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kernel BUG in ext4_split_extent_at

Status: upstream: reported C repro on 2025/05/29 02:28
Bug presence: origin:lts
Labels: missing-backport
[Documentation on labels]
Reported-by: syzbot+d7a12cd97b9a104c4ab2@syzkaller.appspotmail.com
First crash: 730d, last: 10d
Cause bisection: failed (error log, bisect log)
  
Fix bisection: failed (error log, bisect log)
  
▶ ▼ Bug presence (2)
Date Name Commit Repro Result
2025/05/29 lts (merge base) 98f47d0e9b8c C [report] kernel BUG in ext4_split_extent_at
2025/05/29 upstream (ToT) 90b83efa6701 C Didn't crash
▶ ▼ Similar bugs (4)
Kernel Title Repro Cause bisect Fix bisect Count Last Reported Patched Status
upstream kernel BUG in ext4_split_extent_at ext4 1 1216d 1211d 0/28 auto-closed as invalid on 2022/06/08 01:32
android-5-10 kernel BUG in ext4_split_extent_at C error error 9 9d17h 730d 0/2 upstream: reported C repro on 2023/06/09 00:07
upstream kernel BUG in ext4_split_extent_at (2) ext4 C error done 3 531d 726d 25/28 fixed on 2024/01/30 15:47
android-6-1 kernel BUG in ext4_split_extent_at missing-backport origin:upstream C error error 1 268d 730d 0/2 auto-obsoleted due to no activity on 2024/12/21 09:12
▶ ▼ Last patch testing requests (3)
Created Duration User Patch Repo Result
2025/05/18 19:47 9m retest repro android13-5.15-lts report log
2025/03/05 18:09 7m retest repro android13-5.15-lts report log
2024/12/25 17:19 8m retest repro android13-5.15-lts report log
▶ ▼ Fix bisection attempts (8)
Created Duration User Patch Repo Result
2024/10/15 03:31 0m bisect fix android13-5.15-lts error job log
2024/06/14 05:25 1h06m bisect fix android13-5.15-lts OK (0) job log log
2024/03/20 16:02 1h09m bisect fix android13-5.15-lts OK (0) job log log
2024/02/11 17:35 1h00m bisect fix android13-5.15-lts OK (0) job log log
2023/12/29 21:10 1h08m bisect fix android13-5.15-lts OK (0) job log log
2023/11/27 15:29 1h23m bisect fix android13-5.15-lts OK (0) job log log
2023/10/28 10:56 1h00m bisect fix android13-5.15-lts OK (0) job log log
2023/07/16 20:39 1h24m bisect fix android13-5.15-lts OK (0) job log log

