EXT4-fs (loop1): mounted filesystem without journal. Quota mode: writeback.
==================================================================
BUG: KASAN: use-after-free in ext4_ext_binsearch fs/ext4/extents.c:837 [inline]
BUG: KASAN: use-after-free in ext4_find_extent+0x994/0xb6c fs/ext4/extents.c:953
Read of size 4 at addr ffff0000f8627018 by task syz.1.27/4519

CPU: 0 PID: 4519 Comm: syz.1.27 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 06/30/2025
Call trace:
 dump_backtrace+0x1c8/0x1f4 arch/arm64/kernel/stacktrace.c:158
 show_stack+0x2c/0x3c arch/arm64/kernel/stacktrace.c:165
 __dump_stack+0x30/0x40 lib/dump_stack.c:88
 dump_stack_lvl+0xf8/0x160 lib/dump_stack.c:106
 print_address_description+0x88/0x218 mm/kasan/report.c:316
 print_report+0x50/0x68 mm/kasan/report.c:420
 kasan_report+0xa8/0x100 mm/kasan/report.c:524
 __asan_report_load4_noabort+0x2c/0x38 mm/kasan/report_generic.c:350
 ext4_ext_binsearch fs/ext4/extents.c:837 [inline]
 ext4_find_extent+0x994/0xb6c fs/ext4/extents.c:953
 ext4_ext_map_blocks+0x240/0x559c fs/ext4/extents.c:4166
 ext4_map_blocks+0x860/0x1770 fs/ext4/inode.c:679
 _ext4_get_block+0x194/0x4c8 fs/ext4/inode.c:822
 ext4_get_block+0x4c/0x60 fs/ext4/inode.c:839
 ext4_block_write_begin+0x508/0x10f8 fs/ext4/inode.c:1124
 ext4_write_begin+0x5ec/0x133c fs/ext4/ext4_jbd2.h:-1
 ext4_da_write_begin+0x360/0x9d8 fs/ext4/inode.c:3000
 generic_perform_write+0x230/0x4b0 mm/filemap.c:3846
 ext4_buffered_write_iter+0x2c4/0x530 fs/ext4/file.c:285
 ext4_file_write_iter+0x188/0x152c fs/ext4/file.c:-1
 call_write_iter include/linux/fs.h:2265 [inline]
 new_sync_write fs/read_write.c:491 [inline]
 vfs_write+0x5ac/0x7c4 fs/read_write.c:584
 ksys_write+0x120/0x210 fs/read_write.c:637
 __do_sys_write fs/read_write.c:649 [inline]
 __se_sys_write fs/read_write.c:646 [inline]
 __arm64_sys_write+0x7c/0x90 fs/read_write.c:646
 __invoke_syscall arch/arm64/kernel/syscall.c:38 [inline]
 invoke_syscall+0x98/0x2bc arch/arm64/kernel/syscall.c:52
 el0_svc_common+0x138/0x258 arch/arm64/kernel/syscall.c:140
 do_el0_svc+0x58/0x13c arch/arm64/kernel/syscall.c:204
 el0_svc+0x58/0x138 arch/arm64/kernel/entry-common.c:637
 el0t_64_sync_handler+0x84/0xf0 arch/arm64/kernel/entry-common.c:655
 el0t_64_sync+0x18c/0x190 arch/arm64/kernel/entry.S:585

The buggy address belongs to the physical page:
page:00000000ef90992d refcount:0 mapcount:0 mapping:0000000000000000 index:0x1 pfn:0x138627
flags: 0x5ffc00000000000(node=0|zone=2|lastcpupid=0x7ff)
raw: 05ffc00000000000 dead000000000100 dead000000000122 0000000000000000
raw: 0000000000000001 0000000000000000 00000000ffffffff 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff0000f8626f00: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff0000f8626f80: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
>ffff0000f8627000: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
                            ^
 ffff0000f8627080: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff0000f8627100: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
==================================================================
EXT4-fs error (device loop1): ext4_map_blocks:745: inode #15: block 4: comm syz.1.27: lblock 4 mapped to illegal pblock 4 (length 1)