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KASAN: use-after-free Read in ext4_find_extent (2)

Status: upstream: reported C repro on 2025/05/31 08:45
Bug presence: origin:lts
[Documentation on labels]
Reported-by: syzbot+869401e856e234844286@syzkaller.appspotmail.com
First crash: 318d, last: 5d00h
▶ ▼ Bug presence (2)
Date Name Commit Repro Result
2025/06/01 lts (merge base) 02b72ccb5f9d C [report] KASAN: use-after-free Read in ext4_find_extent
2025/06/01 upstream (ToT) cd2e103d57e5 C Didn't crash
▶ ▼ Similar bugs (12)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
android-54 KASAN: use-after-free Read in ext4_find_extent 19 C 2 327d 425d 0/2 upstream: reported C repro on 2025/02/13 21:05
android-5-10 KASAN: use-after-free Read in ext4_find_extent ext4 19 C error inconclusive 115 7d13h 1205d 0/2 upstream: reported C repro on 2022/12/26 07:59
android-6-1 KASAN: use-after-free Read in ext4_find_extent missing-backport 19 C error done 3 534d 1031d 0/2 auto-obsoleted due to no activity on 2025/02/04 04:57
linux-5.15 KASAN: use-after-free Read in ext4_find_extent origin:lts-only 19 C inconclusive 7 41d 1000d 0/3 upstream: reported C repro on 2023/07/19 14:49
linux-6.6 KASAN: use-after-free Read in ext4_find_extent 19 C error 8 109d 110d 0/2 upstream: reported C repro on 2025/12/25 19:30
upstream KASAN: use-after-free Read in ext4_find_extent ext4 19 2 1637d 1698d 0/29 auto-closed as invalid on 2022/02/17 05:19
linux-6.1 KASAN: use-after-free Read in ext4_find_extent origin:upstream missing-backport 19 C done 69 18d 938d 0/3 upstream: reported C repro on 2023/09/19 00:11
android-5-15 KASAN: use-after-free Read in ext4_find_extent ext4 origin:lts 19 C error 124 7d00h 1205d 0/2 upstream: reported C repro on 2022/12/26 07:59
upstream KASAN: use-after-free Read in ext4_find_extent (2) ext4 19 C error 2 1075d 1200d 22/29 fixed on 2023/06/08 14:41
upstream KASAN: use-after-free Read in ext4_find_extent (4) ext4 19 C done 307 16d 470d 0/29 upstream: reported C repro on 2024/12/30 20:06
upstream KASAN: use-after-free Read in ext4_find_extent (3) prio:low ext4 19 C error done 31 840d 1022d 25/29 fixed on 2024/01/30 23:26
android-54 KASAN: slab-out-of-bounds Read in ext4_find_extent ext4 17 C 1 1019d 1205d 0/2 auto-obsoleted due to no activity on 2023/10/08 03:20
▶ ▼ Last patch testing requests (9)
Created Duration User Patch Repo Result
2026/04/09 20:02 7m retest repro android14-6.1 report log
2026/04/09 20:02 6m retest repro android14-6.1 report log
2026/04/09 20:02 7m retest repro android14-6.1 report log
2026/04/09 20:02 16m retest repro android14-6.1 report log
2026/04/09 20:02 12m retest repro android14-6.1 report log
2026/03/23 08:39 8m retest repro android14-6.1 report log
2026/03/23 08:39 7m retest repro android14-6.1 report log
2026/03/23 08:39 6m retest repro android14-6.1 report log
2026/03/23 08:39 9m retest repro android14-6.1 report log
▶ ▼ Fix bisection attempts (2)
Created Duration User Patch Repo Result
2025/07/31 06:27 1h21m bisect fix android14-6.1 OK (0) job log log
2025/06/30 20:17 1h08m bisect fix android14-6.1 OK (0) job log log

Sample crash report:
WARNING: The mand mount option has been deprecated and
         and is ignored by this kernel. Remove the mand
         option from the mount to silence this warning.
=======================================================
EXT4-fs: Ignoring removed oldalloc option
EXT4-fs: Ignoring removed orlov option
EXT4-fs (loop2): mounted filesystem without journal. Quota mode: writeback.
