Re: [syzbot] [ext4?] kernel BUG in ext4_es_cache_extent (3)

[syzbot]

Hello,

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

EXT4-fs (loop0): 1 truncate cleaned up
EXT4-fs (loop0): mounted filesystem 00000000-0000-0000-0000-000000000000 r/w without journal. Quota mode: none.
------------[ cut here ]------------
kernel BUG at fs/ext4/extents_status.c:1012!
Oops: invalid opcode: 0000 [#1] SMP KASAN NOPTI
CPU: 0 UID: 0 PID: 5828 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~bpo12+1 04/01/2014
RIP: 0010:ext4_es_cache_extent+0x698/0x700 fs/ext4/extents_status.c:1012
Code: ff df 80 3c 08 00 74 08 48 89 df e8 c2 a7 b3 ff 48 8b 3b 48 8b 74 24 28 48 8d 54 24 60 e8 00 c3 0d 00 eb 14 e8 89 ab 4e ff 90 <0f> 0b e8 81 ab 4e ff eb 28 e8 7a ab 4e ff 31 f6 65 ff 0d 01 71 50
RSP: 0018:ffffc90002bcf420 EFLAGS: 00010293
RAX: ffffffff82711f17 RBX: 00000000ffffffff RCX: ffff888033530000
RDX: 0000000000000000 RSI: 00000000ffffffff RDI: 00000000000052ce
RBP: ffffc90002bcf528 R08: ffffffff8fc3c837 R09: 1ffffffff1f87906
R10: dffffc0000000000 R11: fffffbfff1f87907 R12: 00000000000052d0
R13: 0000000000000004 R14: 00000000000052ce R15: dffffc0000000000
FS: 00007fa99e5616c0(0000) GS:ffff88808d007000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f2d130e10a0 CR3: 0000000042911000 CR4: 0000000000352ef0
Call Trace:
<TASK>
ext4_cache_extents fs/ext4/extents.c:548 [inline]
ext4_find_extent+0x482/0xcc0 fs/ext4/extents.c:932
ext4_get_verity_descriptor_location fs/ext4/verity.c:292 [inline]
ext4_get_verity_descriptor+0x102/0x590 fs/ext4/verity.c:346
fsverity_get_descriptor+0x90/0x4b0 fs/verity/open.c:323
ensure_verity_info fs/verity/open.c:363 [inline]
__fsverity_file_open+0xd7/0x1f0 fs/verity/open.c:384
fsverity_file_open include/linux/fsverity.h:300 [inline]
ext4_file_open+0x32d/0xa40 fs/ext4/file.c:909
do_dentry_open+0x950/0x13f0 fs/open.c:965
vfs_open+0x3b/0x340 fs/open.c:1095
do_open fs/namei.c:3887 [inline]
path_openat+0x2ee5/0x3830 fs/namei.c:4046
do_filp_open+0x1fa/0x410 fs/namei.c:4073
do_sys_openat2+0x121/0x1c0 fs/open.c:1435
do_sys_open fs/open.c:1450 [inline]
__do_sys_openat fs/open.c:1466 [inline]
__se_sys_openat fs/open.c:1461 [inline]
__x64_sys_openat+0x138/0x170 fs/open.c:1461
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: 0033:0x7fa99d78ebe9
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:00007fa99e561038 EFLAGS: 00000246 ORIG_RAX: 0000000000000101
RAX: ffffffffffffffda RBX: 00007fa99d9c5fa0 RCX: 00007fa99d78ebe9
RDX: 0000000000000000 RSI: 0000200000000100 RDI: ffffffffffffff9c
RBP: 00007fa99d811e19 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fa99d9c6038 R14: 00007fa99d9c5fa0 R15: 00007ffcadbf0f68
</TASK>
Modules linked in:
---[ end trace 0000000000000000 ]---
RIP: 0010:ext4_es_cache_extent+0x698/0x700 fs/ext4/extents_status.c:1012
Code: ff df 80 3c 08 00 74 08 48 89 df e8 c2 a7 b3 ff 48 8b 3b 48 8b 74 24 28 48 8d 54 24 60 e8 00 c3 0d 00 eb 14 e8 89 ab 4e ff 90 <0f> 0b e8 81 ab 4e ff eb 28 e8 7a ab 4e ff 31 f6 65 ff 0d 01 71 50
RSP: 0018:ffffc90002bcf420 EFLAGS: 00010293
RAX: ffffffff82711f17 RBX: 00000000ffffffff RCX: ffff888033530000
RDX: 0000000000000000 RSI: 00000000ffffffff RDI: 00000000000052ce
RBP: ffffc90002bcf528 R08: ffffffff8fc3c837 R09: 1ffffffff1f87906
R10: dffffc0000000000 R11: fffffbfff1f87907 R12: 00000000000052d0
R13: 0000000000000004 R14: 00000000000052ce R15: dffffc0000000000
FS: 00007fa99e5616c0(0000) GS:ffff88808d007000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007ffc8e551f4c CR3: 0000000042911000 CR4: 0000000000352ef0


