EXT4-fs error (device loop5): ext4_mb_release_inode_pa:4902: group 0, free 0, pa_free 1
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BUG: KASAN: use-after-free in ext4_ext_rm_leaf fs/ext4/extents.c:2601 [inline]
BUG: KASAN: use-after-free in ext4_ext_remove_space+0x3496/0x40d0 fs/ext4/extents.c:2939
Read of size 4 at addr ffff888131fa5c18 by task syz.5.28/439

CPU: 1 PID: 439 Comm: syz.5.28 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 03/18/2026
Call Trace:
 <TASK>
 __dump_stack+0x21/0x30 lib/dump_stack.c:88
 dump_stack_lvl+0x110/0x170 lib/dump_stack.c:106
 print_address_description+0x7f/0x2c0 mm/kasan/report.c:248
 __kasan_report mm/kasan/report.c:427 [inline]
 kasan_report+0xf1/0x140 mm/kasan/report.c:444
 __asan_report_load4_noabort+0x14/0x20 mm/kasan/report_generic.c:308
 ext4_ext_rm_leaf fs/ext4/extents.c:2601 [inline]
 ext4_ext_remove_space+0x3496/0x40d0 fs/ext4/extents.c:2939
 ext4_ext_truncate+0x1a3/0x250 fs/ext4/extents.c:4479
 ext4_truncate+0x9be/0xfb0 fs/ext4/inode.c:4287
 ext4_truncate_failed_write fs/ext4/truncate.h:22 [inline]
 ext4_write_begin+0xad4/0x12e0 fs/ext4/inode.c:1276
 ext4_da_write_begin+0x321/0xbf0 fs/ext4/inode.c:2988
 generic_perform_write+0x2b7/0x690 mm/filemap.c:3870
 ext4_buffered_write_iter+0x4ed/0x670 fs/ext4/file.c:270
 ext4_file_write_iter+0x440/0x1540 fs/ext4/file.c:-1
 call_write_iter include/linux/fs.h:2212 [inline]
 new_sync_write fs/read_write.c:507 [inline]
 vfs_write+0x835/0xfd0 fs/read_write.c:594
 ksys_pwrite64 fs/read_write.c:701 [inline]
 __do_sys_pwrite64 fs/read_write.c:711 [inline]
 __se_sys_pwrite64 fs/read_write.c:708 [inline]
 __x64_sys_pwrite64+0x197/0x220 fs/read_write.c:708
 x64_sys_call+0xa6/0x9a0 arch/x86/include/generated/asm/syscalls_64.h:19
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x66/0xd0
RIP: 0033:0x7fb559974819
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:00007fb5597d7028 EFLAGS: 00000246 ORIG_RAX: 0000000000000012
RAX: ffffffffffffffda RBX: 00007fb559bedfa0 RCX: 00007fb559974819
RDX: 00000000200000c1 RSI: 00002000000000c0 RDI: 0000000000000004
RBP: 00007fb559a0ac91 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000009000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fb559bee038 R14: 00007fb559bedfa0 R15: 00007ffc21084488
 </TASK>

The buggy address belongs to the page:
page:ffffea0004c7e940 refcount:0 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x131fa5
flags: 0x4000000000000000(zone=1)
raw: 4000000000000000 ffffea0004c7e948 ffffea0004c7e948 0000000000000000
raw: 0000000000000000 0000000000000000 00000000ffffffff 0000000000000000
page dumped because: kasan: bad access detected
page_owner info is not present (never set?)

Memory state around the buggy address:
 ffff888131fa5b00: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff888131fa5b80: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
>ffff888131fa5c00: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
                            ^
 ffff888131fa5c80: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff888131fa5d00: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
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