KASAN: use-after-free Read in __ext4_check_dir_entry

Status: closed as dup on 2018/03/31 22:38
Subsystems: ext4
[Documentation on labels]
Reported-by: syzbot+1236ce66f79263e8a862@syzkaller.appspotmail.com
Fix commit: e40ff2138985 ext4: force revalidation of directory pointer after seekdir(2)
First crash: 3050d, last: 3047d
▶ ▼ Duplicate of
Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported
KASAN: slab-out-of-bounds Read in __ext4_check_dir_entry ext4 17 syz, C 18 3049d 3049d
▶ ▼ Discussions (4)
Title Replies (including bot) Last reply
[PATCH 3.16 000/366] 3.16.60-rc1 review 370 (370) 2019/03/29 15:47
[PATCH 4.16 000/196] 4.16.4-stable review 213 (213) 2018/04/28 14:59
KASAN: use-after-free Read in __ext4_check_dir_entry 0 (1) 2018/03/31 20:47
KASAN: use-after-free Read in __ext4_check_dir_entry 0 (1) 2018/03/31 20:47
▶ ▼ Similar bugs (13)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
android-5-10 KASAN: use-after-free Read in __ext4_check_dir_entry (2) 19 syz, C 12 1d15h 564d 0/2 upstream: reported C repro on 2025/01/19 16:52
upstream KASAN: use-after-free Read in __ext4_check_dir_entry (3) ext4 19 syz, C inconclusive done 6 516d 669d 0/29 auto-obsoleted due to no activity on 2025/06/16 07:57
linux-4.14 KASAN: use-after-free Read in __ext4_check_dir_entry 19 syz, C inconclusive 6 2143d 2246d 0/1 upstream: reported C repro on 2020/06/12 02:23
upstream KASAN: use-after-free Read in __ext4_check_dir_entry (2) ext4 19 syz, C error 1 804d 814d 0/29 closed as dup on 2024/06/26 08:39
android-5-15 KASAN: use-after-free Read in __ext4_check_dir_entry (2) origin:lts 19 syz, C error 11 3h08m 484d 0/2 upstream: reported C repro on 2025/04/09 15:24
linux-5.15 KASAN: use-after-free Read in __ext4_check_dir_entry origin:upstream 19 syz, C error 10 72d 794d 0/3 upstream: reported C repro on 2024/06/03 01:15
android-5-15 KASAN: use-after-free Read in __ext4_check_dir_entry missing-backport origin:upstream 19 syz, C error 4 645d 769d 0/2 auto-obsoleted due to no activity on 2025/02/07 07:57
linux-6.6 KASAN: use-after-free Read in __ext4_check_dir_entry origin:upstream 19 syz, C error 1 165d 165d 0/2 upstream: reported C repro on 2026/02/22 03:13
upstream KASAN: slab-use-after-free Read in __ext4_check_dir_entry prio:high ext4 19 syz, C error error 6 46d 402d 1/29 upstream: reported C repro on 2025/06/30 17:28
android-5-10 KASAN: use-after-free Read in __ext4_check_dir_entry 19 syz, C error 2 700d 818d 0/2 auto-obsoleted due to no activity on 2024/12/26 18:56
android-6-1 KASAN: use-after-free Read in __ext4_check_dir_entry missing-backport origin:upstream 19 syz, C error 4 693d 817d 0/2 auto-obsoleted due to no activity on 2024/12/21 14:06
linux-6.1 KASAN: use-after-free Read in __ext4_check_dir_entry 19 15 757d 794d 0/3 auto-obsoleted due to no activity on 2024/09/17 20:54
android-6-1 KASAN: use-after-free Read in __ext4_check_dir_entry (2) origin:upstream 19 syz, C error 9 62d 488d 0/2 upstream: reported C repro on 2025/04/05 13:22

Sample crash report:
==================================================================
BUG: KASAN: use-after-free in __ext4_check_dir_entry+0x2de/0x320 fs/ext4/dir.c:69
Read of size 2 at addr ffff8801b80bf000 by task syzkaller432828/4365

CPU: 1 PID: 4365 Comm: syzkaller432828 Not tainted 4.16.0-rc7+ #7
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
 __dump_stack lib/dump_stack.c:17 [inline]
 dump_stack+0x194/0x24d lib/dump_stack.c:53
 print_address_description+0x73/0x250 mm/kasan/report.c:256
 kasan_report_error mm/kasan/report.c:354 [inline]
 kasan_report+0x23c/0x360 mm/kasan/report.c:412
 __asan_report_load2_noabort+0x14/0x20 mm/kasan/report.c:431
 __ext4_check_dir_entry+0x2de/0x320 fs/ext4/dir.c:69
 ext4_readdir+0xd00/0x3600 fs/ext4/dir.c:237
 iterate_dir+0x1ca/0x530 fs/readdir.c:51
 SYSC_getdents64 fs/readdir.c:314 [inline]
 SyS_getdents64+0x221/0x420 fs/readdir.c:295
 do_syscall_64+0x281/0x940 arch/x86/entry/common.c:287
 entry_SYSCALL_64_after_hwframe+0x42/0xb7
RIP: 0033:0x43fd69
RSP: 002b:00007ffc446ac118 EFLAGS: 00000203 ORIG_RAX: 00000000000000d9
RAX: ffffffffffffffda RBX: 00000000004002c8 RCX: 000000000043fd69
RDX: 00000000200015fc RSI: 0000000020001540 RDI: 0000000000000003
RBP: 00000000006ca018 R08: 00000000004002c8 R09: 00000000004002c8
R10: 00000000004002c8 R11: 0000000000000203 R12: 0000000000401690
R13: 0000000000401720 R14: 0000000000000000 R15: 0000000000000000

The buggy address belongs to the page:
page:ffffea0006e02fc0 count:0 mapcount:0 mapping:0000000000000000 index:0x0
flags: 0x2fffc0000000000()
raw: 02fffc0000000000 0000000000000000 0000000000000000 00000000ffffffff
raw: ffffea0006c095a0 ffffea0006e03020 ffff8801be5f2a50 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff8801b80bef00: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
 ffff8801b80bef80: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
>ffff8801b80bf000: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
                   ^
 ffff8801b80bf080: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff8801b80bf100: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
==================================================================

Crashes (8):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2018/03/31 05:05 upstream 9dd2326890d8 8fbce0e4 .config console log report syz C ci-upstream-kasan-gce-root
2018/04/03 12:17 upstream 642e7fd23353 676bd07e .config console log report ci-upstream-kasan-gce-root
2018/04/01 11:07 upstream 10b84daddbec 0174c6c8 .config console log report ci-upstream-kasan-gce-root
2018/04/01 07:39 upstream 10b84daddbec 0174c6c8 .config console log report ci-upstream-kasan-gce-root
2018/04/01 07:30 upstream 10b84daddbec 0174c6c8 .config console log report ci-upstream-kasan-gce-root
2018/04/01 06:13 upstream 10b84daddbec 0174c6c8 .config console log report ci-upstream-kasan-gce-root
2018/04/01 02:19 upstream 10b84daddbec 0174c6c8 .config console log report ci-upstream-kasan-gce-root
2018/04/01 02:15 upstream 10b84daddbec 0174c6c8 .config console log report ci-upstream-kasan-gce-root
* Struck through repros no longer work on HEAD.