Tested on:

commit: 51a24b7d Merge tag 'trace-tools-v6.17-rc5' of git://gi..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=114f72e2580000
kernel config: https://syzkaller.appspot.com/x/.config?x=bf99f2510ef92ba5
dashboard link: https://syzkaller.appspot.com/bug?extid=038b7bf43423e132b308
compiler: Debian clang version 20.1.8 (++20250708063551+0c9f909b7976-1~exp1~20250708183702.136), Debian LLD 20.1.8
patch: https://syzkaller.appspot.com/x/patch.diff?x=138cfd34580000

[syzbot]

Hello,

syzbot has tested the proposed patch but the reproducer is still triggering an issue:

KASAN: use-after-free Read in ext4_find_extent

EXT4-fs (loop0): mounted filesystem 00000000-0000-0000-0000-000000000000 r/w without journal. Quota mode: none.

EXT4-fs error (device loop0): ext4_cache_extents:545: inode #15: comm syz.0.17: corrupted extent tree: lblk 0 < prev 66
==================================================================
BUG: KASAN: use-after-free in ext4_ext_binsearch fs/ext4/extents.c:848 [inline]
BUG: KASAN: use-after-free in ext4_find_extent+0x85c/0xa20 fs/ext4/extents.c:963
Read of size 4 at addr ffff888041c23e48 by task syz.0.17/5858

CPU: 0 UID: 0 PID: 5858 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~bpo12+1 04/01/2014

Call Trace:
<TASK>
dump_stack_lvl+0x189/0x250 lib/dump_stack.c:120
print_address_description mm/kasan/report.c:378 [inline]
print_report+0xca/0x240 mm/kasan/report.c:482
kasan_report+0x118/0x150 mm/kasan/report.c:595
ext4_ext_binsearch fs/ext4/extents.c:848 [inline]
ext4_find_extent+0x85c/0xa20 fs/ext4/extents.c:963

ext4_get_verity_descriptor_location fs/ext4/verity.c:292 [inline]
ext4_get_verity_descriptor+0x102/0x590 fs/ext4/verity.c:346
fsverity_get_descriptor+0x90/0x4b0 fs/verity/open.c:323
ensure_verity_info fs/verity/open.c:363 [inline]
__fsverity_file_open+0xd7/0x1f0 fs/verity/open.c:384
fsverity_file_open include/linux/fsverity.h:300 [inline]
ext4_file_open+0x32d/0xa40 fs/ext4/file.c:909
do_dentry_open+0x950/0x13f0 fs/open.c:965
vfs_open+0x3b/0x340 fs/open.c:1095
do_open fs/namei.c:3887 [inline]
path_openat+0x2ee5/0x3830 fs/namei.c:4046
do_filp_open+0x1fa/0x410 fs/namei.c:4073
do_sys_openat2+0x121/0x1c0 fs/open.c:1435
do_sys_open fs/open.c:1450 [inline]
__do_sys_openat fs/open.c:1466 [inline]
__se_sys_openat fs/open.c:1461 [inline]
__x64_sys_openat+0x138/0x170 fs/open.c:1461
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: 0033:0x7f6cf3b8ebe9

