syzbot

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BUG: KASAN: use-after-free in ext4_ext_rm_leaf fs/ext4/extents.c:2627 [inline]
BUG: KASAN: use-after-free in ext4_ext_remove_space+0x31a5/0x4260 fs/ext4/extents.c:2965
Read of size 4 at addr ffff888048296c18 by task syz-executor/6133

CPU: 0 UID: 0 PID: 6133 Comm: syz-executor Not tainted syzkaller #0 PREEMPT_{RT,(full)} [  153.247766][ T6133] CPU: 0 UID: 0 PID: 6133 Comm: syz-executor Not tainted syzkaller #0 PREEMPT_{RT,(full)} 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025
Call Trace:
 <TASK>
 dump_stack_lvl+0xe8/0x150 lib/dump_stack.c:120
 print_address_description mm/kasan/report.c:378 [inline]
 print_report+0xca/0x240 mm/kasan/report.c:482
 kasan_report+0x118/0x150 mm/kasan/report.c:595
 ext4_ext_rm_leaf fs/ext4/extents.c:2627 [inline]
 ext4_ext_remove_space+0x31a5/0x4260 fs/ext4/extents.c:2965
 ext4_ext_truncate+0x17e/0x300 fs/ext4/extents.c:4484
 ext4_truncate+0xb3f/0x1300 fs/ext4/inode.c:4612
 ext4_evict_inode+0x85e/0xe60 fs/ext4/inode.c:260
 evict+0x5f4/0xae0 fs/inode.c:837
 do_unlinkat+0x340/0x570 fs/namei.c:5443
 __do_sys_unlink fs/namei.c:5474 [inline]
 __se_sys_unlink fs/namei.c:5472 [inline]
 __x64_sys_unlink+0x47/0x50 fs/namei.c:5472
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xec/0xf80 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f76aeb7ecf7
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:00007ffd301bc468 EFLAGS: 00000206 ORIG_RAX: 0000000000000057
RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00007f76aeb7ecf7
RDX: 00007ffd301bc490 RSI: 00007ffd301bc520 RDI: 00007ffd301bc520
RBP: 00007ffd301bc520 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000100 R11: 0000000000000206 R12: 00007ffd301bd610
R13: 00007f76aec03d7d R14: 0000000000025561 R15: 00007ffd301be6e0
 </TASK>

The buggy address belongs to the physical page:
page: refcount:0 mapcount:0 mapping:0000000000000000 index:0x7f3e95e76 pfn:0x48296
flags: 0x80000000000000(node=0|zone=1)
raw: 0080000000000000 dead000000000100 dead000000000122 0000000000000000
raw: 00000007f3e95e76 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 0x140dca(GFP_HIGHUSER_MOVABLE|__GFP_ZERO|__GFP_COMP), pid 5809, tgid 5809 (syz-executor), ts 102889688362, free_ts 109393720478
 set_page_owner include/linux/page_owner.h:32 [inline]
 post_alloc_hook+0x234/0x290 mm/page_alloc.c:1857
 prep_new_page mm/page_alloc.c:1865 [inline]
 get_page_from_freelist+0x28c0/0x2960 mm/page_alloc.c:3915
 __alloc_frozen_pages_noprof+0x181/0x370 mm/page_alloc.c:5210
 alloc_pages_mpol+0xd1/0x380 mm/mempolicy.c:2486
 folio_alloc_mpol_noprof mm/mempolicy.c:2505 [inline]
 vma_alloc_folio_noprof+0xe4/0x280 mm/mempolicy.c:2540
 folio_prealloc+0x30/0x180 mm/memory.c:-1
 alloc_anon_folio mm/memory.c:5165 [inline]
 do_anonymous_page mm/memory.c:5222 [inline]
 do_pte_missing+0x86a/0x27a0 mm/memory.c:4399
 handle_pte_fault mm/memory.c:6273 [inline]
 __handle_mm_fault mm/memory.c:6411 [inline]
 handle_mm_fault+0xcc1/0x1330 mm/memory.c:6580
 do_user_addr_fault+0xa7c/0x1380 arch/x86/mm/fault.c:1336
 handle_page_fault arch/x86/mm/fault.c:1476 [inline]
 exc_page_fault+0x71/0xd0 arch/x86/mm/fault.c:1532
 asm_exc_page_fault+0x26/0x30 arch/x86/include/asm/idtentry.h:618
page last free pid 5809 tgid 5809 stack trace:
 reset_page_owner include/linux/page_owner.h:25 [inline]
 free_pages_prepare mm/page_alloc.c:1406 [inline]
 free_unref_folios+0xc28/0x1810 mm/page_alloc.c:3000
 folios_put_refs+0x569/0x670 mm/swap.c:1002
 free_pages_and_swap_cache+0x277/0x520 mm/swap_state.c:355
 __tlb_batch_free_encoded_pages mm/mmu_gather.c:136 [inline]
 tlb_batch_pages_flush mm/mmu_gather.c:149 [inline]
 tlb_flush_mmu_free mm/mmu_gather.c:397 [inline]
 tlb_flush_mmu+0x3a0/0x680 mm/mmu_gather.c:404
 tlb_finish_mmu+0xc3/0x1d0 mm/mmu_gather.c:497
 vms_clear_ptes+0x42b/0x530 mm/vma.c:1238
 vms_complete_munmap_vmas+0x206/0x8a0 mm/vma.c:1280
 do_vmi_align_munmap+0x372/0x450 mm/vma.c:1539
 do_vmi_munmap+0x253/0x2e0 mm/vma.c:1587
 __vm_munmap+0x207/0x380 mm/vma.c:3203
 __do_sys_munmap mm/mmap.c:1077 [inline]
 __se_sys_munmap mm/mmap.c:1074 [inline]
 __x64_sys_munmap+0x60/0x70 mm/mmap.c:1074
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xec/0xf80 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

Memory state around the buggy address:
 ffff888048296b00: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff888048296b80: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
>ffff888048296c00: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
                            ^
 ffff888048296c80: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff888048296d00: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
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