==================================================================
BUG: KASAN: use-after-free in ext4_ext_binsearch fs/ext4/extents.c:841 [inline]
BUG: KASAN: use-after-free in ext4_find_extent+0x8dc/0xa8c fs/ext4/extents.c:956
Read of size 4 at addr ffff000108d53d18 by task syz.2.235/8170

CPU: 0 UID: 0 PID: 8170 Comm: syz.2.235 Not tainted syzkaller #0 PREEMPT 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 06/30/2025
Call trace:
 show_stack+0x2c/0x3c arch/arm64/kernel/stacktrace.c:499 (C)
 __dump_stack+0x30/0x40 lib/dump_stack.c:94
 dump_stack_lvl+0xd8/0x12c lib/dump_stack.c:120
 print_address_description+0xa8/0x238 mm/kasan/report.c:378
 print_report+0x68/0x84 mm/kasan/report.c:482
 kasan_report+0xb0/0x110 mm/kasan/report.c:595
 __asan_report_load4_noabort+0x20/0x2c mm/kasan/report_generic.c:380
 ext4_ext_binsearch fs/ext4/extents.c:841 [inline]
 ext4_find_extent+0x8dc/0xa8c fs/ext4/extents.c:956
 ext4_ext_map_blocks+0x258/0x5494 fs/ext4/extents.c:4208
 ext4_map_create_blocks fs/ext4/inode.c:609 [inline]
 ext4_map_blocks+0x6f0/0x14a8 fs/ext4/inode.c:811
 _ext4_get_block+0x19c/0x4e0 fs/ext4/inode.c:910
 ext4_get_block_unwritten+0x3c/0x114 fs/ext4/inode.c:943
 ext4_block_write_begin+0x7ac/0x1328 fs/ext4/inode.c:1198
 ext4_write_begin+0x928/0x14fc fs/ext4/ext4_jbd2.h:-1
 ext4_da_write_begin+0x28c/0xc28 fs/ext4/inode.c:3129
 generic_perform_write+0x244/0x7bc mm/filemap.c:4175
 ext4_buffered_write_iter+0x2b8/0x528 fs/ext4/file.c:299
 ext4_file_write_iter+0x1d8/0x1864 fs/ext4/file.c:-1
 do_iter_readv_writev+0x4c0/0x724 fs/read_write.c:-1
 vfs_writev+0x29c/0x7cc fs/read_write.c:1057
 do_writev+0x128/0x290 fs/read_write.c:1103
 __do_sys_writev fs/read_write.c:1171 [inline]
 __se_sys_writev fs/read_write.c:1168 [inline]
 __arm64_sys_writev+0x80/0x94 fs/read_write.c:1168
 __invoke_syscall arch/arm64/kernel/syscall.c:35 [inline]
 invoke_syscall+0x98/0x254 arch/arm64/kernel/syscall.c:49
 el0_svc_common+0x130/0x23c arch/arm64/kernel/syscall.c:132
 do_el0_svc+0x48/0x58 arch/arm64/kernel/syscall.c:151
 el0_svc+0x5c/0x254 arch/arm64/kernel/entry-common.c:744
 el0t_64_sync_handler+0x84/0x12c arch/arm64/kernel/entry-common.c:763
 el0t_64_sync+0x198/0x19c arch/arm64/kernel/entry.S:596

The buggy address belongs to the physical page:
page: refcount:0 mapcount:0 mapping:0000000000000000 index:0xaad pfn:0x148d53
flags: 0x5ffc00000000000(node=0|zone=2|lastcpupid=0x7ff)
raw: 05ffc00000000000 fffffdffc4235508 fffffdffc4235488 0000000000000000
raw: 0000000000000aad 0000000000000000 00000000ffffffff 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff000108d53c00: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff000108d53c80: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
>ffff000108d53d00: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
                            ^
 ffff000108d53d80: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff000108d53e00: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
==================================================================
EXT4-fs error (device loop2): ext4_ext_split:1079: inode #15: comm syz.2.235: p_ext > EXT_MAX_EXTENT!
EXT4-fs error (device loop2): mb_free_blocks:2017: group 0, inode 15: block 177:freeing already freed block (bit 11); block bitmap corrupt.
EXT4-fs (loop2): Delayed block allocation failed for inode 15 at logical offset 0 with max blocks 1 with error 28
EXT4-fs (loop2): This should not happen!! Data will be lost

EXT4-fs (loop2): Total free blocks count 0
EXT4-fs (loop2): Free/Dirty block details
EXT4-fs (loop2): free_blocks=32
EXT4-fs (loop2): dirty_blocks=0
EXT4-fs (loop2): Block reservation details
EXT4-fs (loop2): i_reserved_data_blocks=0