loop0: detected capacity change from 0 to 1024
EXT4-fs: Ignoring removed oldalloc option
EXT4-fs: Ignoring removed orlov option
EXT4-fs (loop0): mounted filesystem without journal. Quota mode: writeback.
==================================================================
BUG: KASAN: use-after-free in ext4_ext_rm_leaf fs/ext4/extents.c:2602 [inline]
BUG: KASAN: use-after-free in ext4_ext_remove_space+0x33ef/0x44c0 fs/ext4/extents.c:2940
Read of size 4 at addr ffff88805a218c18 by task syz.0.26/4432

CPU: 1 PID: 4432 Comm: syz.0.26 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2026
Call Trace:
 <TASK>
 dump_stack_lvl+0x188/0x24e lib/dump_stack.c:106
 print_address_description mm/kasan/report.c:316 [inline]
 print_report+0xa8/0x210 mm/kasan/report.c:420
 kasan_report+0x10b/0x140 mm/kasan/report.c:524
 ext4_ext_rm_leaf fs/ext4/extents.c:2602 [inline]
 ext4_ext_remove_space+0x33ef/0x44c0 fs/ext4/extents.c:2940
 ext4_ext_truncate+0x211/0x370 fs/ext4/extents.c:4470
 ext4_truncate+0xa23/0x1240 fs/ext4/inode.c:4295
 ext4_setattr+0x10cb/0x19f0 fs/ext4/inode.c:5649
 notify_change+0xc74/0xf40 fs/attr.c:499
 do_truncate+0x1ac/0x240 fs/open.c:65
 vfs_truncate+0x262/0x2f0 fs/open.c:111
 do_sys_truncate+0xf2/0x1c0 fs/open.c:134
 do_syscall_x64 arch/x86/entry/common.c:46 [inline]
 do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:76
 entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7f0c6a39c629
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:00007ffde4e0b1e8 EFLAGS: 00000246 ORIG_RAX: 000000000000004c
RAX: ffffffffffffffda RBX: 00007f0c6a615fa0 RCX: 00007f0c6a39c629
RDX: 0000000000000000 RSI: 0000000000000006 RDI: 0000200000000180
RBP: 00007f0c6a432b39 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f0c6a615fac R14: 00007f0c6a615fa0 R15: 00007f0c6a615fa0
 </TASK>

The buggy address belongs to the physical page:
page:ffffea0001688600 refcount:0 mapcount:0 mapping:0000000000000000 index:0x1 pfn:0x5a218
flags: 0xfff00000000000(node=0|zone=1|lastcpupid=0x7ff)
raw: 00fff00000000000 dead000000000100 dead000000000122 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 0x8(__GFP_MOVABLE), pid 1, tgid 1 (swapper/0), ts 23462058731, free_ts 24479877763
 set_page_owner include/linux/page_owner.h:31 [inline]
 post_alloc_hook+0x173/0x1a0 mm/page_alloc.c:2559
 split_map_pages+0x280/0x4d0 mm/compaction.c:97
 isolate_freepages_range+0x3e5/0x440 mm/compaction.c:735
 alloc_contig_range+0x5d4/0x890 mm/page_alloc.c:9486
 __alloc_contig_pages mm/page_alloc.c:9509 [inline]
 alloc_contig_pages+0x396/0x490 mm/page_alloc.c:9589
 debug_vm_pgtable_alloc_huge_page+0xbf/0x10f mm/debug_vm_pgtable.c:1103
 init_args+0xb94/0xeda mm/debug_vm_pgtable.c:1226
 debug_vm_pgtable+0x56/0x38e mm/debug_vm_pgtable.c:1264
 do_one_initcall+0x26a/0x840 init/main.c:1310
 do_initcall_level+0x137/0x1e4 init/main.c:1383
 do_initcalls+0x4b/0x8a init/main.c:1399
 kernel_init_freeable+0x415/0x5be init/main.c:1638
 kernel_init+0x19/0x1b0 init/main.c:1526
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:295
page last free stack trace:
 reset_page_owner include/linux/page_owner.h:24 [inline]
 free_pages_prepare mm/page_alloc.c:1486 [inline]
 free_pcp_prepare mm/page_alloc.c:1536 [inline]
 free_unref_page_prepare+0x8b4/0x9a0 mm/page_alloc.c:3413
 free_unref_page+0x2e/0x3f0 mm/page_alloc.c:3508
 free_contig_range+0x9d/0x150 mm/page_alloc.c:9611
 destroy_args+0xf0/0xa0a mm/debug_vm_pgtable.c:1031
 debug_vm_pgtable+0x33c/0x38e mm/debug_vm_pgtable.c:1359
 do_one_initcall+0x26a/0x840 init/main.c:1310
 do_initcall_level+0x137/0x1e4 init/main.c:1383
 do_initcalls+0x4b/0x8a init/main.c:1399
 kernel_init_freeable+0x415/0x5be init/main.c:1638
 kernel_init+0x19/0x1b0 init/main.c:1526
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:295

Memory state around the buggy address:
 ffff88805a218b00: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff88805a218b80: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
>ffff88805a218c00: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
                            ^
 ffff88805a218c80: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff88805a218d00: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
==================================================================