linux-kernel - Re: [syzbot] [ext4?] kernel BUG in ext4_ext_insert

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives
Hash Suite: Windows password security audit tool. GUI, reports in PDF.
[<prev] [next>] [<thread-prev] [day] [month] [year] [list]
Message-ID: <68582a01.050a0220.bba34.0008.GAE@google.com>
Date: Sun, 22 Jun 2025 09:06:25 -0700
From: syzbot <syzbot+ad86dcdffd6785f56e03@...kaller.appspotmail.com>
To: adilger.kernel@...ger.ca, linux-ext4@...r.kernel.org, 
	linux-kernel@...r.kernel.org, syzkaller-bugs@...glegroups.com, tytso@....edu
Subject: Re: [syzbot] [ext4?] kernel BUG in ext4_ext_insert_extent (2)

syzbot has found a reproducer for the following issue on:

HEAD commit:    739a6c93cc75 Merge tag 'nfsd-6.16-1' of git://git.kernel.o..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=15a19b0c580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=d11f52d3049c3790
dashboard link: https://syzkaller.appspot.com/bug?extid=ad86dcdffd6785f56e03
compiler:       Debian clang version 20.1.6 (++20250514063057+1e4d39e07757-1~exp1~20250514183223.118), Debian LLD 20.1.6
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=14af2182580000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/f5a65b9fc0ed/disk-739a6c93.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/3f1b70f2f048/vmlinux-739a6c93.xz
kernel image: https://storage.googleapis.com/syzbot-assets/a8ab27807c85/bzImage-739a6c93.xz
mounted in repro: https://storage.googleapis.com/syzbot-assets/376364fe7b8f/mount_2.gz
  fsck result: failed (log: https://syzkaller.appspot.com/x/fsck.log?x=10af2182580000)

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+ad86dcdffd6785f56e03@...kaller.appspotmail.com

------------[ cut here ]------------
kernel BUG at fs/ext4/extents.c:2153!
Oops: invalid opcode: 0000 [#1] SMP KASAN NOPTI
CPU: 1 UID: 0 PID: 6732 Comm: syz.4.53 Not tainted 6.16.0-rc2-syzkaller-00318-g739a6c93cc75 #0 PREEMPT(full) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/07/2025
RIP: 0010:ext4_ext_insert_extent+0x4ab7/0x4af0 fs/ext4/extents.c:2153
Code: 89 d9 80 e1 07 fe c1 38 c1 0f 8c a6 e7 ff ff 48 89 df e8 2c 8b b6 ff e9 99 e7 ff ff e8 62 0d 53 ff 90 0f 0b e8 5a 0d 53 ff 90 <0f> 0b e8 52 0d 53 ff 90 0f 0b 89 d9 80 e1 07 80 c1 03 38 c1 0f 8c
RSP: 0018:ffffc9000455ec60 EFLAGS: 00010293
RAX: ffffffff826d4f26 RBX: 0000000000000023 RCX: ffff888026e93c00
RDX: 0000000000000000 RSI: 0000000000000023 RDI: 0000000000000023
RBP: ffffc9000455ee10 R08: ffff8880609943a7 R09: 1ffff1100c132874
R10: dffffc0000000000 R11: ffffed100c132875 R12: 0000000000000023
R13: dffffc0000000000 R14: ffff88806bfde448 R15: ffff888027bf3d00
FS:  00007fe4a5ed66c0(0000) GS:ffff888125d51000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000200000003000 CR3: 0000000070c0d000 CR4: 0000000000350ef0
Call Trace:
 <TASK>
 ext4_ext_map_blocks+0x1792/0x6ac0 fs/ext4/extents.c:4404
 ext4_map_create_blocks fs/ext4/inode.c:609 [inline]
 ext4_map_blocks+0x931/0x18d0 fs/ext4/inode.c:813
 _ext4_get_block+0x200/0x4c0 fs/ext4/inode.c:892
 ext4_get_block_unwritten+0x2e/0x100 fs/ext4/inode.c:925
 ext4_block_write_begin+0x6f8/0x14b0 fs/ext4/inode.c:1178
 ext4_write_begin+0xa4f/0x1680 fs/ext4/ext4_jbd2.h:-1
 ext4_da_write_begin+0x449/0xd20 fs/ext4/inode.c:3057
 generic_perform_write+0x2c7/0x910 mm/filemap.c:4112
 ext4_buffered_write_iter+0xce/0x3a0 fs/ext4/file.c:299
 ext4_file_write_iter+0x298/0x1bc0 fs/ext4/file.c:-1
 do_iter_readv_writev+0x56e/0x7f0 fs/read_write.c:-1
 vfs_writev+0x31a/0x960 fs/read_write.c:1057
 do_pwritev fs/read_write.c:1153 [inline]
 __do_sys_pwritev2 fs/read_write.c:1211 [inline]
 __se_sys_pwritev2+0x179/0x290 fs/read_write.c:1202
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xfa/0x3b0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7fe4a4f8e929
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:00007fe4a5ed6038 EFLAGS: 00000246 ORIG_RAX: 0000000000000148
RAX: ffffffffffffffda RBX: 00007fe4a51b5fa0 RCX: 00007fe4a4f8e929
RDX: 0000000000000001 RSI: 0000200000000100 RDI: 0000000000000004
RBP: 00007fe4a5010b39 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000005412 R11: 0000000000000246 R12: 0000000000000000
R13: 0000000000000000 R14: 00007fe4a51b5fa0 R15: 00007fffc4eaed48
 </TASK>
Modules linked in:
---[ end trace 0000000000000000 ]---
RIP: 0010:ext4_ext_insert_extent+0x4ab7/0x4af0 fs/ext4/extents.c:2153
Code: 89 d9 80 e1 07 fe c1 38 c1 0f 8c a6 e7 ff ff 48 89 df e8 2c 8b b6 ff e9 99 e7 ff ff e8 62 0d 53 ff 90 0f 0b e8 5a 0d 53 ff 90 <0f> 0b e8 52 0d 53 ff 90 0f 0b 89 d9 80 e1 07 80 c1 03 38 c1 0f 8c
RSP: 0018:ffffc9000455ec60 EFLAGS: 00010293
RAX: ffffffff826d4f26 RBX: 0000000000000023 RCX: ffff888026e93c00
RDX: 0000000000000000 RSI: 0000000000000023 RDI: 0000000000000023
RBP: ffffc9000455ee10 R08: ffff8880609943a7 R09: 1ffff1100c132874
R10: dffffc0000000000 R11: ffffed100c132875 R12: 0000000000000023
R13: dffffc0000000000 R14: ffff88806bfde448 R15: ffff888027bf3d00
FS:  00007fe4a5ed66c0(0000) GS:ffff888125d51000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00005610a8772950 CR3: 0000000070c0d000 CR4: 0000000000350ef0


---
If you want syzbot to run the reproducer, reply with:
#syz test: git://repo/address.git branch-or-commit-hash
If you attach or paste a git patch, syzbot will apply it before testing.