==================================================================
BUG: KASAN: use-after-free in ext4_ext_binsearch fs/ext4/extents.c:837 [inline]
BUG: KASAN: use-after-free in ext4_find_extent+0xbeb/0xe20 fs/ext4/extents.c:953
Read of size 4 at addr ffff88812fa1a018 by task syz.2.17/362

CPU: 0 PID: 362 Comm: syz.2.17 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2026
Call Trace:
 <TASK>
 __dump_stack+0x21/0x24 lib/dump_stack.c:88
 dump_stack_lvl+0x110/0x170 lib/dump_stack.c:106
 print_address_description+0x71/0x200 mm/kasan/report.c:316
 print_report+0x4a/0x60 mm/kasan/report.c:420
 kasan_report+0x122/0x150 mm/kasan/report.c:524
 __asan_report_load4_noabort+0x14/0x20 mm/kasan/report_generic.c:350
 ext4_ext_binsearch fs/ext4/extents.c:837 [inline]
 ext4_find_extent+0xbeb/0xe20 fs/ext4/extents.c:953
 ext4_ext_remove_space+0x2de/0x40d0 fs/ext4/extents.c:2834
 ext4_punch_hole+0x77c/0xbd0 fs/ext4/inode.c:4147
 ext4_fallocate+0x2b6/0x1dc0 fs/ext4/extents.c:4767
 vfs_fallocate+0x4c5/0x5a0 fs/open.c:324
 ioctl_preallocate fs/ioctl.c:290 [inline]
 file_ioctl fs/ioctl.c:333 [inline]
 do_vfs_ioctl+0x19cb/0x1cd0 fs/ioctl.c:849
 __do_sys_ioctl fs/ioctl.c:868 [inline]
 __se_sys_ioctl+0x9f/0x1b0 fs/ioctl.c:856
 __x64_sys_ioctl+0x7b/0x90 fs/ioctl.c:856
 x64_sys_call+0x58b/0x9a0 arch/x86/include/generated/asm/syscalls_64.h:17
 do_syscall_x64 arch/x86/entry/common.c:46 [inline]
 do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:76
 entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7fed5259c799
Code: ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 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 e8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007ffd9d148998 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00007fed52815fa0 RCX: 00007fed5259c799
RDX: 00002000000000c0 RSI: 0000000040305829 RDI: 0000000000000005
RBP: 00007fed52632c99 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fed52815fac R14: 00007fed52815fa0 R15: 00007fed52815fa0
 </TASK>

The buggy address belongs to the physical page:
page:ffffea0004be8680 refcount:0 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x12fa1a
flags: 0x4000000000000000(zone=1)
raw: 4000000000000000 ffffea0004be8688 ffffea0004be8688 0000000000000000
raw: 0000000000000000 0000000000000000 00000000ffffffff 0000000000000000
page dumped because: kasan: bad access detected
page_owner info is not present (never set?)

Memory state around the buggy address:
 ffff88812fa19f00: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff88812fa19f80: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
>ffff88812fa1a000: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
                            ^
 ffff88812fa1a080: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff88812fa1a100: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
==================================================================
------------[ cut here ]------------
kernel BUG at fs/ext4/extents.c:3190!
invalid opcode: 0000 [#1] PREEMPT SMP KASAN
CPU: 0 PID: 362 Comm: syz.2.17 Tainted: G    B              syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2026
RIP: 0010:ext4_split_extent_at+0xf62/0xf80 fs/ext4/extents.c:3190
Code: ff ff 44 89 f1 80 e1 07 fe c1 38 c1 0f 8c 3f fb ff ff 4c 89 f7 49 89 f7 e8 9b b7 cf ff 4c 89 fe e9 2c fb ff ff e8 4e 7b 8a ff <0f> 0b e8 47 7b 8a ff 0f 0b e8 40 7b 8a ff 0f 0b e8 39 7b 8a ff 0f
RSP: 0018:ffffc900007a74c0 EFLAGS: 00010293
RAX: ffffffff81e6f382 RBX: 0000000000000000 RCX: ffff8881130b0000
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000041
RBP: ffffc900007a7630 R08: 0000000000000000 R09: 0000000050000028
R10: dffffc0000000000 R11: fffffbfff0f6e4fd R12: dffffc0000000000
R13: 0000000000000000 R14: 0000000000000000 R15: ffff8881149b1100
FS:  000055556dd21500(0000) GS:ffff8881f6e00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 000020000000f000 CR3: 000000010ed76000 CR4: 00000000003506b0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 <TASK>
 ext4_force_split_extent_at fs/ext4/extents.c:338 [inline]
 ext4_ext_remove_space+0x652/0x40d0 fs/ext4/extents.c:2881
