==================================================================
BUG: KASAN: use-after-free in ext4_ext_binsearch fs/ext4/extents.c:827 [inline]
BUG: KASAN: use-after-free in ext4_find_extent+0xbfb/0xe30 fs/ext4/extents.c:946
Read of size 4 at addr ffff888130502ccc by task syz.2.17/480

CPU: 1 PID: 480 Comm: syz.2.17 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/16/2026
Call Trace:
 <TASK>
 __dump_stack+0x21/0x30 lib/dump_stack.c:88
 dump_stack_lvl+0x110/0x170 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+0x10f/0x150 mm/kasan/report.c:444
 __asan_report_load4_noabort+0x14/0x20 mm/kasan/report_generic.c:308
 ext4_ext_binsearch fs/ext4/extents.c:827 [inline]
 ext4_find_extent+0xbfb/0xe30 fs/ext4/extents.c:946
 ext4_ext_remove_space+0x2bd/0x3e60 fs/ext4/extents.c:2849
 ext4_punch_hole+0x7a9/0xbf0 fs/ext4/inode.c:4139
 ext4_fallocate+0x2ae/0x1de0 fs/ext4/extents.c:4796
 vfs_fallocate+0x4b9/0x590 fs/open.c:309
 ksys_fallocate fs/open.c:332 [inline]
 __do_sys_fallocate fs/open.c:340 [inline]
 __se_sys_fallocate fs/open.c:338 [inline]
 __x64_sys_fallocate+0xc0/0x110 fs/open.c:338
 x64_sys_call+0x7ec/0x9a0 arch/x86/include/generated/asm/syscalls_64.h:286
 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: 0033:0x7fe37222a339
Code: ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 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 e8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007fe37208f028 EFLAGS: 00000246 ORIG_RAX: 000000000000011d
RAX: ffffffffffffffda RBX: 00007fe372465fa0 RCX: 00007fe37222a339
RDX: 0000000000000000 RSI: 0000000000000003 RDI: 0000000000000005
RBP: 00007fe3722bdd68 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000001a00 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fe372466038 R14: 00007fe372465fa0 R15: 00007ffef4a41b58
 </TASK>

The buggy address belongs to the page:
page:ffffea0004c14080 refcount:0 mapcount:0 mapping:0000000000000000 index:0x1 pfn:0x130502
flags: 0x4000000000000000(zone=1)
raw: 4000000000000000 ffffea0004c140c8 ffffea0004c14048 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 0x100dca(GFP_HIGHUSER_MOVABLE|__GFP_ZERO), pid 418, ts 35460134099, free_ts 35460697834
 set_page_owner include/linux/page_owner.h:33 [inline]
 post_alloc_hook+0x192/0x1b0 mm/page_alloc.c:2607
 prep_new_page+0x1c/0x110 mm/page_alloc.c:2613
 get_page_from_freelist+0x2c3a/0x2cd0 mm/page_alloc.c:4487
 __alloc_pages+0x1a2/0x460 mm/page_alloc.c:5824
 __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]
 do_anonymous_page mm/memory.c:4072 [inline]
 handle_pte_fault+0xee5/0x2770 mm/memory.c:4921
 __handle_mm_fault mm/memory.c:-1 [inline]
 do_handle_mm_fault+0x1b3b/0x1e30 mm/memory.c:5345
 handle_mm_fault include/linux/mm.h:1847 [inline]
 do_user_addr_fault+0x808/0x11c0 arch/x86/mm/fault.c:1416
 handle_page_fault arch/x86/mm/fault.c:1507 [inline]
 exc_page_fault+0x51/0xb0 arch/x86/mm/fault.c:1560
 asm_exc_page_fault+0x27/0x30 arch/x86/include/asm/idtentry.h:606
page last free stack trace:
 reset_page_owner include/linux/page_owner.h:26 [inline]
 free_pages_prepare mm/page_alloc.c:1474 [inline]
 free_pcp_prepare mm/page_alloc.c:1546 [inline]
 free_unref_page_prepare+0x5fa/0x600 mm/page_alloc.c:3536
 free_unref_page_list+0x138/0x9e0 mm/page_alloc.c:3673
 release_pages+0x1264/0x12c0 mm/swap.c:1015
 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+0x17e/0x310 mm/mmu_gather.c:338
 unmap_region+0x344/0x3b0 mm/mmap.c:2692
 __do_munmap+0xa99/0x1090 mm/mmap.c:2925
 __vm_munmap+0x14e/0x280 mm/mmap.c:2978
 __do_sys_munmap mm/mmap.c:3004 [inline]
 __se_sys_munmap mm/mmap.c:3000 [inline]
 __x64_sys_munmap+0x6b/0x80 mm/mmap.c:3000
 x64_sys_call+0xc9/0x9a0 arch/x86/include/generated/asm/syscalls_64.h:12
 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

