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BUG: KASAN: use-after-free in ext4_ext_binsearch fs/ext4/extents.c:827 [inline]
BUG: KASAN: use-after-free in ext4_find_extent+0xbeb/0xe20 fs/ext4/extents.c:946
Read of size 4 at addr ffff888131872ca8 by task syz.5.16/522

CPU: 1 PID: 522 Comm: syz.5.16 Not tainted 5.15.185-syzkaller-1080761-g5cf73bface18 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/07/2025
Call Trace:
 <TASK>
 __dump_stack+0x21/0x30 lib/dump_stack.c:88
 dump_stack_lvl+0xee/0x150 lib/dump_stack.c:106
 print_address_description+0x7f/0x2c0 mm/kasan/report.c:248
 __kasan_report mm/kasan/report.c:427 [inline]
 kasan_report+0xf1/0x140 mm/kasan/report.c:444
 __asan_report_load4_noabort+0x14/0x20 mm/kasan/report_generic.c:308
 ext4_ext_binsearch fs/ext4/extents.c:827 [inline]
 ext4_find_extent+0xbeb/0xe20 fs/ext4/extents.c:946
 ext4_ext_map_blocks+0x1de/0x6270 fs/ext4/extents.c:4165
 ext4_map_blocks+0x97b/0x1b20 fs/ext4/inode.c:674
 _ext4_get_block+0x1da/0x4e0 fs/ext4/inode.c:817
 ext4_get_block+0x39/0x50 fs/ext4/inode.c:834
 ext4_block_write_begin+0x556/0x1150 fs/ext4/inode.c:1102
 ext4_write_begin+0x638/0x1220 fs/ext4/ext4_jbd2.h:-1
 ext4_da_write_begin+0x2fa/0xb60 fs/ext4/inode.c:2988
 generic_perform_write+0x2ad/0x670 mm/filemap.c:3869
 ext4_buffered_write_iter+0x4ed/0x670 fs/ext4/file.c:270
 ext4_file_write_iter+0x18c/0x14c0 fs/ext4/file.c:664
 call_write_iter include/linux/fs.h:2212 [inline]
 new_sync_write fs/read_write.c:507 [inline]
 vfs_write+0x802/0xf70 fs/read_write.c:594
 ksys_write+0x140/0x240 fs/read_write.c:647
 __do_sys_write fs/read_write.c:659 [inline]
 __se_sys_write fs/read_write.c:656 [inline]
 __x64_sys_write+0x7b/0x90 fs/read_write.c:656
 x64_sys_call+0x8ef/0x9a0 arch/x86/include/generated/asm/syscalls_64.h:2
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x66/0xd0
RIP: 0033:0x7f813aeb7929
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:00007f813a907038 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 00007f813b0df080 RCX: 00007f813aeb7929
RDX: 0000000000040010 RSI: 0000200000000180 RDI: 0000000000000006
RBP: 00007f813af39b39 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 0000000000000000 R14: 00007f813b0df080 R15: 00007ffc93a4e418
 </TASK>

The buggy address belongs to the page:
page:ffffea0004c61c80 refcount:0 mapcount:0 mapping:0000000000000000 index:0x1 pfn:0x131872
flags: 0x4000000000000000(zone=1)
raw: 4000000000000000 ffffea0004c61cc8 ffffea0004c61c48 0000000000000000
raw: 0000000000000001 0000000000000000 00000000ffffffff 0000000000000000
page dumped because: kasan: bad access detected
page_owner info is not present (never set?)

Memory state around the buggy address:
 ffff888131872b80: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff888131872c00: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
>ffff888131872c80: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
                                  ^
 ffff888131872d00: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff888131872d80: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
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