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KASAN: null-ptr-deref Read in fix_nodes

Status: upstream: reported C repro on 2023/04/17 07:27
Bug presence: origin:upstream
Labels: missing-backport
[Documentation on labels]
Reported-by: syzbot+85ae5542a869a0e56709@syzkaller.appspotmail.com
First crash: 992d, last: 3d23h
Fix commit to backport (bisect log) :
tree: upstream
commit e0c2ff903c320d3fd3c2c604dc401b3b7c0a1d13
Author: Peter Zijlstra <peterz@infradead.org>
Date: Wed May 31 11:58:41 2023 +0000

  sched/fair: Remove sched_feat(START_DEBIT)

  
Fix bisection: the issue occurs on the latest tested release (bisect log)
Crash: KASAN: null-ptr-deref Read in fix_nodes (log)
Repro: C syz .config
  
▶ ▼ Bug presence (3)
Date Name Commit Repro Result
2023/10/16 linux-6.1.y (ToT) adc4d740ad9e C [report] KASAN: null-ptr-deref Read in fix_nodes
2023/06/03 upstream (ToT) 4ecd704a4c51 C [report] KASAN: null-ptr-deref Read in fix_nodes
2023/10/16 upstream (ToT) 58720809f527 C Didn't crash
▶ ▼ Similar bugs (4)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
upstream KASAN: null-ptr-deref Read in fix_nodes fs 11 C done done 17 729d 998d 0/29 auto-obsoleted due to no activity on 2024/04/13 10:42
linux-5.15 KASAN: null-ptr-deref Read in fix_nodes missing-backport origin:upstream 11 C done 12 22d 993d 0/3 upstream: reported C repro on 2023/04/15 23:10
linux-4.19 general protection fault in fix_nodes 2 C error 1 1121d 1121d 0/1 upstream: reported C repro on 2022/12/08 10:03
linux-4.14 general protection fault in fix_nodes 2 syz error 1 1115d 1115d 0/1 upstream: reported syz repro on 2022/12/15 05:04
▶ ▼ Fix bisection attempts (4)
Created Duration User Patch Repo Result
2024/01/05 16:15 6h26m fix candidate upstream OK (1) job log
2023/12/31 23:55 2h09m bisect fix linux-6.1.y OK (0) job log log
2023/12/01 17:27 2h12m bisect fix linux-6.1.y OK (0) job log log
2023/09/19 02:31 2h12m bisect fix linux-6.1.y OK (0) job log log

Sample crash report:
==================================================================
BUG: KASAN: null-ptr-deref in instrument_atomic_read include/linux/instrumented.h:72 [inline]
BUG: KASAN: null-ptr-deref in _test_bit include/asm-generic/bitops/instrumented-non-atomic.h:141 [inline]
BUG: KASAN: null-ptr-deref in buffer_locked include/linux/buffer_head.h:123 [inline]
BUG: KASAN: null-ptr-deref in fix_nodes+0x435/0x82d0 fs/reiserfs/fix_node.c:2578
Read of size 8 at addr 0000000000000000 by task syz.1.71/4698

