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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+0xbcc/0xe00 fs/ext4/extents.c:946
Read of size 4 at addr ffff88806ec07070 by task syz-executor.0/4625

CPU: 0 PID: 4625 Comm: syz-executor.0 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 08/18/2025
Call Trace:
 <TASK>
 dump_stack_lvl+0x168/0x230 lib/dump_stack.c:106
 print_address_description+0x60/0x2d0 mm/kasan/report.c:248
 __kasan_report mm/kasan/report.c:434 [inline]
 kasan_report+0xdf/0x130 mm/kasan/report.c:451
 ext4_ext_binsearch fs/ext4/extents.c:827 [inline]
 ext4_find_extent+0xbcc/0xe00 fs/ext4/extents.c:946
 ext4_ext_map_blocks+0x25a/0x64e0 fs/ext4/extents.c:4166
 ext4_map_blocks+0x981/0x1b30 fs/ext4/inode.c:673
 _ext4_get_block+0x1d7/0x4e0 fs/ext4/inode.c:816
 __block_write_begin_int+0x54e/0x15a0 fs/buffer.c:2012
 __block_write_begin fs/buffer.c:2062 [inline]
 block_page_mkwrite+0x210/0x280 fs/buffer.c:2525
 ext4_page_mkwrite+0x3ed/0x1240 fs/ext4/inode.c:6235
 do_page_mkwrite+0x168/0x3c0 mm/memory.c:2922
 wp_page_shared+0x16b/0x6d0 mm/memory.c:3259
 handle_pte_fault mm/memory.c:4668 [inline]
 __handle_mm_fault mm/memory.c:4785 [inline]
 handle_mm_fault+0x1eca/0x43c0 mm/memory.c:4883
 do_user_addr_fault+0x489/0xc80 arch/x86/mm/fault.c:1357
 handle_page_fault arch/x86/mm/fault.c:1445 [inline]
 exc_page_fault+0x60/0x100 arch/x86/mm/fault.c:1501
 asm_exc_page_fault+0x22/0x30 arch/x86/include/asm/idtentry.h:606
RIP: 0033:0x7f509fbd4cc7
Code: ce 48 ff c7 48 01 fe 48 8d 54 11 80 0f 1f 80 00 00 00 00 c5 fe 6f 0e c5 fe 6f 56 20 c5 fe 6f 5e 40 c5 fe 6f 66 60 48 83 ee 80 <c5> fd 7f 0f c5 fd 7f 57 20 c5 fd 7f 5f 40 c5 fd 7f 67 60 48 83 ef
RSP: 002b:00007ffd274c83b8 EFLAGS: 00010203
RAX: 0000000020003600 RBX: 00007ffd274c84c8 RCX: 0000000020003600
RDX: 00000000200036a9 RSI: 00007f509f7977b0 RDI: 0000000020003620
RBP: 0000000000000001 R08: 0000000000000000 R09: 00007f509fd12f8c
R10: 00007ffd274c84f0 R11: 0000000000000246 R12: 00007f509f7976f0
R13: fffffffffffffffe R14: 00007f509f777000 R15: 00007f509f7976f8
 </TASK>

The buggy address belongs to the page:
page:ffffea0001bb01c0 refcount:0 mapcount:0 mapping:0000000000000000 index:0x1 pfn:0x6ec07
flags: 0xfff00000000000(node=0|zone=1|lastcpupid=0x7ff)
raw: 00fff00000000000 ffffea0001bafc48 ffffea0001babcc8 0000000000000000
raw: 0000000000000001 0000000000000000 00000000ffffffff 0000000000000000
page dumped because: kasan: bad access detected
page_owner tracks the page as freed
page last allocated via order 0, migratetype Movable, gfp_mask 0x1100dca(GFP_HIGHUSER_MOVABLE|__GFP_ZERO), pid 4632, ts 74912113159, free_ts 74915317474
 prep_new_page mm/page_alloc.c:2426 [inline]
 get_page_from_freelist+0x1b77/0x1c60 mm/page_alloc.c:4192
 __alloc_pages+0x1e1/0x470 mm/page_alloc.c:5487
 alloc_pages_vma+0x393/0x7c0 mm/mempolicy.c:2146
 do_anonymous_page mm/memory.c:3838 [inline]
 handle_pte_fault mm/memory.c:4648 [inline]
 __handle_mm_fault mm/memory.c:4785 [inline]
 handle_mm_fault+0x2382/0x43c0 mm/memory.c:4883
 do_user_addr_fault+0x489/0xc80 arch/x86/mm/fault.c:1357
 handle_page_fault arch/x86/mm/fault.c:1445 [inline]
 exc_page_fault+0x60/0x100 arch/x86/mm/fault.c:1501
 asm_exc_page_fault+0x22/0x30 arch/x86/include/asm/idtentry.h:606
page last free stack trace:
 reset_page_owner include/linux/page_owner.h:24 [inline]
 free_pages_prepare mm/page_alloc.c:1340 [inline]
 free_pcp_prepare mm/page_alloc.c:1391 [inline]
 free_unref_page_prepare+0x637/0x6c0 mm/page_alloc.c:3317
 free_unref_page_list+0x122/0x7e0 mm/page_alloc.c:3433
 release_pages+0x184b/0x1bb0 mm/swap.c:963
 tlb_batch_pages_flush mm/mmu_gather.c:49 [inline]
 tlb_flush_mmu_free mm/mmu_gather.c:240 [inline]
 tlb_flush_mmu mm/mmu_gather.c:247 [inline]
 tlb_finish_mmu+0x164/0x2e0 mm/mmu_gather.c:338
 exit_mmap+0x3a6/0x5f0 mm/mmap.c:3218
 __mmput+0x115/0x3b0 kernel/fork.c:1127
 exit_mm+0x567/0x6c0 kernel/exit.c:550
 do_exit+0x5a1/0x20a0 kernel/exit.c:870
 do_group_exit+0x12e/0x300 kernel/exit.c:997
 __do_sys_exit_group kernel/exit.c:1008 [inline]
 __se_sys_exit_group kernel/exit.c:1006 [inline]
 __x64_sys_exit_group+0x3b/0x40 kernel/exit.c:1006
 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

Memory state around the buggy address:
 ffff88806ec06f00: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff88806ec06f80: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
>ffff88806ec07000: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
                                                             ^
 ffff88806ec07080: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff88806ec07100: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
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