==================================================================
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 ffff88812dc5db2c by task syz.2.16/469

CPU: 1 PID: 469 Comm: syz.2.16 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 08/18/2025
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: 0033:0x7f6924f56de9
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:00007f69249c9038 EFLAGS: 00000246 ORIG_RAX: 000000000000011d
RAX: ffffffffffffffda RBX: 00007f692516ffa0 RCX: 00007f6924f56de9
RDX: 0000000000000000 RSI: 0000000000000003 RDI: 0000000000000005
RBP: 00007f6924fd82a0 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000001a00 R11: 0000000000000246 R12: 0000000000000000
R13: 0000000000000000 R14: 00007f692516ffa0 R15: 00007ffc12c15058

The buggy address belongs to the page:
page:ffffea0004b71740 refcount:0 mapcount:0 mapping:0000000000000000 index:0x1 pfn:0x12dc5d
flags: 0x4000000000000000()
raw: 4000000000000000 ffffea0004b72a88 ffffea0004b71708 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 469, ts 47580192135, free_ts 47581190885
 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: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]
 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:1849 [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:2811
 __do_munmap+0x63c/0x850 mm/mmap.c:3041
 __vm_munmap mm/mmap.c:3094 [inline]
 __do_sys_munmap mm/mmap.c:3120 [inline]
 __se_sys_munmap+0x127/0x1b0 mm/mmap.c:3116
 __x64_sys_munmap+0x5b/0x70 mm/mmap.c:3116
 do_syscall_64+0x31/0x40 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x61/0xcb

Memory state around the buggy address:
 ffff88812dc5da00: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff88812dc5da80: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
>ffff88812dc5db00: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
                                  ^
 ffff88812dc5db80: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff88812dc5dc00: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
==================================================================
EXT4-fs error (device loop2): ext4_free_blocks:5685: comm syz.2.16: Freeing blocks not in datazone - block = 0, count = 1
EXT4-fs error (device loop2): __ext4_get_inode_loc:4438: comm syz.2.16: Invalid inode table block 0 in block_group 0
EXT4-fs error (device loop2) in ext4_reserve_inode_write:5933: Corrupt filesystem
EXT4-fs error (device loop2): ext4_punch_hole:4230: inode #16: comm syz.2.16: mark_inode_dirty error