==================================================================
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 ffff888117a9c018 by task kworker/u4:2/49

CPU: 1 PID: 49 Comm: kworker/u4:2 Not tainted 5.10.238-syzkaller-1007479-gd76d4cd0623a #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/07/2025
Workqueue: writeback wb_workfn (flush-7:2)
Call Trace:
 __dump_stack+0x21/0x24 lib/dump_stack.c:77
 dump_stack_lvl+0x169/0x1d8 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+0x1de/0x5d40 fs/ext4/extents.c:4159
 ext4_map_blocks+0x978/0x1bc0 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+0x11d5/0x2e00 fs/ext4/inode.c:2873
 do_writepages+0x12a/0x270 mm/page-writeback.c:2380
 __writeback_single_inode+0xd5/0xa20 fs/fs-writeback.c:1470
 writeback_sb_inodes+0x860/0x1400 fs/fs-writeback.c:1733
 wb_writeback+0x3e3/0xb90 fs/fs-writeback.c:1908
 wb_do_writeback fs/fs-writeback.c:2053 [inline]
 wb_workfn+0x38f/0xe20 fs/fs-writeback.c:2094
 process_one_work+0x6e1/0xba0 kernel/workqueue.c:2301
 worker_thread+0xa6a/0x13b0 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:ffffea00045ea700 refcount:0 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x117a9c
flags: 0x4000000000000000()
raw: 4000000000000000 ffffea00045ea748 ffffea00045ea348 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 462, ts 53703102738, free_ts 53846936948
 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+0x2235/0x23d0 mm/page_alloc.c:4254
 __alloc_pages_nodemask+0x268/0x5f0 mm/page_alloc.c:5357
 __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]
 __pte_alloc_one include/asm-generic/pgalloc.h:63 [inline]
 pte_alloc_one+0x1f/0xc0 arch/x86/mm/pgtable.c:33
 __pte_alloc+0x24/0x1d0 mm/memory.c:448
 copy_pte_range mm/memory.c:977 [inline]
 copy_pmd_range mm/memory.c:1095 [inline]
 copy_pud_range mm/memory.c:1132 [inline]
 copy_p4d_range mm/memory.c:1156 [inline]
 copy_page_range+0x23ad/0x2870 mm/memory.c:1229
 dup_mmap kernel/fork.c:620 [inline]
 dup_mm kernel/fork.c:1435 [inline]
 copy_mm+0xc63/0x1480 kernel/fork.c:1491
 copy_process+0x1187/0x32c0 kernel/fork.c:2268
 kernel_clone+0x23f/0x940 kernel/fork.c:2650
 __do_sys_clone kernel/fork.c:2776 [inline]
 __se_sys_clone kernel/fork.c:2760 [inline]
 __x64_sys_clone+0x176/0x1d0 kernel/fork.c:2760
 do_syscall_64+0x31/0x40 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x61/0xcb
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+0x12e/0x9b0 mm/page_alloc.c:3443
 release_pages+0xe38/0xe80 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+0x175/0x300 mm/mmu_gather.c:326
 exit_mmap+0x2fc/0x540 mm/mmap.c:3375
 __mmput+0x93/0x2f0 kernel/fork.c:1153
 mmput+0x4e/0x150 kernel/fork.c:1176
 exit_mm kernel/exit.c:539 [inline]
 do_exit+0x986/0x2470 kernel/exit.c:850
 do_group_exit+0x141/0x310 kernel/exit.c:985
 get_signal+0xf7d/0x12e0 kernel/signal.c:2793
 arch_do_signal_or_restart+0xbf/0x10f0 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 kernel/entry/common.c:199 [inline]
 syscall_exit_to_user_mode+0x68/0x90 kernel/entry/common.c:274
 do_syscall_64+0x3d/0x40 arch/x86/entry/common.c:56
 entry_SYSCALL_64_after_hwframe+0x61/0xcb

Memory state around the buggy address:
 ffff888117a9bf00: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff888117a9bf80: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
>ffff888117a9c000: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
                            ^
 ffff888117a9c080: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff888117a9c100: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
==================================================================
EXT4-fs error (device loop2): ext4_map_blocks:740: inode #15: block 126965514593411: comm kworker/u4:2: lblock 84 mapped to illegal pblock 126965514593411 (length 2)
EXT4-fs (loop2): Delayed block allocation failed for inode 15 at logical offset 84 with max blocks 2 with error 117
EXT4-fs (loop2): This should not happen!! Data will be lost

EXT4-fs error (device loop2): ext4_ext_split:1073: inode #15: comm kworker/u4:2: p_ext > EXT_MAX_EXTENT!
EXT4-fs (loop2): Delayed block allocation failed for inode 15 at logical offset 84 with max blocks 2 with error 117
EXT4-fs (loop2): This should not happen!! Data will be lost

EXT4-fs error (device loop2): ext4_ext_split:1073: inode #15: comm kworker/u4:2: p_ext > EXT_MAX_EXTENT!
EXT4-fs (loop2): Delayed block allocation failed for inode 15 at logical offset 84 with max blocks 2 with error 117
EXT4-fs (loop2): This should not happen!! Data will be lost

EXT4-fs error (device loop2): ext4_map_blocks:740: inode #15: block 204206324: comm kworker/u4:2: lblock 84 mapped to illegal pblock 204206324 (length 2)
EXT4-fs (loop2): Delayed block allocation failed for inode 15 at logical offset 84 with max blocks 2 with error 117
EXT4-fs (loop2): This should not happen!! Data will be lost

EXT4-fs error (device loop2): ext4_map_blocks:740: inode #15: block 4294967331: comm kworker/u4:2: lblock 84 mapped to illegal pblock 4294967331 (length 2)
EXT4-fs (loop2): Delayed block allocation failed for inode 15 at logical offset 84 with max blocks 2 with error 117
EXT4-fs (loop2): This should not happen!! Data will be lost