==================================================================
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 ffff888123b5fe5c by task syz.3.19/500

CPU: 0 PID: 500 Comm: syz.3.19 Not tainted 5.10.240-syzkaller-1008073-gad9a98ef27a4 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/07/2025
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_remove_space+0x306/0x4920 fs/ext4/extents.c:2829
 ext4_punch_hole+0x6f8/0xad0 fs/ext4/inode.c:4217
 ext4_fallocate+0x271/0x1a70 fs/ext4/extents.c:4758
 vfs_fallocate+0x4b4/0x590 fs/open.c:310
 ksys_fallocate fs/open.c:333 [inline]
 __do_sys_fallocate fs/open.c:341 [inline]
 __se_sys_fallocate fs/open.c:339 [inline]
 __x64_sys_fallocate+0xc0/0x110 fs/open.c:339
 do_syscall_64+0x31/0x40 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x61/0xcb
RIP: 0033:0x7f9d96bfade9
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:00007f9d9664c038 EFLAGS: 00000246 ORIG_RAX: 000000000000011d
RAX: ffffffffffffffda RBX: 00007f9d96e14080 RCX: 00007f9d96bfade9
RDX: 0000000000000000 RSI: 0000000000000003 RDI: 0000000000000004
RBP: 00007f9d96c7c2a0 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000001a00 R11: 0000000000000246 R12: 0000000000000000
R13: 0000000000000000 R14: 00007f9d96e14080 R15: 00007ffe5bd60f08

The buggy address belongs to the page:
page:ffffea00048ed7c0 refcount:0 mapcount:0 mapping:0000000000000000 index:0x1 pfn:0x123b5f
flags: 0x4000000000000000()
raw: 4000000000000000 ffffea0004930508 ffffea00048ed788 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 0x8100dca(GFP_HIGHUSER_MOVABLE|__GFP_ZERO|0x8000000), pid 496, ts 52959129890, free_ts 52960959790
 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]
 wp_page_copy+0x1d0/0x15d0 mm/memory.c:3166
 do_wp_page+0x9a6/0xc80 mm/memory.c:-1
 handle_pte_fault+0x12ef/0x3750 mm/memory.c:4817
 ___handle_speculative_fault mm/memory.c:5219 [inline]
 __handle_speculative_fault+0xdd6/0x12c0 mm/memory.c:5268
 handle_speculative_fault include/linux/mm.h:1838 [inline]
 do_user_addr_fault+0x7e7/0xc80 arch/x86/mm/fault.c:1285
 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+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
 unmap_region+0x32c/0x380 mm/mmap.c:2807
 __do_munmap+0x63c/0x850 mm/mmap.c:3037
 __vm_munmap mm/mmap.c:3090 [inline]
 __do_sys_munmap mm/mmap.c:3116 [inline]
 __se_sys_munmap+0x127/0x1b0 mm/mmap.c:3112
 __x64_sys_munmap+0x5b/0x70 mm/mmap.c:3112
 do_syscall_64+0x31/0x40 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x61/0xcb

Memory state around the buggy address:
 ffff888123b5fd00: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff888123b5fd80: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
>ffff888123b5fe00: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
                                                    ^
 ffff888123b5fe80: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff888123b5ff00: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
==================================================================
EXT4-fs error (device loop3) in ext4_reserve_inode_write:5933: Corrupt filesystem
EXT4-fs (loop3): Remounting filesystem read-only
EXT4-fs error (device loop3): ext4_dirty_inode:6143: inode #16: comm syz.3.19: mark_inode_dirty error
EXT4-fs error (device loop3): ext4_read_block_bitmap_nowait:476: comm syz.3.19: Invalid block bitmap block 0 in block_group 0
EXT4-fs error (device loop3) in ext4_reserve_inode_write:5933: Corrupt filesystem
EXT4-fs error (device loop3): ext4_punch_hole:4230: inode #16: comm syz.3.19: mark_inode_dirty error