Re: [syzbot] [ext4?] kernel BUG in ext4_es_cache_extent (4)

[syzbot <syzbot+ccf1421545dbe5caa20c@syzkaller.appspotmail.com>]

Hello,

syzbot has tested the proposed patch but the reproducer is still triggering an issue:
kernel BUG in ext4_es_cache_extent

EXT4-fs warning (device loop7): ext4_es_cache_extent:1081: inode #18: comm syz.7.209: ES cache extent failed: add [33,3,18446744073709551615,0x8] conflict with existing [33,15,257,0x2]
EXT4-fs warning (device loop7): ext4_es_cache_extent:1081: inode #18: comm syz.7.209: ES cache extent failed: add [36,12,292,0x1] conflict with existing [33,15,257,0x2]
------------[ cut here ]------------
kernel BUG at fs/ext4/extents_status.c:1043!
Oops: invalid opcode: 0000 [#1] SMP KASAN PTI
CPU: 1 UID: 0 PID: 9040 Comm: syz.7.209 Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/24/2026
RIP: 0010:ext4_es_cache_extent+0x86e/0x990 fs/ext4/extents_status.c:1043
Code: e1 07 80 c1 03 38 c1 0f 8c 5d fe ff ff 48 8b 7c 24 20 e8 25 4d af ff e9 4e fe ff ff e8 1b 12 47 ff 90 0f 0b e8 13 12 47 ff 90 <0f> 0b 65 8b 1d 9d 73 6e 10 bf 07 00 00 00 89 de e8 3d 16 47 ff 83
RSP: 0018:ffffc900054fdba0 EFLAGS: 00010293
RAX: ffffffff827d2c8d RBX: 0000000000000023 RCX: ffff88801dfe8000
RDX: 0000000000000000 RSI: 0000000000000030 RDI: 0000000000000023
RBP: ffffc900054fdce8 R08: ffffc900054fdc57 R09: 0000000000000000
R10: ffffc900054fdc40 R11: fffff52000a9fb8b R12: 0000000000000030
R13: dffffc0000000000 R14: 000000000000000f R15: ffff88807d100638
FS:  00007efd221aa6c0(0000) GS:ffff888125866000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007fbc5c5e8600 CR3: 000000007569c000 CR4: 00000000003526f0
Call Trace:
 <TASK>
 ext4_cache_extents fs/ext4/extents.c:544 [inline]
 __read_extent_tree_block+0x4b4/0x840 fs/ext4/extents.c:591
 ext4_find_extent+0x76b/0xcc0 fs/ext4/extents.c:944
 ext4_ext_map_blocks+0x29d/0x6cd0 fs/ext4/extents.c:4239
 ext4_map_create_blocks fs/ext4/inode.c:613 [inline]
 ext4_map_blocks+0x8da/0x1830 fs/ext4/inode.c:816
 _ext4_get_block+0x1e3/0x470 fs/ext4/inode.c:916
 ext4_get_block_unwritten+0x2e/0x100 fs/ext4/inode.c:949
 ext4_block_write_begin+0xb14/0x1950 fs/ext4/inode.c:1203
 ext4_write_begin+0xb40/0x1870 fs/ext4/ext4_jbd2.h:-1
 ext4_da_write_begin+0x355/0xd30 fs/ext4/inode.c:3130
 generic_perform_write+0x2e2/0x8f0 mm/filemap.c:4314
 ext4_buffered_write_iter+0xce/0x3a0 fs/ext4/file.c:299
 ext4_file_write_iter+0x298/0x1c10 fs/ext4/file.c:-1
 __kernel_write_iter+0x41e/0x880 fs/read_write.c:619
 dump_emit_page fs/coredump.c:1298 [inline]
 dump_user_range+0xb89/0x12d0 fs/coredump.c:1372
 elf_core_dump+0x34c2/0x3ad0 fs/binfmt_elf.c:2111
 coredump_write+0x1219/0x1950 fs/coredump.c:1049
 do_coredump fs/coredump.c:1126 [inline]
 vfs_coredump+0x369e/0x4270 fs/coredump.c:1200
 get_signal+0x1107/0x1330 kernel/signal.c:3019
 arch_do_signal_or_restart+0xbc/0x830 arch/x86/kernel/signal.c:337
 __exit_to_user_mode_loop kernel/entry/common.c:41 [inline]
 exit_to_user_mode_loop kernel/entry/common.c:75 [inline]
 __exit_to_user_mode_prepare include/linux/irq-entry-common.h:226 [inline]
 irqentry_exit_to_user_mode_prepare include/linux/irq-entry-common.h:270 [inline]
 irqentry_exit_to_user_mode include/linux/irq-entry-common.h:339 [inline]
 irqentry_exit+0x176/0x620 kernel/entry/common.c:196
 asm_exc_page_fault+0x26/0x30 arch/x86/include/asm/idtentry.h:618
RIP: 0033:0x0
Code: Unable to access opcode bytes at 0xffffffffffffffd6.
RSP: 002b:0000200000000548 EFLAGS: 00010217
RAX: 0000000000000000 RBX: 00007efd21615fa0 RCX: 00007efd2139aeb9
RDX: 0000000000000000 RSI: 0000200000000540 RDI: 0000000000000000
RBP: 00007efd21408c1f R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007efd21616038 R14: 00007efd21615fa0 R15: 00007ffc2b2553f8
 </TASK>
Modules linked in:
---[ end trace 0000000000000000 ]---
RIP: 0010:ext4_es_cache_extent+0x86e/0x990 fs/ext4/extents_status.c:1043
Code: e1 07 80 c1 03 38 c1 0f 8c 5d fe ff ff 48 8b 7c 24 20 e8 25 4d af ff e9 4e fe ff ff e8 1b 12 47 ff 90 0f 0b e8 13 12 47 ff 90 <0f> 0b 65 8b 1d 9d 73 6e 10 bf 07 00 00 00 89 de e8 3d 16 47 ff 83
RSP: 0018:ffffc900054fdba0 EFLAGS: 00010293
RAX: ffffffff827d2c8d RBX: 0000000000000023 RCX: ffff88801dfe8000
RDX: 0000000000000000 RSI: 0000000000000030 RDI: 0000000000000023
RBP: ffffc900054fdce8 R08: ffffc900054fdc57 R09: 0000000000000000
R10: ffffc900054fdc40 R11: fffff52000a9fb8b R12: 0000000000000030
R13: dffffc0000000000 R14: 000000000000000f R15: ffff88807d100638
FS:  00007efd221aa6c0(0000) GS:ffff888125766000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f82eec0f000 CR3: 000000007569c000 CR4: 00000000003526f0


Tested on:

commit:         26f260ce ext4: remove unnecessary zero-initialization ..
git tree:       https://git.kernel.org/pub/scm/linux/kernel/git/tytso/ext4.git
console output: https://syzkaller.appspot.com/x/log.txt?x=12dcd78a580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=a535ad5429f72a2
dashboard link: https://syzkaller.appspot.com/bug?extid=ccf1421545dbe5caa20c
compiler:       Debian clang version 21.1.8 (++20251221033036+2078da43e25a-1~exp1~20251221153213.50), Debian LLD 21.1.8

Note: no patches were applied.