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kernel BUG in ext4_swap_extents

Status: upstream: reported C repro on 2025/12/08 08:03
Subsystems: ext4
[Documentation on labels]
Reported-by: syzbot+4ea6bd8737669b423aae@syzkaller.appspotmail.com
Fix commit: ext4: add missing down_write_data_sem in mext_move_extent().
Patched on: [ci-upstream-linux-next-kasan-gce-root ci-upstream-rust-kasan-gce], missing on: [ci-qemu-gce-upstream-auto ci-qemu-native-arm64-kvm ci-qemu-upstream ci-qemu-upstream-386 ci-qemu2-arm32 ci-qemu2-arm64 ci-qemu2-arm64-compat ci-qemu2-arm64-mte ci-qemu2-riscv64 ci-snapshot-upstream-root ci-upstream-bpf-kasan-gce ci-upstream-bpf-next-kasan-gce ci-upstream-gce-arm64 ci-upstream-gce-leak ci-upstream-kasan-badwrites-root ci-upstream-kasan-gce ci-upstream-kasan-gce-386 ci-upstream-kasan-gce-root ci-upstream-kasan-gce-selinux-root ci-upstream-kasan-gce-smack-root ci-upstream-kmsan-gce-386-root ci-upstream-kmsan-gce-root ci-upstream-net-kasan-gce ci-upstream-net-this-kasan-gce ci2-upstream-fs ci2-upstream-kcsan-gce ci2-upstream-usb]
First crash: 40d, last: 25d
▶ ▼ Discussions (2)
Title Replies (including bot) Last reply
[PATCH] ext4: add missing down_write_data_sem in mext_move_extent(). 4 (4) 2025/12/09 08:22
[syzbot] [ext4?] kernel BUG in ext4_swap_extents 0 (2) 2025/12/08 12:45
▶ ▼ Last patch testing requests (3)
Created Duration User Patch Repo Result
2025/12/20 04:53 14m retest repro upstream error
2025/12/20 04:53 20m retest repro upstream OK log
2025/12/08 12:45 21m kartikey406@gmail.com patch upstream OK log

Sample crash report:
------------[ cut here ]------------
kernel BUG at fs/ext4/extents.c:5683!
Oops: invalid opcode: 0000 [#1] SMP KASAN NOPTI
CPU: 0 UID: 0 PID: 5528 Comm: syz.0.24 Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2~bpo12+1 04/01/2014
RIP: 0010:ext4_swap_extents+0x196c/0x19a0 fs/ext4/extents.c:5683
Code: fe c1 38 c1 0f 8c 7e fe ff ff e8 1f 17 b3 ff e9 74 fe ff ff e8 b5 79 4b ff 90 0f 0b e8 ad 79 4b ff 90 0f 0b e8 a5 79 4b ff 90 <0f> 0b e8 9d 79 4b ff 90 0f 0b e8 95 79 4b ff 90 0f 0b e8 8d 79 4b
RSP: 0018:ffffc9000cc0f2c0 EFLAGS: 00010293
RAX: ffffffff8275e17b RBX: 0000000000000000 RCX: ffff88801fb324c0
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000000
RBP: dffffc0000000000 R08: ffff888042379547 R09: 1ffff1100846f2a8
R10: dffffc0000000000 R11: ffffed100846f2a9 R12: 0000000000000001
R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000001
FS:  00007fed9d1f96c0(0000) GS:ffff88808d683000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000001b30863fff CR3: 0000000000731000 CR4: 0000000000352ef0
Call Trace:
 <TASK>
 mext_move_extent fs/ext4/move_extent.c:396 [inline]
 ext4_move_extents+0x2c58/0x3830 fs/ext4/move_extent.c:616
 __ext4_ioctl fs/ext4/ioctl.c:1652 [inline]
 ext4_ioctl+0x2cf9/0x4760 fs/ext4/ioctl.c:1917
 vfs_ioctl fs/ioctl.c:51 [inline]
 __do_sys_ioctl fs/ioctl.c:597 [inline]
 __se_sys_ioctl+0xfc/0x170 fs/ioctl.c:583
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xfa/0xf80 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7fed9c38f7c9
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:00007fed9d1f9038 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00007fed9c5e5fa0 RCX: 00007fed9c38f7c9
RDX: 0000200000000080 RSI: 00000000c028660f RDI: 0000000000000005
RBP: 00007fed9d1f9090 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000002
R13: 00007fed9c5e6038 R14: 00007fed9c5e5fa0 R15: 00007fffbb119b38
 </TASK>
Modules linked in:
---[ end trace 0000000000000000 ]---
RIP: 0010:ext4_swap_extents+0x196c/0x19a0 fs/ext4/extents.c:5683
Code: fe c1 38 c1 0f 8c 7e fe ff ff e8 1f 17 b3 ff e9 74 fe ff ff e8 b5 79 4b ff 90 0f 0b e8 ad 79 4b ff 90 0f 0b e8 a5 79 4b ff 90 <0f> 0b e8 9d 79 4b ff 90 0f 0b e8 95 79 4b ff 90 0f 0b e8 8d 79 4b
RSP: 0018:ffffc9000cc0f2c0 EFLAGS: 00010293
RAX: ffffffff8275e17b RBX: 0000000000000000 RCX: ffff88801fb324c0
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000000
RBP: dffffc0000000000 R08: ffff888042379547 R09: 1ffff1100846f2a8
R10: dffffc0000000000 R11: ffffed100846f2a9 R12: 0000000000000001
R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000001
FS:  00007fed9d1f96c0(0000) GS:ffff88808d683000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000001b30863fff CR3: 0000000000731000 CR4: 0000000000352ef0

Crashes (5):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2025/12/06 04:53 upstream d1d36025a617 d1b870e1 .config console log report syz / log C [disk image (non-bootable)] [vmlinux] [kernel image] [mounted in repro (clean fs)] ci-snapshot-upstream-root kernel BUG in ext4_swap_extents
2025/12/21 11:37 upstream 9094662f6707 d1b870e1 .config console log report [disk image (non-bootable)] [vmlinux] [kernel image] ci-snapshot-upstream-root kernel BUG in ext4_swap_extents
2025/12/06 04:22 upstream d1d36025a617 d1b870e1 .config console log report syz / log C [disk image (non-bootable)] [vmlinux] [kernel image] [mounted in repro (clean fs)] ci-snapshot-upstream-root kernel BUG in ext4_swap_extents
2025/12/06 02:19 upstream d1d36025a617 d1b870e1 .config console log report [disk image (non-bootable)] [vmlinux] [kernel image] ci-snapshot-upstream-root kernel BUG in ext4_swap_extents
2025/12/06 02:19 upstream d1d36025a617 d1b870e1 .config console log report [disk image (non-bootable)] [vmlinux] [kernel image] ci-snapshot-upstream-root kernel BUG in ext4_swap_extents
* Struck through repros no longer work on HEAD.