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Fri, 13 Nov 2026 00:29:42 -0800 (PST) Date: Fri, 13 Nov 2026 00:29:42 -0800 X-Google-Appengine-App-Id: s~syzkaller X-Google-Appengine-App-Id-Alias: syzkaller Message-ID: <6af6ca76.ff6dfe28.557e.0025.GAE@google.com> Subject: [syzbot] [ext4?] WARNING in start_this_handle From: syzbot To: jack@suse.cz, linux-ext4@vger.kernel.org, linux-kernel@vger.kernel.org, syzkaller-bugs@googlegroups.com, tytso@mit.edu Content-Type: text/plain; charset="UTF-8" Hello, syzbot found the following issue on: HEAD commit: 7e1392a42ea2 Merge tag 'net-7.4-rc3' of git://git.kernel.o.. git tree: upstream console output: https://syzkaller.appspot.com/x/log.txt?x=163a62c3580000 kernel config: https://syzkaller.appspot.com/x/.config?x=3cc6a7ee2d24d208 dashboard link: https://syzkaller.appspot.com/bug?extid=25d45c0bd716f2b794a7 compiler: Debian clang version 22.1.8 (1~deb13u4), Debian LLD 22.1.8 syz repro: https://syzkaller.appspot.com/x/repro.syz?x=12b79aad580000 C reproducer: https://syzkaller.appspot.com/x/repro.c?x=16a501ad580000 Downloadable assets: disk image (non-bootable): https://storage.googleapis.com/syzbot-assets/d900f083ada3/non_bootable_disk-7e1392a4.raw.xz vmlinux: https://storage.googleapis.com/syzbot-assets/77888612dedb/vmlinux-7e1392a4.xz kernel image: https://storage.googleapis.com/syzbot-assets/99bd86cd6b67/bzImage-7e1392a4.xz mounted in repro: https://storage.googleapis.com/syzbot-assets/196af8ecb072/mount_0.gz fsck result: OK (log: https://syzkaller.appspot.com/x/fsck.log?x=11e37fe1580000) AI-generated root cause summary: When setting a large extended attribute on an ext4 filesystem formatted with a 1KB block size, the ea_inode feature, and a minimum-sized JBD2 journal (1024 blocks), __ext4_xattr_set_credits() calculates a worst-case credit requirement of up to 341 blocks (accounting for creating a new ea_inode, dereferencing an old ea_inode, and metadata updates). However, for a 1024-block journal, jbd2_max_user_trans_buffers() limits transaction payload credits to 334 blocks. Because ext4 does not validate at mount time that the journal is large enough to support the ea_inode feature nor limits requested credits in ext4_xattr_set(), jbd2__journal_start() requests more credits than the journal allows, triggering a WARN_ON(1) in start_this_handle() and returning -ENOSPC. full analysis: https://syzkaller.appspot.com/x/ai_root_cause?x=25d45c0bd716f2b794a7 IMPORTANT: if you fix the issue, please add the following tag to the commit: Reported-by: syzbot+25d45c0bd716f2b794a7@syzkaller.appspotmail.com ext4 filesystem being mounted at /0/file0 supports timestamps until 2038-01-19 (0x7fffffff) JBD2: syz.0.17 wants too many credits credits:341 rsv_credits:0 max:334 ------------[ cut here ]------------ 1 WARNING: fs/jbd2/transaction.c:334 at start_this_handle+0x1e3f/0x21f0 fs/jbd2/transaction.c:334, CPU#0: syz.0.17/5590 Modules linked in: CPU: 0 UID: 0 PID: 5590 Comm: syz.0.17 Not tainted syzkaller #0 PREEMPT(full) Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2 04/01/2014 RIP: 0010:start_this_handle+0x1e3f/0x21f0 fs/jbd2/transaction.c:334 Code: 8b 35 ed a2 2f 12 48 81 c6 20 09 00 00 48 c7 c7 c0 8c 48 8c 48 8b 94 24 90 00 00 00 48 8b 4c 24 38 41 89 d8 e8 62 c5 74 fe 90 <0f> 0b 90 b8 e4 ff ff ff e9 35 fe ff ff e8 8f 34 16 ff eb 05 e8 88 RSP: 0018:ffffc90001dc7500 EFLAGS: 00010246 RAX: 0000000000000047 RBX: 000000000000014e RCX: 0d7a67c029606f00 RDX: 0000000000000000 RSI: 8000000000000000 RDI: 0000000000000000 RBP: ffffc90001dc77e0 R08: ffffc90001dc7287 R09: 1ffff920003b8e50 R10: dffffc0000000000 R11: fffff520003b8e51 R12: 0000000000000000 R13: 0000000000000c40 R14: dffffc0000000000 R15: 0000000000000155 FS: 000055557077c500(0000) GS:ffff88808a9f6000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 0000200000013000 CR3: 0000000041ad4000 CR4: 0000000000352ef0 Call Trace: jbd2__journal_start+0x2c0/0x5d0 fs/jbd2/transaction.c:502 __ext4_journal_start_sb+0x205/0x780 fs/ext4/ext4_jbd2.c:126 __ext4_journal_start fs/ext4/ext4_jbd2.h:238 [inline] ext4_xattr_set+0x221/0x340 fs/ext4/xattr.c:2557 __vfs_setxattr+0x442/0x480 fs/xattr.c:223 __vfs_setxattr_noperm+0x12a/0x660 fs/xattr.c:257 vfs_setxattr+0x151/0x370 fs/xattr.c:344 do_setxattr fs/xattr.c:662 [inline] filename_setxattr+0x296/0x630 fs/xattr.c:690 path_setxattrat+0x408/0x450 fs/xattr.c:734 __do_sys_setxattr fs/xattr.c:768 [inline] __se_sys_setxattr fs/xattr.c:764 [inline] __x64_sys_setxattr+0xbc/0xe0 fs/xattr.c:764 do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline] do_syscall_64+0x16a/0x530 arch/x86/entry/syscall_64.c:89 entry_SYSCALL_64_after_hwframe+0x77/0x7f RIP: 0033:0x7f918c1a94d9 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:00007fff574286f8 EFLAGS: 00000246 ORIG_RAX: 00000000000000bc RAX: ffffffffffffffda RBX: 00007f918c425fa0 RCX: 00007f918c1a94d9 RDX: 0000200000003d00 RSI: 0000200000003cc0 RDI: 0000200000003c80 RBP: 00007f918c23804e R08: 0000000000000000 R09: 0000000000000000 R10: 000000000000ff10 R11: 0000000000000246 R12: 0000000000000000 R13: 00007f918c425fac R14: 00007f918c425fa0 R15: 00007f918c425fa0 --- This report is generated by a bot. It may contain errors. See https://goo.gl/tpsmEJ for more information about syzbot. syzbot engineers can be reached at syzkaller@googlegroups.com. syzbot will keep track of this issue. See: https://goo.gl/tpsmEJ#status for how to communicate with syzbot. If the report is already addressed, let syzbot know by replying with: #syz fix: exact-commit-title If you want to overwrite report's subsystems, reply with: #syz set subsystems: new-subsystem (See the list of subsystem names on the web dashboard) If the report is a duplicate of another one, reply with: #syz dup: exact-subject-of-another-report If you want to undo deduplication, reply with: #syz undup