CPU: 0 PID: 4698 Comm: syz.1.71 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025
Call Trace:
 <TASK>
 dump_stack_lvl+0x168/0x22e lib/dump_stack.c:106
 kasan_report+0x10b/0x140 mm/kasan/report.c:524
 check_region_inline mm/kasan/generic.c:-1 [inline]
 kasan_check_range+0x27b/0x290 mm/kasan/generic.c:189
 instrument_atomic_read include/linux/instrumented.h:72 [inline]
 _test_bit include/asm-generic/bitops/instrumented-non-atomic.h:141 [inline]
 buffer_locked include/linux/buffer_head.h:123 [inline]
 fix_nodes+0x435/0x82d0 fs/reiserfs/fix_node.c:2578
 reiserfs_cut_from_item+0x2e8/0x1ef0 fs/reiserfs/stree.c:1742
 reiserfs_do_truncate+0xa90/0x13e0 fs/reiserfs/stree.c:1973
 reiserfs_truncate_file+0x376/0x7c0 fs/reiserfs/inode.c:2310
 reiserfs_setattr+0xcae/0x1240 fs/reiserfs/inode.c:3395
 notify_change+0xc74/0xf40 fs/attr.c:499
 do_truncate+0x197/0x220 fs/open.c:65
 handle_truncate fs/namei.c:3293 [inline]
 do_open fs/namei.c:3638 [inline]
 path_openat+0x27f2/0x2e70 fs/namei.c:3791
 do_filp_open+0x1c1/0x3c0 fs/namei.c:3818
 do_sys_openat2+0x142/0x490 fs/open.c:1320
 do_sys_open fs/open.c:1336 [inline]
 __do_sys_openat fs/open.c:1352 [inline]
 __se_sys_openat fs/open.c:1347 [inline]
 __x64_sys_openat+0x135/0x160 fs/open.c:1347
 do_syscall_x64 arch/x86/entry/common.c:51 [inline]
 do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:81
 entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7f2ebcd8f749
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:00007f2ebdbdc038 EFLAGS: 00000246 ORIG_RAX: 0000000000000101
RAX: ffffffffffffffda RBX: 00007f2ebcfe5fa0 RCX: 00007f2ebcd8f749
RDX: 0000000000103a42 RSI: 0000200000000380 RDI: ffffffffffffff9c
RBP: 00007f2ebce13f91 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f2ebcfe6038 R14: 00007f2ebcfe5fa0 R15: 00007ffdb8933b98
 </TASK>
==================================================================

Crashes (11):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2025/12/24 21:29 linux-6.1.y 50cbba13faa2 d6526ea3 .config console log report syz / log C [disk image] [vmlinux] [kernel image] [mounted in repro (corrupt fs)] ci2-linux-6-1-kasan KASAN: null-ptr-deref Read in fix_nodes
2023/06/03 08:07 linux-6.1.y d2869ace6eeb a4ae4f42 .config console log report syz C [disk image] [vmlinux] [kernel image] [mounted in repro] ci2-linux-6-1-kasan KASAN: null-ptr-deref Read in fix_nodes
2025/12/30 09:47 linux-6.1.y 50cbba13faa2 d6526ea3 .config console log report syz / log [disk image] [vmlinux] [kernel image] [mounted in repro (corrupt fs)] ci2-linux-6-1-kasan KASAN: null-ptr-deref Read in fix_nodes
2025/12/09 00:25 linux-6.1.y 50cbba13faa2 d6526ea3 .config console log report syz / log [disk image] [vmlinux] [kernel image] [mounted in repro (corrupt fs)] ci2-linux-6-1-kasan KASAN: null-ptr-deref Read in fix_nodes
2024/08/13 01:33 linux-6.1.y 36790ef5e00b 7b0f4b46 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan KASAN: null-ptr-deref Read in fix_nodes
2024/06/07 01:03 linux-6.1.y 88690811da69 121701b6 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan KASAN: null-ptr-deref Read in fix_nodes
2023/10/31 10:05 linux-6.1.y 32c9cdbe383c b5729d82 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan KASAN: null-ptr-deref Read in fix_nodes
2023/10/22 06:15 linux-6.1.y 7d24402875c7 361b23dc .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan KASAN: null-ptr-deref Read in fix_nodes
2023/06/28 18:06 linux-6.1.y a1c449d00ff8 ca69c785 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan KASAN: null-ptr-deref Read in fix_nodes
2023/04/17 07:27 linux-6.1.y 0102425ac76b ec410564 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan KASAN: null-ptr-deref Read in fix_nodes
2023/07/05 05:21 linux-6.1.y 0f4ac6b4c5f0 80298b6f .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-arm64 BUG: unable to handle kernel paging request in fix_nodes
* Struck through repros no longer work on HEAD.