================================================================== BUG: KASAN: use-after-free in ext4_ext_binsearch fs/ext4/extents.c:826 [inline] BUG: KASAN: use-after-free in ext4_find_extent+0xbeb/0xe20 fs/ext4/extents.c:945 Read of size 4 at addr ffff888126258c70 by task kworker/u4:4/380 CPU: 0 PID: 380 Comm: kworker/u4:4 Not tainted syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025 Workqueue: writeback wb_workfn (flush-7:2) Call Trace: __dump_stack+0x21/0x24 lib/dump_stack.c:77 dump_stack_lvl+0x1a7/0x208 lib/dump_stack.c:118 print_address_description+0x7f/0x2c0 mm/kasan/report.c:248 __kasan_report mm/kasan/report.c:435 [inline] kasan_report+0xe2/0x130 mm/kasan/report.c:452 __asan_report_load4_noabort+0x14/0x20 mm/kasan/report_generic.c:308 ext4_ext_binsearch fs/ext4/extents.c:826 [inline] ext4_find_extent+0xbeb/0xe20 fs/ext4/extents.c:945 ext4_ext_map_blocks+0x20b/0x5dd0 fs/ext4/extents.c:4160 ext4_map_blocks+0x985/0x1bd0 fs/ext4/inode.c:674 mpage_map_one_extent fs/ext4/inode.c:2452 [inline] mpage_map_and_submit_extent fs/ext4/inode.c:2505 [inline] ext4_writepages+0x136a/0x2eb0 fs/ext4/inode.c:2873 do_writepages+0x128/0x280 mm/page-writeback.c:2380 __writeback_single_inode+0xd5/0xa20 fs/fs-writeback.c:1470 writeback_sb_inodes+0x8ca/0x1480 fs/fs-writeback.c:1733 wb_writeback+0x403/0xbe0 fs/fs-writeback.c:1908 wb_do_writeback fs/fs-writeback.c:2053 [inline] wb_workfn+0x3ac/0xf30 fs/fs-writeback.c:2094 process_one_work+0x6e1/0xba0 kernel/workqueue.c:2301 worker_thread+0xa6a/0x13c0 kernel/workqueue.c:2447 kthread+0x346/0x3d0 kernel/kthread.c:313 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:298 The buggy address belongs to the page: page:ffffea0004989600 refcount:0 mapcount:0 mapping:0000000000000000 index:0x1 pfn:0x126258 flags: 0x4000000000000000() raw: 4000000000000000 ffffea0004989648 ffffea00049895c8 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 0x100cca(GFP_HIGHUSER_MOVABLE), pid 348, ts 25094094326, free_ts 25253252921 set_page_owner include/linux/page_owner.h:35 [inline] post_alloc_hook mm/page_alloc.c:2456 [inline] prep_new_page+0x179/0x180 mm/page_alloc.c:2462 get_page_from_freelist+0x223b/0x23d0 mm/page_alloc.c:4254 __alloc_pages_nodemask+0x290/0x620 mm/page_alloc.c:5370 __alloc_pages include/linux/gfp.h:544 [inline] __alloc_pages_node include/linux/gfp.h:557 [inline] alloc_pages_node include/linux/gfp.h:571 [inline] alloc_pages include/linux/gfp.h:590 [inline] do_cow_fault mm/memory.c:4418 [inline] do_fault mm/memory.c:4529 [inline] handle_pte_fault+0xf53/0x3750 mm/memory.c:4791 __handle_mm_fault mm/memory.c:4944 [inline] handle_mm_fault+0xf81/0x1710 mm/memory.c:5358 do_user_addr_fault+0x5a8/0xc90 arch/x86/mm/fault.c:1362 handle_page_fault arch/x86/mm/fault.c:1428 [inline] exc_page_fault+0x5a/0xc0 arch/x86/mm/fault.c:1484 asm_exc_page_fault+0x1e/0x30 arch/x86/include/asm/idtentry.h:571 page last free stack trace: reset_page_owner include/linux/page_owner.h:28 [inline] free_pages_prepare mm/page_alloc.c:1349 [inline] free_pcp_prepare mm/page_alloc.c:1421 [inline] free_unref_page_prepare+0x2b7/0x2d0 mm/page_alloc.c:3336 free_unref_page_list+0x129/0x9c0 mm/page_alloc.c:3443 release_pages+0xe52/0xea0 mm/swap.c:1103 free_pages_and_swap_cache+0x86/0xa0 mm/swap_state.c:356 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+0x17e/0x310 mm/mmu_gather.c:326 exit_mmap+0x329/0x590 mm/mmap.c:3387 __mmput+0x93/0x2f0 kernel/fork.c:1153 mmput+0x4e/0x150 kernel/fork.c:1176 exit_mm kernel/exit.c:539 [inline] do_exit+0x9ec/0x2500 kernel/exit.c:859 do_group_exit+0x141/0x310 kernel/exit.c:986 get_signal+0xf7d/0x12e0 kernel/signal.c:2793 arch_do_signal_or_restart+0xe2/0x11d0 arch/x86/kernel/signal.c:805 handle_signal_work kernel/entry/common.c:145 [inline] exit_to_user_mode_loop+0xa2/0xe0 kernel/entry/common.c:169 exit_to_user_mode_prepare+0x76/0xa0 kernel/entry/common.c:199 syscall_exit_to_user_mode+0x1d/0x40 kernel/entry/common.c:274 do_syscall_64+0x3d/0x40 arch/x86/entry/common.c:56 Memory state around the buggy address: ffff888126258b00: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ffff888126258b80: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff >ffff888126258c00: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ^ ffff888126258c80: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ffff888126258d00: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ================================================================== EXT4-fs (loop2): Delayed block allocation failed for inode 15 at logical offset 203 with max blocks 1 with error 117 EXT4-fs (loop2): This should not happen!! Data will be lost EXT4-fs error (device loop2): ext4_ext_split:1144: inode #15: comm kworker/u4:4: eh_entries 26982 != eh_max 25964! EXT4-fs (loop2): Delayed block allocation failed for inode 15 at logical offset 203 with max blocks 1 with error 117 EXT4-fs (loop2): This should not happen!! Data will be lost EXT4-fs error (device loop2): ext4_ext_split:1144: inode #15: comm kworker/u4:4: eh_entries 26982 != eh_max 25964! EXT4-fs error (device loop2): mb_free_blocks:1540: group 0, inode 15: block 353:freeing already freed block (bit 22); block bitmap corrupt. EXT4-fs (loop2): Delayed block allocation failed for inode 15 at logical offset 203 with max blocks 1 with error 117 EXT4-fs (loop2): This should not happen!! Data will be lost EXT4-fs error (device loop2): ext4_ext_split:1144: inode #15: comm kworker/u4:4: eh_entries 26982 != eh_max 25964! EXT4-fs (loop2): Delayed block allocation failed for inode 15 at logical offset 203 with max blocks 1 with error 117 EXT4-fs (loop2): This should not happen!! Data will be lost EXT4-fs (loop2): Delayed block allocation failed for inode 15 at logical offset 203 with max blocks 1 with error 117 EXT4-fs (loop2): This should not happen!! Data will be lost EXT4-fs error (device loop2): ext4_ext_split:1144: inode #15: comm kworker/u4:4: eh_entries 26982 != eh_max 25964!