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BUG: KASAN: use-after-free in ext4_find_extent+0xae6/0xcc0
Read of size 4 at addr ffff888111bd7d18 by task syz.6.449/9406

CPU: 0 UID: 0 PID: 9406 Comm: syz.6.449 Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.2-debian-1.16.2-1 04/01/2014
Call Trace:
 <TASK>
 dump_stack_lvl+0x189/0x250
 print_report+0xca/0x240
 kasan_report+0x118/0x150
 ext4_find_extent+0xae6/0xcc0
 ext4_ext_remove_space+0x451/0x42f0
 ext4_punch_hole+0x875/0xd50
 ext4_fallocate+0x370/0x3d0
 vfs_fallocate+0x669/0x7e0
 file_ioctl+0x611/0x780
 do_vfs_ioctl+0xb33/0x1430
 __se_sys_ioctl+0x82/0x170
 do_syscall_64+0xfa/0x3b0
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f47c638eba9
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:00007f47c71b4038 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00007f47c65d5fa0 RCX: 00007f47c638eba9
RDX: 0000200000000240 RSI: 0000000040305829 RDI: 0000000000000004
RBP: 00007f47c6411e19 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f47c65d6038 R14: 00007f47c65d5fa0 R15: 00007ffc6d4d5c98
 </TASK>

The buggy address belongs to the physical page:
page: refcount:0 mapcount:0 mapping:0000000000000000 index:0xae9 pfn:0x111bd7
flags: 0x57ff00000000000(node=1|zone=2|lastcpupid=0x7ff)
raw: 057ff00000000000 ffffea000446f588 ffffea000471c008 0000000000000000
raw: 0000000000000ae9 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 9406, tgid 9404 (syz.6.449), ts 215535065074, free_ts 215847259691
 post_alloc_hook+0x240/0x2a0
 get_page_from_freelist+0x21e4/0x22c0
 __alloc_frozen_pages_noprof+0x181/0x370
 alloc_pages_mpol+0x232/0x4a0
 folio_alloc_mpol_noprof+0x39/0x70
 shmem_alloc_and_add_folio+0x447/0xf60
 shmem_get_folio_gfp+0x59d/0x1660
 shmem_write_begin+0xf7/0x2b0
 generic_perform_write+0x2c5/0x900
 shmem_file_write_iter+0xf8/0x120
 vfs_write+0x5c9/0xb30
 ksys_write+0x145/0x250
 do_syscall_64+0xfa/0x3b0
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
page last free pid 9406 tgid 9404 stack trace:
 free_unref_folios+0xdbd/0x1520
 folios_put_refs+0x559/0x640
 shmem_undo_range+0x49e/0x14b0
 shmem_evict_inode+0x272/0xa70
 evict+0x504/0x9c0
 __dentry_kill+0x209/0x660
 dput+0x19f/0x2b0
 __fput+0x68e/0xa70
 fput_close_sync+0x119/0x200
 __x64_sys_close+0x7f/0x110
 do_syscall_64+0xfa/0x3b0
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

Memory state around the buggy address:
 ffff888111bd7c00: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff888111bd7c80: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
>ffff888111bd7d00: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
                            ^
 ffff888111bd7d80: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff888111bd7e00: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
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