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BUG: KASAN: use-after-free in ext4_ext_rm_leaf fs/ext4/extents.c:2601 [inline]
BUG: KASAN: use-after-free in ext4_ext_remove_space+0x353c/0x4180 fs/ext4/extents.c:2939
Read of size 4 at addr ffff8881324bdc18 by task syz-executor/4035

CPU: 0 PID: 4035 Comm: syz-executor Tainted: G        W         syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 08/18/2025
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_rm_leaf fs/ext4/extents.c:2601 [inline]
 ext4_ext_remove_space+0x353c/0x4180 fs/ext4/extents.c:2939
 ext4_ext_truncate+0x1a3/0x250 fs/ext4/extents.c:4473
 ext4_truncate+0x9a6/0xfa0 fs/ext4/inode.c:4281
 ext4_evict_inode+0xcb9/0x1450 fs/ext4/inode.c:290
 evict+0x485/0x870 fs/inode.c:650
 iput_final fs/inode.c:1779 [inline]
 iput+0x635/0x7c0 fs/inode.c:1805
 do_unlinkat+0x375/0x6b0 fs/namei.c:4355
 __do_sys_unlink fs/namei.c:4396 [inline]
 __se_sys_unlink fs/namei.c:4394 [inline]
 __x64_sys_unlink+0x49/0x50 fs/namei.c:4394
 x64_sys_call+0x878/0x9a0 arch/x86/include/generated/asm/syscalls_64.h:88
 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: 0033:0x7f4fd58ec157
Code: 73 01 c3 48 c7 c1 a8 ff ff ff f7 d8 64 89 01 48 83 c8 ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 b8 57 00 00 00 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:00007ffcd8439ec8 EFLAGS: 00000206 ORIG_RAX: 0000000000000057
RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00007f4fd58ec157
RDX: 00007ffcd8439ef0 RSI: 00007ffcd8439f80 RDI: 00007ffcd8439f80
RBP: 00007ffcd8439f80 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000100 R11: 0000000000000206 R12: 00007ffcd843b070
R13: 00007f4fd596fc05 R14: 0000000000064685 R15: 00007ffcd843c140
 </TASK>

The buggy address belongs to the page:
page:ffffea0004c92f40 refcount:0 mapcount:0 mapping:0000000000000000 index:0x100 pfn:0x1324bd
flags: 0x4000000000000000(zone=1)
raw: 4000000000000000 dead000000000100 dead000000000122 0000000000000000
raw: 0000000000000100 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 0x100dca(GFP_HIGHUSER_MOVABLE|__GFP_ZERO), pid 8100, ts 352769621819, free_ts 352976752900
 set_page_owner include/linux/page_owner.h:33 [inline]
 post_alloc_hook+0x192/0x1b0 mm/page_alloc.c:2605
 prep_new_page+0x1c/0x110 mm/page_alloc.c:2611
 get_page_from_freelist+0x2cc5/0x2d50 mm/page_alloc.c:4485
 __alloc_pages+0x18f/0x440 mm/page_alloc.c:5808
 __alloc_pages_node include/linux/gfp.h:595 [inline]
 alloc_pages_node include/linux/gfp.h:609 [inline]
 alloc_pages include/linux/gfp.h:622 [inline]
 do_anonymous_page mm/memory.c:4069 [inline]
 handle_pte_fault+0xe89/0x2680 mm/memory.c:4909
 __handle_mm_fault mm/memory.c:-1 [inline]
 do_handle_mm_fault+0x1a6d/0x1d50 mm/memory.c:5333
 handle_mm_fault include/linux/mm.h:1847 [inline]
 do_user_addr_fault+0x841/0x1180 arch/x86/mm/fault.c:1418
 handle_page_fault arch/x86/mm/fault.c:1509 [inline]
 exc_page_fault+0x51/0xb0 arch/x86/mm/fault.c:1565
 asm_exc_page_fault+0x27/0x30 arch/x86/include/asm/idtentry.h:606
page last free stack trace:
 reset_page_owner include/linux/page_owner.h:26 [inline]
 free_pages_prepare mm/page_alloc.c:1472 [inline]
 free_pcp_prepare mm/page_alloc.c:1544 [inline]
 free_unref_page_prepare+0x542/0x550 mm/page_alloc.c:3534
 free_unref_page_list+0x134/0x9d0 mm/page_alloc.c:3671
 release_pages+0xfda/0x1030 mm/swap.c:1014
 free_pages_and_swap_cache+0x86/0xa0 mm/swap_state.c:320
 tlb_batch_pages_flush mm/mmu_gather.c:49 [inline]
 tlb_flush_mmu_free mm/mmu_gather.c:240 [inline]
 tlb_flush_mmu+0xd6/0x180 mm/mmu_gather.c:247
 zap_pte_range mm/memory.c:1526 [inline]
 zap_pmd_range mm/memory.c:1575 [inline]
 zap_pud_range mm/memory.c:1604 [inline]
 zap_p4d_range mm/memory.c:1625 [inline]
 unmap_page_range+0x1bcb/0x1d90 mm/memory.c:1646
 unmap_single_vma mm/memory.c:1691 [inline]
 unmap_vmas+0x258/0x360 mm/memory.c:1723
 exit_mmap+0x3e6/0x860 mm/mmap.c:3245
 __mmput+0x93/0x320 kernel/fork.c:1180
 mmput+0x50/0x150 kernel/fork.c:1203
 exit_mm kernel/exit.c:554 [inline]
 do_exit+0x9d2/0x27a0 kernel/exit.c:876
 do_group_exit+0x141/0x310 kernel/exit.c:1003
 get_signal+0x66a/0x1480 kernel/signal.c:2907
 arch_do_signal_or_restart+0xc1/0x10f0 arch/x86/kernel/signal.c:867
 handle_signal_work kernel/entry/common.c:154 [inline]
 exit_to_user_mode_loop+0xa7/0xe0 kernel/entry/common.c:178
 exit_to_user_mode_prepare+0x87/0xd0 kernel/entry/common.c:214

Memory state around the buggy address:
 ffff8881324bdb00: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff8881324bdb80: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
>ffff8881324bdc00: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
                            ^
 ffff8881324bdc80: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff8881324bdd00: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
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