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

[syzbot]

syzbot has found a reproducer for the following issue on:

HEAD commit:    af4e9ef3d784 uaccess: Fix scoped_user_read_access() for 'p..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=13811b5a580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=779072223d02a312
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=1620e552580000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=13810a02580000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/f6b75c8f432f/disk-af4e9ef3.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/4513ad566789/vmlinux-af4e9ef3.xz
kernel image: https://storage.googleapis.com/syzbot-assets/f7eea878db42/bzImage-af4e9ef3.xz
mounted in repro: https://storage.googleapis.com/syzbot-assets/8d81a7f0b7b8/mount_0.gz
  fsck result: failed (log: https://syzkaller.appspot.com/x/fsck.log?x=1351b006580000)

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

EXT4-fs warning (device loop0): ext4_es_cache_extent:1082: inode #15: comm syz.0.36: ES cache extent failed: add [0,1,177,0x1] conflict with existing [0,1,113,0x2]
EXT4-fs warning (device loop0): ext4_es_cache_extent:1082: inode #15: comm syz.0.36: ES cache extent failed: add [1,15,177,0x1] conflict with existing [1,35,576460752303423487,0x18]
EXT4-fs warning (device loop0): ext4_es_cache_extent:1082: inode #15: comm syz.0.36: ES cache extent failed: add [16,1,177,0x1] conflict with existing [1,35,576460752303423487,0x18]
EXT4-fs warning (device loop0): ext4_es_cache_extent:1082: inode #15: comm syz.0.36: ES cache extent failed: add [17,10,177,0x1] conflict with existing [1,35,576460752303423487,0x18]
------------[ cut here ]------------
kernel BUG at fs/ext4/extents_status.c:1044!
Oops: invalid opcode: 0000 [#1] SMP KASAN NOPTI
CPU: 0 UID: 0 PID: 6062 Comm: syz.0.36 Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2026
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 fe ac ad ff e9 4d fe ff ff e8 a4 6e 43 ff 90 0f 0b e8 9c 6e 43 ff 90 <0f> 0b 65 8b 1d e6 98 99 10 bf 07 00 00 00 89 de e8 c6 72 43 ff 83
RSP: 0018:ffffc90003456d20 EFLAGS: 00010293
RAX: ffffffff82822744 RBX: 0000000000000018 RCX: ffff88803155bd00
RDX: 0000000000000000 RSI: 000000000000001b RDI: 0000000000000018
RBP: ffffc90003456e68 R08: ffffc90003456dd7 R09: ffffc90003456dc0
R10: dffffc0000000000 R11: fffff5200068adbb R12: ffffc90003456dc0
R13: 000000000000001b R14: 000000000000000f R15: dffffc0000000000
FS:  00007fbdae25d6c0(0000) GS:ffff888125464000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007fbdad3e9e80 CR3: 00000000781f0000 CR4: 0000000000350ef0
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+0x76f/0xcc0 fs/ext4/extents.c:939
 ext4_ext_map_blocks+0x283/0x58b0 fs/ext4/extents.c:4261
 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
 new_sync_write fs/read_write.c:595 [inline]
 vfs_write+0x61d/0xb90 fs/read_write.c:688
 ksys_pwrite64 fs/read_write.c:795 [inline]
 __do_sys_pwrite64 fs/read_write.c:803 [inline]
 __se_sys_pwrite64 fs/read_write.c:800 [inline]
 __x64_sys_pwrite64+0x199/0x230 fs/read_write.c:800
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0x14d/0xf80 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7fbdad39c799
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:00007fbdae25d028 EFLAGS: 00000246 ORIG_RAX: 0000000000000012
RAX: ffffffffffffffda RBX: 00007fbdad615fa0 RCX: 00007fbdad39c799
RDX: 00000000200000c1 RSI: 00002000000000c0 RDI: 0000000000000006
RBP: 00007fbdad432bd9 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000009000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fbdad616038 R14: 00007fbdad615fa0 R15: 00007fff33d9aaf8
 </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 fe ac ad ff e9 4d fe ff ff e8 a4 6e 43 ff 90 0f 0b e8 9c 6e 43 ff 90 <0f> 0b 65 8b 1d e6 98 99 10 bf 07 00 00 00 89 de e8 c6 72 43 ff 83
RSP: 0018:ffffc90003456d20 EFLAGS: 00010293
RAX: ffffffff82822744 RBX: 0000000000000018 RCX: ffff88803155bd00
RDX: 0000000000000000 RSI: 000000000000001b RDI: 0000000000000018
RBP: ffffc90003456e68 R08: ffffc90003456dd7 R09: ffffc90003456dc0
R10: dffffc0000000000 R11: fffff5200068adbb R12: ffffc90003456dc0
R13: 000000000000001b R14: 000000000000000f R15: dffffc0000000000
FS:  00007fbdae25d6c0(0000) GS:ffff888125464000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007fbdad3e9e80 CR3: 00000000781f0000 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.