==================================================================
BUG: KASAN: use-after-free in ext4_ext_binsearch fs/ext4/extents.c:827 [inline]
BUG: KASAN: use-after-free in ext4_find_extent+0x994/0xb6c fs/ext4/extents.c:946
Read of size 4 at addr ffff0000deda9c70 by task syz.5.639/8131

CPU: 1 PID: 8131 Comm: syz.5.639 Not tainted 5.15.181-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/19/2025
Call trace:
 dump_backtrace+0x0/0x43c arch/arm64/kernel/stacktrace.c:152
 show_stack+0x2c/0x3c arch/arm64/kernel/stacktrace.c:216
 __dump_stack+0x30/0x40 lib/dump_stack.c:88
 dump_stack_lvl+0xf8/0x160 lib/dump_stack.c:106
 print_address_description+0x78/0x30c mm/kasan/report.c:248
 __kasan_report mm/kasan/report.c:434 [inline]
 kasan_report+0xec/0x15c mm/kasan/report.c:451
 __asan_report_load4_noabort+0x44/0x50 mm/kasan/report_generic.c:308
 ext4_ext_binsearch fs/ext4/extents.c:827 [inline]
 ext4_find_extent+0x994/0xb6c fs/ext4/extents.c:946
 ext4_ext_map_blocks+0x234/0x5628 fs/ext4/extents.c:4165
 ext4_map_blocks+0x2e8/0x167c fs/ext4/inode.c:600
 _ext4_get_block+0x190/0x4ec fs/ext4/inode.c:816
 ext4_get_block_unwritten+0x38/0x4c fs/ext4/inode.c:847
 ext4_block_write_begin+0x528/0x1110 fs/ext4/inode.c:1101
 ext4_write_begin+0x5d0/0xdbc fs/ext4/ext4_jbd2.h:-1
 ext4_da_write_begin+0x380/0x83c fs/ext4/inode.c:2975
 generic_perform_write+0x204/0x480 mm/filemap.c:3785
 ext4_buffered_write_iter+0x408/0x538 fs/ext4/file.c:268
 ext4_file_write_iter+0x698/0x14cc include/linux/fs.h:-1
 call_write_iter include/linux/fs.h:2172 [inline]
 new_sync_write fs/read_write.c:507 [inline]
 vfs_write+0x7c8/0xa2c fs/read_write.c:594
 ksys_pwrite64 fs/read_write.c:701 [inline]
 __do_sys_pwrite64 fs/read_write.c:711 [inline]
 __se_sys_pwrite64 fs/read_write.c:708 [inline]
 __arm64_sys_pwrite64+0x170/0x200 fs/read_write.c:708
 __invoke_syscall arch/arm64/kernel/syscall.c:38 [inline]
 invoke_syscall+0x98/0x2b8 arch/arm64/kernel/syscall.c:52
 el0_svc_common+0x138/0x258 arch/arm64/kernel/syscall.c:142
 do_el0_svc+0x58/0x14c arch/arm64/kernel/syscall.c:181
 el0_svc+0x78/0x1e0 arch/arm64/kernel/entry-common.c:608
 el0t_64_sync_handler+0xcc/0xe4 arch/arm64/kernel/entry-common.c:626
 el0t_64_sync+0x1a0/0x1a4 arch/arm64/kernel/entry.S:584

The buggy address belongs to the page:
page:00000000a7b0d052 refcount:0 mapcount:0 mapping:0000000000000000 index:0x100 pfn:0x11eda9
flags: 0x5ffc00000000000(node=0|zone=2|lastcpupid=0x7ff)
raw: 05ffc00000000000 dead000000000100 dead000000000122 0000000000000000
raw: 0000000000000100 0000000000000000 00000000ffffffff 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff0000deda9b00: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff0000deda9b80: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
>ffff0000deda9c00: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
                                                             ^
 ffff0000deda9c80: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff0000deda9d00: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
==================================================================
EXT4-fs error (device loop5): ext4_map_blocks:629: inode #15: block 131075: comm syz.5.639: lblock 131075 mapped to illegal pblock 131075 (length 1)