EXT4-fs error (device loop5): ext4_free_blocks:5685: comm syz.5.20: Freeing blocks not in datazone - block = 81305331339894, count = 17012
==================================================================
BUG: KASAN: use-after-free in ext4_ext_store_pblock fs/ext4/ext4_extents.h:255 [inline]
BUG: KASAN: use-after-free in ext4_ext_rm_leaf fs/ext4/extents.c:2692 [inline]
BUG: KASAN: use-after-free in ext4_ext_remove_space+0x2bfd/0x4920 fs/ext4/extents.c:2934
Write of size 4 at addr ffff8881313c199c by task syz.5.20/517

CPU: 0 PID: 517 Comm: syz.5.20 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_store4_noabort+0x17/0x20 mm/kasan/report_generic.c:313
 ext4_ext_store_pblock fs/ext4/ext4_extents.h:255 [inline]
 ext4_ext_rm_leaf fs/ext4/extents.c:2692 [inline]
 ext4_ext_remove_space+0x2bfd/0x4920 fs/ext4/extents.c:2934
 ext4_ext_truncate+0x169/0x1f0 fs/ext4/extents.c:4467
 ext4_truncate+0xaea/0x1290 fs/ext4/inode.c:4367
 ext4_truncate_failed_write fs/ext4/truncate.h:20 [inline]
 ext4_write_begin+0xd78/0x15a0 fs/ext4/inode.c:1276
 ext4_da_write_begin+0x455/0xe80 fs/ext4/inode.c:3033
 generic_perform_write+0x2be/0x510 mm/filemap.c:3509
 ext4_buffered_write_iter+0x4b8/0x640 fs/ext4/file.c:271
 ext4_file_write_iter+0x536/0x1980 fs/ext4/file.c:-1
 call_write_iter include/linux/fs.h:2066 [inline]
 new_sync_write fs/read_write.c:518 [inline]
 vfs_write+0x725/0xd60 fs/read_write.c:605
 ksys_write+0x140/0x240 fs/read_write.c:658
 __do_sys_write fs/read_write.c:670 [inline]
 __se_sys_write fs/read_write.c:667 [inline]
 __x64_sys_write+0x7b/0x90 fs/read_write.c:667
 do_syscall_64+0x31/0x40 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x61/0xcb
RIP: 0033:0x7f28df985169
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:00007f28df3d6038 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 00007f28dfb9e080 RCX: 00007f28df985169
RDX: 0000000000040010 RSI: 0000400000000180 RDI: 0000000000000006
RBP: 00007f28dfa062a0 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 0000000000000000 R14: 00007f28dfb9e080 R15: 00007fff170fa408

The buggy address belongs to the page:
page:ffffea0004c4f040 refcount:0 mapcount:0 mapping:0000000000000000 index:0x1 pfn:0x1313c1
flags: 0x4000000000000000()
raw: 4000000000000000 ffffea0004c4f088 ffffea0004c4f008 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 515, ts 51082259219, free_ts 51175257733
 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]
 do_anonymous_page mm/memory.c:3963 [inline]
 handle_pte_fault+0x1719/0x3750 mm/memory.c:4786
 __handle_mm_fault mm/memory.c:4944 [inline]
 handle_mm_fault+0xf3f/0x16a0 mm/memory.c:5358
 do_user_addr_fault+0x5a2/0xc80 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+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:3387
 __mmput+0x93/0x2f0 kernel/fork.c:1153
 mmput+0x4e/0x150 kernel/fork.c:1176
 exit_mm kernel/exit.c:539 [inline]
 do_exit+0x9ae/0x2480 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+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+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:
 ffff8881313c1880: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff8881313c1900: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
>ffff8881313c1980: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
                            ^
 ffff8881313c1a00: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff8881313c1a80: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
==================================================================
EXT4-fs error (device loop5): ext4_free_blocks:5685: comm syz.5.20: Freeing blocks not in datazone - block = 241364661970887, count = 11256
EXT4-fs error (device loop5): ext4_free_blocks:5685: comm syz.5.20: Freeing blocks not in datazone - block = 48605256792457, count = 29602
EXT4-fs error (device loop5): ext4_free_blocks:5685: comm syz.5.20: Freeing blocks not in datazone - block = 203054344451624, count = 21868
EXT4-fs error (device loop5): ext4_free_blocks:5685: comm syz.5.20: Freeing blocks not in datazone - block = 134202109153992, count = 12062
EXT4-fs error (device loop5): ext4_free_blocks:5685: comm syz.5.20: Freeing blocks not in datazone - block = 96400301720015, count = 22909
EXT4-fs error (device loop5): ext4_free_blocks:5685: comm syz.5.20: Freeing blocks not in datazone - block = 249626416810403, count = 11755
EXT4-fs error (device loop5): ext4_free_blocks:5685: comm syz.5.20: Freeing blocks not in datazone - block = 157095320840886, count = 13653
EXT4-fs error (device loop5): ext4_free_blocks:5685: comm syz.5.20: Freeing blocks not in datazone - block = 89127299342976, count = 9330
EXT4-fs error (device loop5): ext4_free_blocks:5685: comm syz.5.20: Freeing blocks not in datazone - block = 246026673647751, count = 10953