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BUG: KASAN: use-after-free in ext4_remove_blocks fs/ext4/extents.c:2516 [inline]
BUG: KASAN: use-after-free in ext4_ext_rm_leaf fs/ext4/extents.c:2716 [inline]
BUG: KASAN: use-after-free in ext4_ext_remove_space+0x26d9/0x4260 fs/ext4/extents.c:2965
Read of size 4 at addr ffff88804927b858 by task syz-executor/8062

CPU: 0 UID: 0 PID: 8062 Comm: syz-executor Not tainted syzkaller #0 PREEMPT_{RT,(full)} 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/24/2026
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_remove_blocks fs/ext4/extents.c:2516 [inline]
 ext4_ext_rm_leaf fs/ext4/extents.c:2716 [inline]
 ext4_ext_remove_space+0x26d9/0x4260 fs/ext4/extents.c:2965
 ext4_ext_truncate+0x17e/0x2f0 fs/ext4/extents.c:4484
 ext4_truncate+0xb64/0x1320 fs/ext4/inode.c:4612
 ext4_evict_inode+0x863/0xe60 fs/ext4/inode.c:260
 evict+0x61e/0xb10 fs/inode.c:837
 do_unlinkat+0x354/0x590 fs/namei.c:5452
 __do_sys_unlink fs/namei.c:5483 [inline]
 __se_sys_unlink fs/namei.c:5481 [inline]
 __x64_sys_unlink+0x47/0x50 fs/namei.c:5481
 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
RIP: 0033:0x7f2783609fa7
Code: 73 01 c3 48 c7 c1 e8 ff ff ff f7 d8 64 89 01 48 83 c8 ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 b8 57 00 00 00 0f 05 <48> 3d 00 f0 ff ff 77 01 c3 48 c7 c2 e8 ff ff ff f7 d8 64 89 02 b8
RSP: 002b:00007fffda3b03c8 EFLAGS: 00000206 ORIG_RAX: 0000000000000057
RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00007f2783609fa7
RDX: 00007fffda3b03f0 RSI: 00007fffda3b0480 RDI: 00007fffda3b0480
RBP: 00007fffda3b0480 R08: 00007fffda3b1480 R09: 00000000ffffffff
R10: 0000000000000100 R11: 0000000000000206 R12: 00007fffda3b1570
R13: 00007f278367471f R14: 000000000004a782 R15: 00007fffda3b2640
 </TASK>

The buggy address belongs to the physical page:
page: refcount:0 mapcount:0 mapping:0000000000000000 index:0x89 pfn:0x4927b
flags: 0x80000000000000(node=0|zone=1)
raw: 0080000000000000 ffffea0001249e88 ffffea0001847408 0000000000000000
raw: 0000000000000089 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 10707, tgid 10705 (syz.5.196), ts 302700409257, free_ts 307371734045
 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+0x28bb/0x2950 mm/page_alloc.c:3945
 __alloc_frozen_pages_noprof+0x18d/0x380 mm/page_alloc.c:5240
 alloc_pages_mpol+0xd1/0x380 mm/mempolicy.c:2486
 folio_alloc_mpol_noprof+0x39/0xe0 mm/mempolicy.c:2505
 shmem_alloc_folio mm/shmem.c:1913 [inline]
 shmem_alloc_and_add_folio mm/shmem.c:1955 [inline]
 shmem_get_folio_gfp+0x644/0x1a80 mm/shmem.c:2579
 shmem_get_folio mm/shmem.c:2685 [inline]
 shmem_write_begin+0x166/0x320 mm/shmem.c:3338
 generic_perform_write+0x2af/0x8b0 mm/filemap.c:4314
 shmem_file_write_iter+0xfb/0x120 mm/shmem.c:3513
 new_sync_write fs/read_write.c:593 [inline]
 vfs_write+0x629/0xba0 fs/read_write.c:686
 ksys_write+0x156/0x270 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 8975 tgid 8975 stack trace:
 reset_page_owner include/linux/page_owner.h:25 [inline]
 free_pages_prepare mm/page_alloc.c:1433 [inline]
 free_unref_folios+0xd5e/0x19d0 mm/page_alloc.c:3030
 folios_put_refs+0x56f/0x680 mm/swap.c:1002
 folio_batch_release include/linux/pagevec.h:101 [inline]
 shmem_undo_range+0x52e/0x1670 mm/shmem.c:1149
 shmem_truncate_range mm/shmem.c:1272 [inline]
 shmem_evict_inode+0x240/0x9e0 mm/shmem.c:1402
 evict+0x61e/0xb10 fs/inode.c:837
 __dentry_kill+0x1a2/0x5e0 fs/dcache.c:670
 finish_dput+0xc9/0x480 fs/dcache.c:879
 __fput+0x6a0/0xa80 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

Memory state around the buggy address:
 ffff88804927b700: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff88804927b780: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
>ffff88804927b800: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
                                                    ^
 ffff88804927b880: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff88804927b900: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
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