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:00007f6cf4aaa038 EFLAGS: 00000246 ORIG_RAX: 0000000000000101
RAX: ffffffffffffffda RBX: 00007f6cf3dc5fa0 RCX: 00007f6cf3b8ebe9

RDX: 0000000000000000 RSI: 0000200000000100 RDI: ffffffffffffff9c

RBP: 00007f6cf3c11e19 R08: 0000000000000000 R09: 0000000000000000

R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000

R13: 00007f6cf3dc6038 R14: 00007f6cf3dc5fa0 R15: 00007fff26487178
</TASK>

The buggy address belongs to the physical page:
page: refcount:0 mapcount:0 mapping:0000000000000000 index:0x55b5a552d pfn:0x41c23
flags: 0x4fff00000000000(node=1|zone=1|lastcpupid=0x7ff)
raw: 04fff00000000000 ffffea0001070948 ffffea0001070888 0000000000000000
raw: 000000055b5a552d 0000000000000000 00000000ffffffff 0000000000000000
page dumped because: kasan: bad access detected
page_owner tracks the page as freed
page last allocated via order 0, migratetype Movable, gfp_mask 0x140cca(GFP_HIGHUSER_MOVABLE|__GFP_COMP), pid 5236, tgid 5236 (dhcpcd), ts 65849526604, free_ts 140329459250
set_page_owner include/linux/page_owner.h:32 [inline]
post_alloc_hook+0x240/0x2a0 mm/page_alloc.c:1851
compaction_alloc_noprof mm/compaction.c:1836 [inline]
compaction_alloc+0x3099/0x34a0 mm/compaction.c:1847
migrate_folio_unmap mm/migrate.c:1211 [inline]
migrate_pages_batch+0x7e2/0x35c0 mm/migrate.c:1873
migrate_pages_sync mm/migrate.c:1996 [inline]
migrate_pages+0x1bcc/0x2930 mm/migrate.c:2105
compact_zone+0x23e1/0x4ab0 mm/compaction.c:2647
compact_node+0x1d2/0x280 mm/compaction.c:2916
kcompactd+0xbc8/0x1290 mm/compaction.c:3214
kthread+0x711/0x8a0 kernel/kthread.c:463
ret_from_fork+0x439/0x7d0 arch/x86/kernel/process.c:148
ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
page last free pid 30 tgid 30 stack trace:
reset_page_owner include/linux/page_owner.h:25 [inline]
free_pages_prepare mm/page_alloc.c:1395 [inline]
__free_frozen_pages+0xbc4/0xd30 mm/page_alloc.c:2895
__folio_put+0x21b/0x2c0 mm/swap.c:112
migrate_folio_move mm/migrate.c:1409 [inline]
migrate_folios_move mm/migrate.c:1719 [inline]
migrate_pages_batch+0x227f/0x35c0 mm/migrate.c:1966
migrate_pages_sync mm/migrate.c:1996 [inline]
migrate_pages+0x1bcc/0x2930 mm/migrate.c:2105
compact_zone+0x23e1/0x4ab0 mm/compaction.c:2647
compact_node+0x1d2/0x280 mm/compaction.c:2916
kcompactd+0xbc8/0x1290 mm/compaction.c:3214
kthread+0x711/0x8a0 kernel/kthread.c:463
ret_from_fork+0x439/0x7d0 arch/x86/kernel/process.c:148
ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

Memory state around the buggy address:
ffff888041c23d00: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
ffff888041c23d80: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
>ffff888041c23e00: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
^
ffff888041c23e80: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
ffff888041c23f00: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
==================================================================

