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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 ffff000121890018 by task syz.1.269/7894

CPU: 1 UID: 0 PID: 7894 Comm: syz.1.269 Not tainted syzkaller #0 PREEMPT 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/03/2025
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+0x230/0x54a4 fs/ext4/extents.c:4208
 ext4_map_create_blocks fs/ext4/inode.c:613 [inline]
 ext4_map_blocks+0x784/0x1548 fs/ext4/inode.c:816
 _ext4_get_block+0x194/0x4d4 fs/ext4/inode.c:916
 ext4_get_block_unwritten+0x3c/0x114 fs/ext4/inode.c:949
 ext4_block_write_begin+0x810/0x13f4 fs/ext4/inode.c:1203
 ext4_block_page_mkwrite fs/ext4/inode.c:6628 [inline]
 ext4_page_mkwrite+0x5e8/0xea8 fs/ext4/inode.c:6731
 do_page_mkwrite+0x138/0x2b8 mm/memory.c:3528
 wp_page_shared mm/memory.c:3929 [inline]
 do_wp_page+0x1d30/0x4158 mm/memory.c:4148
 handle_pte_fault mm/memory.c:6289 [inline]
 __handle_mm_fault mm/memory.c:6411 [inline]
 handle_mm_fault+0xff8/0x2678 mm/memory.c:6580
 do_page_fault+0x410/0x13cc arch/arm64/mm/fault.c:657
 do_mem_abort+0x70/0x194 arch/arm64/mm/fault.c:933
 el0_da+0x64/0x248 arch/arm64/kernel/entry-common.c:540
 el0t_64_sync_handler+0x90/0x12c arch/arm64/kernel/entry-common.c:746
 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:0xffffa4a43 pfn:0x161890
flags: 0x5ffc00000000000(node=0|zone=2|lastcpupid=0x7ff)
raw: 05ffc00000000000 dead000000000100 dead000000000122 0000000000000000
raw: 0000000ffffa4a43 0000000000000000 00000000ffffffff 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff00012188ff00: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff00012188ff80: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
>ffff000121890000: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
                            ^
 ffff000121890080: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff000121890100: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
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