Sample crash report:
------------[ cut here ]------------
kernel BUG at fs/ext4/extents.c:3185!
invalid opcode: 0000 [#1] PREEMPT SMP KASAN
CPU: 0 PID: 320 Comm: syz-executor409 Not tainted 5.15.184-syzkaller-00129-g4032a894ccb2 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/07/2025
RIP: 0010:ext4_split_extent_at+0xe77/0xe90 fs/ext4/extents.c:3185
Code: 6f fb ff ff 48 89 df 49 89 d7 e8 b4 89 d3 ff 4c 89 fa e9 5c fb ff ff e8 57 18 95 ff 0f 0b e8 50 18 95 ff 0f 0b e8 49 18 95 ff <0f> 0b e8 42 18 95 ff 0f 0b e8 3b 18 95 ff 0f 0b e8 34 18 95 ff 0f
RSP: 0018:ffffc90000c664e0 EFLAGS: 00010293
RAX: ffffffff81d38c97 RBX: 1ffff110228a7402 RCX: ffff88810d892780
RDX: 0000000000000000 RSI: 000000000000003d RDI: 0000000000000020
RBP: ffffc90000c66650 R08: 0000000000000010 R09: 000000000000003b
R10: ffffed1021df1c4a R11: 1ffff11021df1c48 R12: dffffc0000000000
R13: 0000000000000020 R14: 000000000000000b R15: 0000000000000010
FS:  00007f44fce546c0(0000) GS:ffff8881f7000000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007ffe1d9f5ee8 CR3: 00000001231d0000 CR4: 00000000003506b0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 <TASK>
 ext4_split_extent+0x386/0x4e0 fs/ext4/extents.c:3384
 ext4_split_convert_extents fs/ext4/extents.c:3714 [inline]
 ext4_ext_handle_unwritten_extents fs/ext4/extents.c:3875 [inline]
 ext4_ext_map_blocks+0x1b6c/0x6270 fs/ext4/extents.c:4230
 ext4_map_blocks+0x97b/0x1b20 fs/ext4/inode.c:674
 _ext4_get_block+0x1da/0x4e0 fs/ext4/inode.c:817
 ext4_get_block_unwritten+0x2a/0x40 fs/ext4/inode.c:848
 ext4_block_write_begin+0x556/0x1150 fs/ext4/inode.c:1102
 ext4_write_begin+0x638/0x1220 fs/ext4/ext4_jbd2.h:-1
 ext4_da_write_begin+0x2fa/0xb60 fs/ext4/inode.c:2988
 generic_perform_write+0x2ad/0x670 mm/filemap.c:3857
 ext4_buffered_write_iter+0x4ed/0x670 fs/ext4/file.c:270
 ext4_file_write_iter+0x18c/0x14c0 fs/ext4/file.c:664
 do_iter_readv_writev+0x491/0x600 fs/read_write.c:-1
 do_iter_write+0x1fa/0x7b0 fs/read_write.c:855
 vfs_iter_write+0x7d/0xa0 fs/read_write.c:896
 iter_file_splice_write+0x650/0xc30 fs/splice.c:689
 do_splice_from fs/splice.c:767 [inline]
 direct_splice_actor+0xe9/0x120 fs/splice.c:936
 splice_direct_to_actor+0x4cd/0xb30 fs/splice.c:891
 do_splice_direct+0x1b3/0x2c0 fs/splice.c:979
 do_sendfile+0x5c6/0xeb0 fs/read_write.c:1249
 __do_sys_sendfile64 fs/read_write.c:1317 [inline]
 __se_sys_sendfile64 fs/read_write.c:1303 [inline]
 __x64_sys_sendfile64+0x18f/0x1f0 fs/read_write.c:1303
 x64_sys_call+0x88d/0x9a0 arch/x86/include/generated/asm/syscalls_64.h:41
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x66/0xd0
RIP: 0033:0x7f44fcea6089
Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 c1 1f 00 00 90 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 b0 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f44fce54218 EFLAGS: 00000246 ORIG_RAX: 0000000000000028
RAX: ffffffffffffffda RBX: 00007f44fcf2d4e8 RCX: 00007f44fcea6089
RDX: 0000000000000000 RSI: 0000000000000008 RDI: 0000000000000005
RBP: 00007f44fcf2d4e0 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000100001 R11: 0000000000000246 R12: 00007f44fcef2df4
R13: 0000200000000080 R14: 0000200000000400 R15: 0000200000000000
 </TASK>
Modules linked in:
---[ end trace 958a5b50ea8091c1 ]---
RIP: 0010:ext4_split_extent_at+0xe77/0xe90 fs/ext4/extents.c:3185
Code: 6f fb ff ff 48 89 df 49 89 d7 e8 b4 89 d3 ff 4c 89 fa e9 5c fb ff ff e8 57 18 95 ff 0f 0b e8 50 18 95 ff 0f 0b e8 49 18 95 ff <0f> 0b e8 42 18 95 ff 0f 0b e8 3b 18 95 ff 0f 0b e8 34 18 95 ff 0f
RSP: 0018:ffffc90000c664e0 EFLAGS: 00010293
RAX: ffffffff81d38c97 RBX: 1ffff110228a7402 RCX: ffff88810d892780
RDX: 0000000000000000 RSI: 000000000000003d RDI: 0000000000000020
RBP: ffffc90000c66650 R08: 0000000000000010 R09: 000000000000003b
R10: ffffed1021df1c4a R11: 1ffff11021df1c48 R12: dffffc0000000000
R13: 0000000000000020 R14: 000000000000000b R15: 0000000000000010
FS:  00007f44fce546c0(0000) GS:ffff8881f7100000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007fa394a88000 CR3: 00000001231d0000 CR4: 00000000003506a0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400

Crashes (2):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2025/05/29 02:27 android13-5.15-lts 4032a894ccb2 3d2f584d .config console log report syz / log C [disk image] [vmlinux] [kernel image] [mounted in repro (corrupt fs)] ci2-android-5-15 kernel BUG in ext4_split_extent_at
2023/06/09 01:16 android13-5.15-lts 19c0ed55a470 058b3a5a .config console log report syz [disk image] [vmlinux] [kernel image] [mounted in repro] ci2-android-5-15 kernel BUG in ext4_split_extent_at
* Struck through repros no longer work on HEAD.