiserfs_write_begin+0x20a/0x4c0 fs/reiserfs/inode.c:2771
 generic_perform_write+0x2fb/0x5b0 mm/filemap.c:4016
 generic_file_write_iter+0xaf/0x2e0 mm/filemap.c:4137
 do_iter_readv_writev fs/read_write.c:-1 [inline]
 do_iter_write+0x79a/0xc70 fs/read_write.c:860
page last free stack trace:
 reset_page_owner include/linux/page_owner.h:24 [inline]
 free_pages_prepare mm/page_alloc.c:1154 [inline]
 free_unref_page_prepare+0x7ce/0x8e0 mm/page_alloc.c:2336
 free_unref_page_list+0xbe/0x860 mm/page_alloc.c:2475
 release_pages+0x1fa0/0x2220 mm/swap.c:1022
 __folio_batch_release+0x71/0xe0 mm/swap.c:1042
 folio_batch_release include/linux/pagevec.h:83 [inline]
 truncate_inode_pages_range+0x358/0xf00 mm/truncate.c:371
 kill_bdev block/bdev.c:76 [inline]
 blkdev_flush_mapping+0x132/0x290 block/bdev.c:632
 blkdev_put_whole block/bdev.c:663 [inline]
 blkdev_put+0x498/0x760 block/bdev.c:941
 bdev_release+0x57/0x70 block/bdev.c:951
 deactivate_locked_super+0x97/0x100 fs/super.c:481
 cleanup_mnt+0x429/0x4c0 fs/namespace.c:1250
 task_work_run+0x1ce/0x250 kernel/task_work.c:239
 resume_user_mode_work include/linux/resume_user_mode.h:49 [inline]
 exit_to_user_mode_loop+0xe6/0x110 kernel/entry/common.c:177
 exit_to_user_mode_prepare+0xb1/0x140 kernel/entry/common.c:210
 __syscall_exit_to_user_mode_work kernel/entry/common.c:291 [inline]
 syscall_exit_to_user_mode+0x1a/0x50 kernel/entry/common.c:302
 do_syscall_64+0x61/0xb0 arch/x86/entry/common.c:87
 entry_SYSCALL_64_after_hwframe+0x68/0xd2

Memory state around the buggy address:
 ffff88806b707f00: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
 ffff88806b707f80: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
>ffff88806b708000: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
                   ^
 ffff88806b708080: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff88806b708100: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
==================================================================

Crashes (22):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2025/08/12 09:45 linux-6.6.y 3a8ababb8b6a c06e8995 .config console log report syz / log C [disk image] [vmlinux] [kernel image] [mounted in repro (corrupt fs)] ci2-linux-6-6-kasan KASAN: use-after-free Read in leaf_paste_in_buffer
2025/12/20 08:00 linux-6.6.y 5fa4793a2d2d d6526ea3 .config console log report syz / log C [disk image] [vmlinux] [kernel image] [mounted in repro (corrupt fs)] ci2-linux-6-6-kasan KASAN: out-of-bounds Read in leaf_paste_in_buffer
2025/12/26 23:48 linux-6.6.y 5fa4793a2d2d d6526ea3 .config console log report syz / log [disk image] [vmlinux] [kernel image] [mounted in repro (corrupt fs)] ci2-linux-6-6-kasan KASAN: use-after-free Write in leaf_paste_in_buffer
2025/08/19 05:11 linux-6.6.y bb9c90ab9c5a 523f460e .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan KASAN: use-after-free Read in leaf_paste_in_buffer
2025/08/19 05:10 linux-6.6.y bb9c90ab9c5a 523f460e .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan KASAN: use-after-free Read in leaf_paste_in_buffer
2025/08/18 20:24 linux-6.6.y bb9c90ab9c5a 1804e95e .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan KASAN: use-after-free Read in leaf_paste_in_buffer
2025/08/18 20:23 linux-6.6.y bb9c90ab9c5a 1804e95e .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan KASAN: use-after-free Read in leaf_paste_in_buffer
2025/08/18 20:20 linux-6.6.y bb9c90ab9c5a 1804e95e .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan KASAN: use-after-free Read in leaf_paste_in_buffer
2025/08/18 20:20 linux-6.6.y bb9c90ab9c5a 1804e95e .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan KASAN: use-after-free Read in leaf_paste_in_buffer
2025/08/12 22:49 linux-6.6.y 3a8ababb8b6a 22ec1469 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan KASAN: use-after-free Read in leaf_paste_in_buffer
2025/08/12 08:41 linux-6.6.y 3a8ababb8b6a c06e8995 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan KASAN: use-after-free Read in leaf_paste_in_buffer
2025/08/12 08:37 linux-6.6.y 3a8ababb8b6a c06e8995 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan KASAN: use-after-free Read in leaf_paste_in_buffer
2025/07/09 14:00 linux-6.6.y a5df3a702b2c f4e5e155 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan KASAN: use-after-free Read in leaf_paste_in_buffer
2026/01/31 04:16 linux-6.6.y 2cf6f68313dc c75a2f6e .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan KASAN: out-of-bounds Read in leaf_paste_in_buffer
2026/01/23 16:50 linux-6.6.y cbb31f77b879 e2b1b6e6 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan KASAN: out-of-bounds Read in leaf_paste_in_buffer
2026/01/10 20:10 linux-6.6.y 5fa4793a2d2d d6526ea3 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan KASAN: out-of-bounds Read in leaf_paste_in_buffer
2026/01/04 19:54 linux-6.6.y 5fa4793a2d2d d6526ea3 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan KASAN: out-of-bounds Read in leaf_paste_in_buffer
2026/01/03 00:07 linux-6.6.y 5fa4793a2d2d d6526ea3 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan KASAN: use-after-free Write in leaf_paste_in_buffer
2026/01/03 00:06 linux-6.6.y 5fa4793a2d2d d6526ea3 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan KASAN: use-after-free Write in leaf_paste_in_buffer
2025/12/27 22:04 linux-6.6.y 5fa4793a2d2d d6526ea3 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan KASAN: out-of-bounds Read in leaf_paste_in_buffer
2025/12/20 05:59 linux-6.6.y 5fa4793a2d2d d6526ea3 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan KASAN: out-of-bounds Read in leaf_paste_in_buffer
2025/11/11 19:50 linux-6.6.y 0a805b6ea8cd 4e1406b4 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan KASAN: use-after-free Write in leaf_paste_in_buffer
* Struck through repros no longer work on HEAD.