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BUG: KASAN: use-after-free in ext4_ext_binsearch_idx fs/ext4/extents.c:759 [inline]
BUG: KASAN: use-after-free in ext4_find_extent+0x794/0xe20 fs/ext4/extents.c:924
Read of size 4 at addr ffff8881426bc274 by task syz.6.898/3965

CPU: 1 PID: 3965 Comm: syz.6.898 Tainted: G        W         syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025
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_idx fs/ext4/extents.c:759 [inline]
 ext4_find_extent+0x794/0xe20 fs/ext4/extents.c:924
 ext4_ext_map_blocks+0x1db/0x6270 fs/ext4/extents.c:4166
 ext4_map_blocks+0x97b/0x1b20 fs/ext4/inode.c:674
 mpage_map_one_extent fs/ext4/inode.c:2421 [inline]
 mpage_map_and_submit_extent fs/ext4/inode.c:2474 [inline]
 ext4_writepages+0x11e7/0x2f90 fs/ext4/inode.c:2842
 do_writepages+0x48a/0x6c0 mm/page-writeback.c:2388
 filemap_fdatawrite_wbc+0x1f4/0x250 mm/filemap.c:409
 __filemap_fdatawrite_range mm/filemap.c:442 [inline]
 file_write_and_wait_range+0x129/0x1e0 mm/filemap.c:819
 ext4_sync_file+0x1a9/0xa10 fs/ext4/fsync.c:151
 vfs_fsync_range+0x190/0x1a0 fs/sync.c:188
 generic_write_sync include/linux/fs.h:3038 [inline]
 ext4_buffered_write_iter+0x5d0/0x670 fs/ext4/file.c:277
 ext4_file_write_iter+0x18c/0x1550 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: 0033:0x7f87d86a8749
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:00007f87d70ef038 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 00007f87d88ff090 RCX: 00007f87d86a8749
RDX: 00000000fffffed6 RSI: 0000200000001700 RDI: 0000000000000004
RBP: 00007f87d872cf91 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f87d88ff128 R14: 00007f87d88ff090 R15: 00007ffc6d32aef8
 </TASK>

The buggy address belongs to the page:
page:ffffea000509af00 refcount:0 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x1426bc
flags: 0x4000000000000000(zone=1)
raw: 4000000000000000 dead000000000100 dead000000000122 0000000000000000
raw: 0000000000000000 0000000000000000 00000000ffffffff 0000000000000000
page dumped because: kasan: bad access detected
page_owner tracks the page as freed
page last allocated via order 0, migratetype Unmovable, gfp_mask 0x500dc0(GFP_USER|__GFP_ZERO|__GFP_ACCOUNT), pid 2993, ts 155916341835, free_ts 156799273319
 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]
 __pte_alloc_one include/asm-generic/pgalloc.h:63 [inline]
 pte_alloc_one+0x70/0x180 arch/x86/mm/pgtable.c:33
 __pte_alloc+0x75/0x290 mm/memory.c:502
 copy_pte_range mm/memory.c:1096 [inline]
 copy_pmd_range mm/memory.c:1231 [inline]
 copy_pud_range mm/memory.c:1268 [inline]
 copy_p4d_range mm/memory.c:1292 [inline]
 copy_page_range+0x2348/0x2890 mm/memory.c:1365
 dup_mmap kernel/fork.c:660 [inline]
 dup_mm kernel/fork.c:1522 [inline]
 copy_mm+0xbe2/0x13a0 kernel/fork.c:1574
 copy_process+0x115c/0x3210 kernel/fork.c:2348
 kernel_clone+0x23f/0x940 kernel/fork.c:2737
 __do_sys_clone kernel/fork.c:2863 [inline]
 __se_sys_clone kernel/fork.c:2847 [inline]
 __x64_sys_clone+0x176/0x1d0 kernel/fork.c:2847
 x64_sys_call+0x41f/0x9a0 arch/x86/include/generated/asm/syscalls_64.h:57
 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
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 mm/mmu_gather.c:247 [inline]
 tlb_finish_mmu+0x175/0x300 mm/mmu_gather.c:338
 exit_mmap+0x40f/0x860 mm/mmap.c:3248
 __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
 __syscall_exit_to_user_mode_work kernel/entry/common.c:296 [inline]
 syscall_exit_to_user_mode+0x1a/0x30 kernel/entry/common.c:307
 do_syscall_64+0x58/0xa0 arch/x86/entry/common.c:86

Memory state around the buggy address:
 ffff8881426bc100: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff8881426bc180: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
>ffff8881426bc200: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
                                                             ^
 ffff8881426bc280: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff8881426bc300: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
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