 ext4_punch_hole+0x77c/0xbd0 fs/ext4/inode.c:4147
 ext4_fallocate+0x2b6/0x1dc0 fs/ext4/extents.c:4767
 vfs_fallocate+0x4c5/0x5a0 fs/open.c:324
 ioctl_preallocate fs/ioctl.c:290 [inline]
 file_ioctl fs/ioctl.c:333 [inline]
 do_vfs_ioctl+0x19cb/0x1cd0 fs/ioctl.c:849
 __do_sys_ioctl fs/ioctl.c:868 [inline]
 __se_sys_ioctl+0x9f/0x1b0 fs/ioctl.c:856
 __x64_sys_ioctl+0x7b/0x90 fs/ioctl.c:856
 x64_sys_call+0x58b/0x9a0 arch/x86/include/generated/asm/syscalls_64.h:17
 do_syscall_x64 arch/x86/entry/common.c:46 [inline]
 do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:76
 entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7fed5259c799
Code: ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 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 e8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007ffd9d148998 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00007fed52815fa0 RCX: 00007fed5259c799
RDX: 00002000000000c0 RSI: 0000000040305829 RDI: 0000000000000005
RBP: 00007fed52632c99 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fed52815fac R14: 00007fed52815fa0 R15: 00007fed52815fa0
 </TASK>
Modules linked in:
---[ end trace 0000000000000000 ]---
RIP: 0010:ext4_split_extent_at+0xf62/0xf80 fs/ext4/extents.c:3190
Code: ff ff 44 89 f1 80 e1 07 fe c1 38 c1 0f 8c 3f fb ff ff 4c 89 f7 49 89 f7 e8 9b b7 cf ff 4c 89 fe e9 2c fb ff ff e8 4e 7b 8a ff <0f> 0b e8 47 7b 8a ff 0f 0b e8 40 7b 8a ff 0f 0b e8 39 7b 8a ff 0f
RSP: 0018:ffffc900007a74c0 EFLAGS: 00010293
RAX: ffffffff81e6f382 RBX: 0000000000000000 RCX: ffff8881130b0000
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000041
RBP: ffffc900007a7630 R08: 0000000000000000 R09: 0000000050000028
R10: dffffc0000000000 R11: fffffbfff0f6e4fd R12: dffffc0000000000
R13: 0000000000000000 R14: 0000000000000000 R15: ffff8881149b1100
FS:  000055556dd21500(0000) GS:ffff8881f6f00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007fc50ba1f000 CR3: 000000010ed76000 CR4: 00000000003506a0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400

Crashes (32):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/03/26 18:36 android14-6.1 c0665c721df9 766b6434 .config console log report syz / log C [disk image] [vmlinux] [kernel image] [mounted in repro (corrupt fs)] ci2-android-6-1 KASAN: use-after-free Read in ext4_find_extent
2026/02/26 16:51 android14-6.1 6bfa51973214 ffa54287 .config console log report syz / log C [disk image] [vmlinux] [kernel image] [mounted in repro (corrupt fs)] ci2-android-6-1 KASAN: use-after-free Read in ext4_find_extent
2026/02/23 16:46 android14-6.1 34c1a8e17200 6beca497 .config console log report syz / log C [disk image] [vmlinux] [kernel image] [mounted in repro (corrupt fs)] ci2-android-6-1 KASAN: use-after-free Read in ext4_find_extent
2026/02/16 11:10 android14-6.1 edbe3e111301 1e62d198 .config console log report syz / log C [disk image] [vmlinux] [kernel image] [mounted in repro (corrupt fs)] ci2-android-6-1 KASAN: use-after-free Read in ext4_find_extent
2026/02/15 18:42 android14-6.1 edbe3e111301 1e62d198 .config console log report syz / log C [disk image] [vmlinux] [kernel image] [mounted in repro (corrupt fs)] ci2-android-6-1 KASAN: use-after-free Read in ext4_find_extent
2026/02/05 08:55 android14-6.1 775f23d50ca8 ea10c935 .config console log report syz / log C [disk image] [vmlinux] [kernel image] [mounted in repro (corrupt fs)] ci2-android-6-1 KASAN: use-after-free Read in ext4_find_extent
2026/01/17 19:05 android14-6.1 f8a5ad1fcf13 20d37d28 .config console log report syz / log C [disk image] [vmlinux] [kernel image] [mounted in repro (corrupt fs)] ci2-android-6-1 KASAN: use-after-free Read in ext4_find_extent
2025/10/24 04:04 android14-6.1 22c0b7236c43 c0460fcd .config console log report syz / log C [disk image] [vmlinux] [kernel image] [mounted in repro (corrupt fs)] ci2-android-6-1 KASAN: use-after-free Read in ext4_find_extent
2025/10/24 03:23 android14-6.1 22c0b7236c43 c0460fcd .config console log report syz / log C [disk image] [vmlinux] [kernel image] [mounted in repro (corrupt fs)] ci2-android-6-1 KASAN: use-after-free Read in ext4_find_extent