Memory state around the buggy address:
 ffff888130502b80: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff888130502c00: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
>ffff888130502c80: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
                                              ^
 ffff888130502d00: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff888130502d80: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
==================================================================
------------[ cut here ]------------
kernel BUG at fs/ext4/extents.c:3204!
invalid opcode: 0000 [#1] PREEMPT SMP KASAN
CPU: 1 PID: 480 Comm: syz.2.17 Tainted: G    B             syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/16/2026
RIP: 0010:ext4_split_extent_at+0xe3f/0xe60 fs/ext4/extents.c:3204
Code: fc ff ff 89 d9 80 e1 07 fe c1 38 c1 0f 8c 19 fc ff ff 48 89 df 49 89 d4 e8 5e d4 d2 ff 4c 89 e2 e9 06 fc ff ff e8 f1 53 93 ff <0f> 0b e8 ea 53 93 ff 0f 0b e8 e3 53 93 ff 0f 0b e8 dc 53 93 ff 0f
RSP: 0018:ffffc90000aa7920 EFLAGS: 00010293
RAX: ffffffff81d6876f RBX: 1ffff110260a0d30 RCX: ffff888119b76400
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000001
RBP: ffffc90000aa7a90 R08: 0000000000000000 R09: 0000000050000028
R10: dffffc0000000000 R11: fffffbfff0e1904c R12: ffff888119fe1f00
R13: dffffc0000000000 R14: 0000000000000000 R15: 0000000000000000
FS:  00007fe37208f6c0(0000) GS:ffff8881f7100000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007fae134a2000 CR3: 000000012c78c000 CR4: 00000000003506a0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 <TASK>
 ext4_force_split_extent_at fs/ext4/extents.c:319 [inline]
 ext4_ext_remove_space+0x618/0x3e60 fs/ext4/extents.c:2895
 ext4_punch_hole+0x7a9/0xbf0 fs/ext4/inode.c:4139
 ext4_fallocate+0x2ae/0x1de0 fs/ext4/extents.c:4796
 vfs_fallocate+0x4b9/0x590 fs/open.c:309
 ksys_fallocate fs/open.c:332 [inline]
 __do_sys_fallocate fs/open.c:340 [inline]
 __se_sys_fallocate fs/open.c:338 [inline]
 __x64_sys_fallocate+0xc0/0x110 fs/open.c:338
 x64_sys_call+0x7ec/0x9a0 arch/x86/include/generated/asm/syscalls_64.h:286
 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: 0033:0x7fe37222a339
Code: ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 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 e8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007fe37208f028 EFLAGS: 00000246 ORIG_RAX: 000000000000011d
RAX: ffffffffffffffda RBX: 00007fe372465fa0 RCX: 00007fe37222a339
RDX: 0000000000000000 RSI: 0000000000000003 RDI: 0000000000000005
RBP: 00007fe3722bdd68 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000001a00 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fe372466038 R14: 00007fe372465fa0 R15: 00007ffef4a41b58
 </TASK>
Modules linked in:
---[ end trace 18ba30f4db19f07b ]---
RIP: 0010:ext4_split_extent_at+0xe3f/0xe60 fs/ext4/extents.c:3204
Code: fc ff ff 89 d9 80 e1 07 fe c1 38 c1 0f 8c 19 fc ff ff 48 89 df 49 89 d4 e8 5e d4 d2 ff 4c 89 e2 e9 06 fc ff ff e8 f1 53 93 ff <0f> 0b e8 ea 53 93 ff 0f 0b e8 e3 53 93 ff 0f 0b e8 dc 53 93 ff 0f
RSP: 0018:ffffc90000aa7920 EFLAGS: 00010293
RAX: ffffffff81d6876f RBX: 1ffff110260a0d30 RCX: ffff888119b76400
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000001
RBP: ffffc90000aa7a90 R08: 0000000000000000 R09: 0000000050000028
R10: dffffc0000000000 R11: fffffbfff0e1904c R12: ffff888119fe1f00
R13: dffffc0000000000 R14: 0000000000000000 R15: 0000000000000000
FS:  00007fe37208f6c0(0000) GS:ffff8881f7000000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007fe372277a80 CR3: 000000012c78c000 CR4: 00000000003506b0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400