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BUG: KASAN: use-after-free in ext4_ext_binsearch fs/ext4/extents.c:840 [inline]
BUG: KASAN: use-after-free in ext4_find_extent+0xb92/0xd80 fs/ext4/extents.c:955
Read of size 4 at addr ffff88805708c018 by task syz.4.33/6064

CPU: 0 UID: 0 PID: 6064 Comm: syz.4.33 Not tainted 6.14.0-syzkaller-03576-g1e1ba8d23dae #0 PREEMPT(full) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2025
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:94 [inline]
 dump_stack_lvl+0x241/0x360 lib/dump_stack.c:120
 print_address_description mm/kasan/report.c:408 [inline]
 print_report+0x16e/0x5b0 mm/kasan/report.c:521
 kasan_report+0x143/0x180 mm/kasan/report.c:634
 ext4_ext_binsearch fs/ext4/extents.c:840 [inline]
 ext4_find_extent+0xb92/0xd80 fs/ext4/extents.c:955
 ext4_ext_map_blocks+0x2e6/0x7d80 fs/ext4/extents.c:4205
 ext4_map_create_blocks fs/ext4/inode.c:516 [inline]
 ext4_map_blocks+0x909/0x1a70 fs/ext4/inode.c:702
 mpage_map_one_extent fs/ext4/inode.c:2219 [inline]
 mpage_map_and_submit_extent fs/ext4/inode.c:2272 [inline]
 ext4_do_writepages+0x21cd/0x3e00 fs/ext4/inode.c:2735
 ext4_writepages+0x203/0x3c0 fs/ext4/inode.c:2824
 do_writepages+0x36a/0x890 mm/page-writeback.c:2687
 filemap_fdatawrite_wbc mm/filemap.c:388 [inline]
 __filemap_fdatawrite_range mm/filemap.c:421 [inline]
 filemap_write_and_wait_range+0x2ac/0x3d0 mm/filemap.c:693
 __iomap_dio_rw+0xae4/0x26d0 fs/iomap/direct-io.c:654
 iomap_dio_rw+0x46/0xa0 fs/iomap/direct-io.c:823
 ext4_dio_read_iter fs/ext4/file.c:94 [inline]
 ext4_file_read_iter+0x513/0x670 fs/ext4/file.c:145
 copy_splice_read+0x63f/0xb50 fs/splice.c:363
 do_splice_read fs/splice.c:978 [inline]
 splice_direct_to_actor+0x4f0/0xc90 fs/splice.c:1083
 do_splice_direct_actor fs/splice.c:1201 [inline]
 do_splice_direct+0x281/0x3d0 fs/splice.c:1227
 do_sendfile+0x582/0x8c0 fs/read_write.c:1368
 __do_sys_sendfile64 fs/read_write.c:1429 [inline]
 __se_sys_sendfile64+0x17e/0x1e0 fs/read_write.c:1415
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xf3/0x230 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f3d8318d169
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:00007f3d84076038 EFLAGS: 00000246 ORIG_RAX: 0000000000000028
RAX: ffffffffffffffda RBX: 00007f3d833a5fa0 RCX: 00007f3d8318d169
RDX: 0000000000000000 RSI: 0000000000000005 RDI: 0000000000000005
RBP: 00007f3d8320e2a0 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000800000009 R11: 0000000000000246 R12: 0000000000000000
R13: 0000000000000000 R14: 00007f3d833a5fa0 R15: 00007ffd29ec9ca8
 </TASK>

The buggy address belongs to the physical page:
page: refcount:0 mapcount:0 mapping:0000000000000000 index:0x1049 pfn:0x5708c
flags: 0xfff00000000000(node=0|zone=1|lastcpupid=0x7ff)
raw: 00fff00000000000 dead000000000100 dead000000000122 0000000000000000
raw: 0000000000001049 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 5999, tgid 5998 (syz.2.22), ts 99977932166, free_ts 102333234347
 set_page_owner include/linux/page_owner.h:32 [inline]
 post_alloc_hook+0x1f4/0x240 mm/page_alloc.c:1551
 prep_new_page mm/page_alloc.c:1559 [inline]
 get_page_from_freelist+0x368a/0x37d0 mm/page_alloc.c:3477
 __alloc_frozen_pages_noprof+0x2c5/0x7b0 mm/page_alloc.c:4740
 alloc_pages_mpol+0x339/0x690 mm/mempolicy.c:2301
 folio_alloc_mpol_noprof+0x36/0x70 mm/mempolicy.c:2320
 shmem_alloc_folio mm/shmem.c:1863 [inline]
 shmem_alloc_and_add_folio+0x490/0x1070 mm/shmem.c:1902
 shmem_get_folio_gfp+0x655/0x1800 mm/shmem.c:2545
 shmem_get_folio mm/shmem.c:2651 [inline]
 shmem_write_begin+0x17e/0x3a0 mm/shmem.c:3301
 generic_perform_write+0x329/0xa10 mm/filemap.c:4102
 shmem_file_write_iter+0xf9/0x120 mm/shmem.c:3477
 new_sync_write fs/read_write.c:591 [inline]
 vfs_write+0x70f/0xd10 fs/read_write.c:684
 ksys_write+0x19d/0x2d0 fs/read_write.c:736
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xf3/0x230 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
page last free pid 5826 tgid 5826 stack trace:
 reset_page_owner include/linux/page_owner.h:25 [inline]
 free_pages_prepare mm/page_alloc.c:1127 [inline]
 free_unref_folios+0xe5b/0x18d0 mm/page_alloc.c:2707
 folios_put_refs+0x779/0x880 mm/swap.c:994
 folio_batch_release include/linux/pagevec.h:101 [inline]
 shmem_undo_range+0x595/0x1820 mm/shmem.c:1112
 shmem_truncate_range mm/shmem.c:1224 [inline]
 shmem_evict_inode+0x29d/0xa80 mm/shmem.c:1352
 evict+0x4f9/0x9b0 fs/inode.c:810
 __dentry_kill+0x20d/0x630 fs/dcache.c:643
 dput+0x19f/0x2b0 fs/dcache.c:885
 __fput+0x60b/0x9f0 fs/file_table.c:473
 task_work_run+0x251/0x310 kernel/task_work.c:227
 resume_user_mode_work include/linux/resume_user_mode.h:50 [inline]
 exit_to_user_mode_loop kernel/entry/common.c:114 [inline]
 exit_to_user_mode_prepare include/linux/entry-common.h:329 [inline]
 __syscall_exit_to_user_mode_work kernel/entry/common.c:207 [inline]
 syscall_exit_to_user_mode+0x13f/0x340 kernel/entry/common.c:218
 do_syscall_64+0x100/0x230 arch/x86/entry/syscall_64.c:100
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

Memory state around the buggy address:
 ffff88805708bf00: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff88805708bf80: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
>ffff88805708c000: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
                            ^
 ffff88805708c080: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff88805708c100: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
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