2025/10/24 02:37 android14-6.1 22c0b7236c43 c0460fcd .config console log report syz / log C [disk image] [vmlinux] [kernel image] [mounted in repro (corrupt fs)] ci2-android-6-1 KASAN: use-after-free Read in ext4_find_extent
2025/09/29 02:17 android14-6.1 5303560ee8cf 001c9061 .config console log report syz / log C [disk image] [vmlinux] [kernel image] [mounted in repro (corrupt fs)] ci2-android-6-1 KASAN: use-after-free Read in ext4_find_extent
2025/09/03 14:52 android14-6.1 79ccb6ecf51e 96a211bc .config console log report syz / log C [disk image] [vmlinux] [kernel image] [mounted in repro (corrupt fs)] ci2-android-6-1 KASAN: use-after-free Read in ext4_find_extent
2025/08/03 17:31 android14-6.1 3b4ff5af8d36 7368264b .config strace log report syz / log C [disk image] [vmlinux] [kernel image] [mounted in repro (corrupt fs)] ci2-android-6-1 KASAN: use-after-free Read in ext4_find_extent
2025/05/31 08:37 android14-6.1 db710ea87c32 3d2f584d .config strace log report syz / log C [disk image] [vmlinux] [kernel image] [mounted in repro (corrupt fs)] ci2-android-6-1 KASAN: use-after-free Read in ext4_find_extent
2025/11/22 21:09 android14-6.1 eba111621724 4fb8ef37 .config console log report syz / log [disk image] [vmlinux] [kernel image] [mounted in repro (clean fs)] ci2-android-6-1 KASAN: use-after-free Read in ext4_find_extent
2026/03/26 18:05 android14-6.1 c0665c721df9 766b6434 .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-6-1 KASAN: use-after-free Read in ext4_find_extent
2026/03/08 15:12 android14-6.1 6bfa51973214 5cb44a80 .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-6-1 KASAN: use-after-free Read in ext4_find_extent
2026/02/20 15:56 android14-6.1 edbe3e111301 17d780d6 .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-6-1 KASAN: use-after-free Read in ext4_find_extent
2026/02/12 06:48 android14-6.1 edbe3e111301 76a109e2 .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-6-1 KASAN: use-after-free Read in ext4_find_extent
2026/02/12 06:48 android14-6.1 edbe3e111301 76a109e2 .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-6-1 KASAN: use-after-free Read in ext4_find_extent
2025/12/30 18:59 android14-6.1 5e6db7045704 d6526ea3 .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-6-1 KASAN: use-after-free Read in ext4_find_extent
2025/12/30 18:59 android14-6.1 5e6db7045704 d6526ea3 .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-6-1 KASAN: use-after-free Read in ext4_find_extent
2025/12/30 18:58 android14-6.1 5e6db7045704 d6526ea3 .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-6-1 KASAN: use-after-free Read in ext4_find_extent
2025/12/30 18:57 android14-6.1 5e6db7045704 d6526ea3 .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-6-1 KASAN: use-after-free Read in ext4_find_extent
2025/12/01 12:36 android14-6.1 a92da54b7708 d6526ea3 .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-6-1 KASAN: use-after-free Read in ext4_find_extent
2025/11/30 15:55 android14-6.1 a92da54b7708 d6526ea3 .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-6-1 KASAN: use-after-free Read in ext4_find_extent
2025/09/14 09:34 android14-6.1 0429b7af308c e2beed91 .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-6-1 KASAN: use-after-free Read in ext4_find_extent
2025/08/28 01:48 android14-6.1 47b374a18638 e12e5ba4 .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-6-1 KASAN: use-after-free Read in ext4_find_extent
2025/08/28 01:48 android14-6.1 47b374a18638 e12e5ba4 .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-6-1 KASAN: use-after-free Read in ext4_find_extent
2025/08/28 01:46 android14-6.1 47b374a18638 e12e5ba4 .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-6-1 KASAN: use-after-free Read in ext4_find_extent
2025/08/28 01:46 android14-6.1 47b374a18638 e12e5ba4 .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-6-1 KASAN: use-after-free Read in ext4_find_extent
2025/05/31 08:03 android14-6.1 db710ea87c32 3d2f584d .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-6-1 KASAN: use-after-free Read in ext4_find_extent
* Struck through repros no longer work on HEAD.