Message-ID: <6989419b.050a0220.3b3015.0065.GAE@google.com>
Date: Sun, 08 Feb 2026 18:08:27 -0800
From: syzbot <syzbot+ccf1421545dbe5caa20c@...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: [syzbot] [ext4?] kernel BUG in ext4_es_cache_extent (4)

Hello,

syzbot found the following issue on:

HEAD commit:    0f8a890c4524 Add linux-next specific files for 20260204
git tree:       linux-next
console output: https://syzkaller.appspot.com/x/log.txt?x=12d547fa580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=c09aefae2687abea
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
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=16420a52580000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/3c923d50ef46/disk-0f8a890c.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/3a560206fcf3/vmlinux-0f8a890c.xz
kernel image: https://storage.googleapis.com/syzbot-assets/e0826a2ee028/bzImage-0f8a890c.xz
mounted in repro: https://storage.googleapis.com/syzbot-assets/4532e6e390d7/mount_0.gz
  fsck result: failed (log: https://syzkaller.appspot.com/x/fsck.log?x=1533aa5a580000)

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+ccf1421545dbe5caa20c@...kaller.appspotmail.com

EXT4-fs warning (device loop0): ext4_es_cache_extent:1082: inode #18: comm syz.0.37: ES cache extent failed: add [22,10,230,0x1] conflict with existing [17,15,145,0x2]
EXT4-fs warning (device loop0): ext4_es_cache_extent:1082: inode #18: comm syz.0.37: ES cache extent failed: add [32,1,353,0x1] conflict with existing [32,1,161,0x2]
EXT4-fs warning (device loop0): ext4_es_cache_extent:1082: inode #18: comm syz.0.37: ES cache extent failed: add [33,15,353,0x1] conflict with existing [33,15,161,0x2]
------------[ cut here ]------------
kernel BUG at fs/ext4/extents_status.c:1044!
Oops: invalid opcode: 0000 [#1] SMP KASAN PTI
CPU: 0 UID: 0 PID: 6168 Comm: syz.0.37 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+0x875/0x9e0 fs/ext4/extents_status.c:1044
Code: e1 07 80 c1 03 38 c1 0f 8c 5c fe ff ff 48 8b 7c 24 18 e8 7e 15 ae ff e9 4d fe ff ff e8 a4 32 44 ff 90 0f 0b e8 9c 32 44 ff 90 <0f> 0b 65 8b 1d f6 c4 99 10 bf 07 00 00 00 89 de e8 c6 36 44 ff 83
RSP: 0018:ffffc90003dedb80 EFLAGS: 00010293
RAX: ffffffff82816b34 RBX: 0000000000000023 RCX: ffff8880271c9e40
RDX: 0000000000000000 RSI: 0000000000000030 RDI: 0000000000000023
RBP: ffffc90003dedcc8 R08: ffffc90003dedc37 R09: 0000000000000000
R10: ffffc90003dedc20 R11: fffff520007bdb87 R12: ffffc90003dedc20
R13: 0000000000000030 R14: 000000000000000f R15: dffffc0000000000
FS:  000055556ddfe500(0000) GS:ffff88812546d000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f56b9c15000 CR3: 0000000079388000 CR4: 00000000003526f0
Call Trace:
 <TASK>
 ext4_cache_extents fs/ext4/extents.c:539 [inline]
 __read_extent_tree_block+0x4b4/0x890 fs/ext4/extents.c:586
 ext4_find_extent+0x76b/0xcc0 fs/ext4/extents.c:941
 ext4_ext_map_blocks+0x283/0x58b0 fs/ext4/extents.c:4263
 ext4_map_create_blocks+0x11d/0x540 fs/ext4/inode.c:616
 ext4_map_blocks+0x7cd/0x11d0 fs/ext4/inode.c:809
 _ext4_get_block+0x1e3/0x470 fs/ext4/inode.c:909
 ext4_get_block_unwritten+0x2e/0x100 fs/ext4/inode.c:942
 ext4_block_write_begin+0xb14/0x1950 fs/ext4/inode.c:1196
 ext4_write_begin+0xb40/0x18c0 fs/ext4/ext4_jbd2.h:-1
 ext4_da_write_begin+0x355/0xd80 fs/ext4/inode.c:3123
 generic_perform_write+0x2e2/0x8f0 mm/filemap.c:4314
 ext4_buffered_write_iter+0xce/0x3a0 fs/ext4/file.c:300
 ext4_file_write_iter+0x298/0x1bf0 fs/ext4/file.c:-1
 __kernel_write_iter+0x41e/0x880 fs/read_write.c:621
 dump_emit_page fs/coredump.c:1299 [inline]
 dump_user_range+0xb89/0x12d0 fs/coredump.c:1373
 elf_core_dump+0x34c2/0x3ad0 fs/binfmt_elf.c:2111
 coredump_write+0x1219/0x1950 fs/coredump.c:1050
 do_coredump fs/coredump.c:1127 [inline]
 vfs_coredump+0x36a9/0x4280 fs/coredump.c:1201
 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:64 [inline]
 exit_to_user_mode_loop kernel/entry/common.c:98 [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:219
 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: 00007efd00215fa0 RCX: 00007efcfff9aeb9
RDX: 0000000000000000 RSI: 0000200000000540 RDI: 0000000000000000
RBP: 00007efd00008c1f R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007efd00215fac R14: 00007efd00215fa0 R15: 00007efd00215fa0
 </TASK>
Modules linked in:
---[ end trace 0000000000000000 ]---
RIP: 0010:ext4_es_cache_extent+0x875/0x9e0 fs/ext4/extents_status.c:1044
Code: e1 07 80 c1 03 38 c1 0f 8c 5c fe ff ff 48 8b 7c 24 18 e8 7e 15 ae ff e9 4d fe ff ff e8 a4 32 44 ff 90 0f 0b e8 9c 32 44 ff 90 <0f> 0b 65 8b 1d f6 c4 99 10 bf 07 00 00 00 89 de e8 c6 36 44 ff 83
RSP: 0018:ffffc90003dedb80 EFLAGS: 00010293
RAX: ffffffff82816b34 RBX: 0000000000000023 RCX: ffff8880271c9e40
RDX: 0000000000000000 RSI: 0000000000000030 RDI: 0000000000000023
RBP: ffffc90003dedcc8 R08: ffffc90003dedc37 R09: 0000000000000000
R10: ffffc90003dedc20 R11: fffff520007bdb87 R12: ffffc90003dedc20
R13: 0000000000000030 R14: 000000000000000f R15: dffffc0000000000
FS:  000055556ddfe500(0000) GS:ffff88812556d000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 000000c00426e000 CR3: 0000000079388000 CR4: 00000000003526f0


---
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