==================================================================
BUG: KASAN: use-after-free in ext4_ext_binsearch_idx fs/ext4/extents.c:796 [inline]
BUG: KASAN: use-after-free in ext4_find_extent+0x7a9/0xda0 fs/ext4/extents.c:958
Read of size 4 at addr ffff8881d962f7d8 by task syz-executor.0/343

CPU: 0 PID: 343 Comm: syz-executor.0 Not tainted 5.4.233-syzkaller-00043-g0108362f3305 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 03/30/2023
Call Trace:
 __dump_stack lib/dump_stack.c:77 [inline]
 dump_stack+0x1d8/0x241 lib/dump_stack.c:118
 print_address_description+0x8c/0x600 mm/kasan/report.c:384
 __kasan_report+0xf3/0x120 mm/kasan/report.c:516
 kasan_report+0x30/0x60 mm/kasan/common.c:653
 ext4_ext_binsearch_idx fs/ext4/extents.c:796 [inline]
 ext4_find_extent+0x7a9/0xda0 fs/ext4/extents.c:958
 ext4_clu_mapped+0xe3/0x7c0 fs/ext4/extents.c:6034
 ext4_insert_delayed_block fs/ext4/inode.c:1840 [inline]
 ext4_da_map_blocks fs/ext4/inode.c:1951 [inline]
 ext4_da_get_block_prep+0xa26/0x13f0 fs/ext4/inode.c:2015
 ext4_block_write_begin+0x685/0x1180 fs/ext4/inode.c:1223
 ext4_da_write_begin+0x7c9/0xfe0 fs/ext4/inode.c:3185
 generic_perform_write+0x2c7/0x560 mm/filemap.c:3311
 __generic_file_write_iter+0x239/0x490 mm/filemap.c:3440
 ext4_file_write_iter+0x499/0x10e0 fs/ext4/file.c:270
 call_write_iter include/linux/fs.h:1981 [inline]
 new_sync_write fs/read_write.c:483 [inline]
 __vfs_write+0x5d3/0x750 fs/read_write.c:496
 vfs_write+0x206/0x4e0 fs/read_write.c:558
 ksys_write+0x199/0x2c0 fs/read_write.c:611
 do_syscall_64+0xca/0x1c0 arch/x86/entry/common.c:290
 entry_SYSCALL_64_after_hwframe+0x5c/0xc1

The buggy address belongs to the page:
page:ffffea0007658bc0 refcount:0 mapcount:0 mapping:0000000000000000 index:0x0
flags: 0x8000000000000000()
raw: 8000000000000000 ffffea0007658bc8 ffffea0007658bc8 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:
 ffff8881d962f680: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff8881d962f700: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
>ffff8881d962f780: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
                                                    ^
 ffff8881d962f800: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff8881d962f880: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
==================================================================
EXT4-fs error (device loop0): ext4_find_extent:963: inode #15: comm syz-executor.0: pblk 0 bad header/extent: invalid magic - magic 0, entries 0, max 0(0), depth 0(3)