EXT4-fs error (device loop0): mb_free_blocks:2037: group 0, inode 19: block 305:freeing already freed block (bit 19); block bitmap corrupt.
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BUG: KASAN: use-after-free in ext4_ext_rm_leaf fs/ext4/extents.c:2627 [inline]
BUG: KASAN: use-after-free in ext4_ext_remove_space+0x31b4/0x4260 fs/ext4/extents.c:2965
Read of size 4 at addr ffff888012ec2c18 by task syz.0.0/5330

CPU: 0 UID: 0 PID: 5330 Comm: syz.0.0 Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2 04/01/2014
Call Trace:
 <TASK>
 dump_stack_lvl+0xe8/0x150 lib/dump_stack.c:120
 print_address_description mm/kasan/report.c:378 [inline]
 print_report+0xba/0x230 mm/kasan/report.c:482
 kasan_report+0x117/0x150 mm/kasan/report.c:595
 ext4_ext_rm_leaf fs/ext4/extents.c:2627 [inline]
 ext4_ext_remove_space+0x31b4/0x4260 fs/ext4/extents.c:2965
 ext4_ext_truncate+0x17e/0x2f0 fs/ext4/extents.c:4484
 ext4_truncate+0xb63/0x1300 fs/ext4/inode.c:4612
 ext4_evict_inode+0x863/0xe60 fs/ext4/inode.c:260
 evict+0x61e/0xb10 fs/inode.c:837
 __dentry_kill+0x1a2/0x5e0 fs/dcache.c:670
 finish_dput+0xc9/0x480 fs/dcache.c:879
 __fput+0x691/0xa70 fs/file_table.c:476
 task_work_run+0x1d9/0x270 kernel/task_work.c:233
 resume_user_mode_work include/linux/resume_user_mode.h:50 [inline]
 __exit_to_user_mode_loop kernel/entry/common.c:44 [inline]
 exit_to_user_mode_loop+0xed/0x480 kernel/entry/common.c:75
 __exit_to_user_mode_prepare include/linux/irq-entry-common.h:226 [inline]
 syscall_exit_to_user_mode_prepare include/linux/irq-entry-common.h:256 [inline]
 syscall_exit_to_user_mode_work include/linux/entry-common.h:159 [inline]
 syscall_exit_to_user_mode include/linux/entry-common.h:194 [inline]
 do_syscall_64+0x2b7/0xf80 arch/x86/entry/syscall_64.c:100
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f0afc19acb9
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:00007ffcfbf96668 EFLAGS: 00000246 ORIG_RAX: 00000000000001b4
RAX: 0000000000000000 RBX: 00007ffcfbf96750 RCX: 00007f0afc19acb9
RDX: 0000000000000000 RSI: 000000000000001e RDI: 0000000000000003
RBP: 0000000000014c6e R08: 0000000000000001 R09: 0000000000000000
R10: 00007f0afbfff02c R11: 0000000000000246 R12: 00007ffcfbf96790
R13: 00007f0afc415fac R14: 00000000000153e1 R15: 00007f0afc415fa0
 </TASK>

The buggy address belongs to the physical page:
page: refcount:0 mapcount:0 mapping:0000000000000000 index:0x9bc pfn:0x12ec2
flags: 0xfff00000000000(node=0|zone=1|lastcpupid=0x7ff)
raw: 00fff00000000000 dead000000000100 dead000000000122 0000000000000000
raw: 00000000000009bc 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 5331, tgid 5330 (syz.0.0), ts 85978599564, free_ts 86399062283
 set_page_owner include/linux/page_owner.h:32 [inline]
 post_alloc_hook+0x228/0x280 mm/page_alloc.c:1884
 prep_new_page mm/page_alloc.c:1892 [inline]
 get_page_from_freelist+0x24dc/0x2580 mm/page_alloc.c:3945
 __alloc_frozen_pages_noprof+0x18d/0x380 mm/page_alloc.c:5240
 alloc_pages_mpol+0x232/0x4a0 mm/mempolicy.c:2486
 folio_alloc_mpol_noprof+0x39/0x70 mm/mempolicy.c:2505
 shmem_alloc_folio mm/shmem.c:1890 [inline]
 shmem_alloc_and_add_folio+0x445/0xf80 mm/shmem.c:1932
 shmem_get_folio_gfp+0x5a9/0x1670 mm/shmem.c:2556
 shmem_get_folio mm/shmem.c:2662 [inline]
 shmem_write_begin+0x16c/0x330 mm/shmem.c:3315
 generic_perform_write+0x2e2/0x8f0 mm/filemap.c:4314
 shmem_file_write_iter+0xf8/0x120 mm/shmem.c:3490
 new_sync_write fs/read_write.c:593 [inline]
 vfs_write+0x61d/0xb90 fs/read_write.c:686
 ksys_write+0x150/0x270 fs/read_write.c:738
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xe2/0xf80 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
page last free pid 79 tgid 79 stack trace:
 reset_page_owner include/linux/page_owner.h:25 [inline]
 free_pages_prepare mm/page_alloc.c:1433 [inline]
 free_unref_folios+0xdce/0x1510 mm/page_alloc.c:3030
 shrink_folio_list+0x2960/0x5160 mm/vmscan.c:1534
 evict_folios+0x4795/0x5880 mm/vmscan.c:4711
 try_to_shrink_lruvec+0x88b/0xb20 mm/vmscan.c:4874
 shrink_one+0x25c/0x710 mm/vmscan.c:4919
 shrink_many mm/vmscan.c:4982 [inline]
 lru_gen_shrink_node mm/vmscan.c:5060 [inline]
 shrink_node+0x2f8b/0x35f0 mm/vmscan.c:6047
 kswapd_shrink_node mm/vmscan.c:6901 [inline]
 balance_pgdat mm/vmscan.c:7084 [inline]
 kswapd+0x144c/0x2800 mm/vmscan.c:7354
 kthread+0x726/0x8b0 kernel/kthread.c:463
 ret_from_fork+0x51b/0xa40 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:246

Memory state around the buggy address:
 ffff888012ec2b00: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff888012ec2b80: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
>ffff888012ec2c00: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
                            ^
 ffff888012ec2c80: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff888012ec2d00: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
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