Tested on:

commit: 51a24b7d Merge tag 'trace-tools-v6.17-rc5' of git://gi..
git tree: upstream

console output: https://syzkaller.appspot.com/x/log.txt?x=15d8f2e2580000

kernel config: https://syzkaller.appspot.com/x/.config?x=bf99f2510ef92ba5
dashboard link: https://syzkaller.appspot.com/bug?extid=038b7bf43423e132b308
compiler: Debian clang version 20.1.8 (++20250708063551+0c9f909b7976-1~exp1~20250708183702.136), Debian LLD 20.1.8

patch: https://syzkaller.appspot.com/x/patch.diff?x=15ec3f12580000

[syzbot]

Hello,

syzbot has tested the proposed patch and the reproducer did not trigger any issue:

Reported-by: syzbot+038b7b...@syzkaller.appspotmail.com
Tested-by: syzbot+038b7b...@syzkaller.appspotmail.com

Tested on:

commit: 51a24b7d Merge tag 'trace-tools-v6.17-rc5' of git://gi..
git tree: upstream

console output: https://syzkaller.appspot.com/x/log.txt?x=10a04ae2580000

kernel config: https://syzkaller.appspot.com/x/.config?x=bf99f2510ef92ba5
dashboard link: https://syzkaller.appspot.com/bug?extid=038b7bf43423e132b308
compiler: Debian clang version 20.1.8 (++20250708063551+0c9f909b7976-1~exp1~20250708183702.136), Debian LLD 20.1.8

patch: https://syzkaller.appspot.com/x/patch.diff?x=17df8ae2580000

Note: testing is done by a robot and is best-effort only.

[syzbot]

Hello,

syzbot has tested the proposed patch and the reproducer did not trigger any issue:

Reported-by: syzbot+038b7b...@syzkaller.appspotmail.com
Tested-by: syzbot+038b7b...@syzkaller.appspotmail.com

Tested on:

commit: e5f0a698 Linux 6.17
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=12e426e2580000

kernel config: https://syzkaller.appspot.com/x/.config?x=bf99f2510ef92ba5
dashboard link: https://syzkaller.appspot.com/bug?extid=038b7bf43423e132b308
compiler: Debian clang version 20.1.8 (++20250708063551+0c9f909b7976-1~exp1~20250708183702.136), Debian LLD 20.1.8

patch: https://syzkaller.appspot.com/x/patch.diff?x=1755fae2580000

[syzbot]

Hello,

syzbot has tested the proposed patch and the reproducer did not trigger any issue:

Reported-by: syzbot+038b7b...@syzkaller.appspotmail.com
Tested-by: syzbot+038b7b...@syzkaller.appspotmail.com

Tested on:

commit: 30d4efb2 Merge tag 'for-linus-6.18-rc1-tag' of git://g..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=16b3f27c580000
kernel config: https://syzkaller.appspot.com/x/.config?x=607d55e4510cba63

dashboard link: https://syzkaller.appspot.com/bug?extid=038b7bf43423e132b308
compiler: Debian clang version 20.1.8 (++20250708063551+0c9f909b7976-1~exp1~20250708183702.136), Debian LLD 20.1.8

patch: https://syzkaller.appspot.com/x/patch.diff?x=13cb16e2580000

[syzbot]

Hello,

syzbot has tested the proposed patch and the reproducer did not trigger any issue:

Reported-by: syzbot+038b7b...@syzkaller.appspotmail.com
Tested-by: syzbot+038b7b...@syzkaller.appspotmail.com

Tested on:

commit: 30d4efb2 Merge tag 'for-linus-6.18-rc1-tag' of git://g..
git tree: upstream

console output: https://syzkaller.appspot.com/x/log.txt?x=155b05cd980000

kernel config: https://syzkaller.appspot.com/x/.config?x=607d55e4510cba63
dashboard link: https://syzkaller.appspot.com/bug?extid=038b7bf43423e132b308
compiler: Debian clang version 20.1.8 (++20250708063551+0c9f909b7976-1~exp1~20250708183702.136), Debian LLD 20.1.8

patch: https://syzkaller.appspot.com/x/patch.diff?x=14bbf27c580000