syzbot

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BUG: KASAN: use-after-free in dx_insert_block+0xd9/0x240 fs/ext4/namei.c:1387
Read of size 157024 at addr ffff888123c72028 by task syz.2.34/437

CPU: 1 PID: 437 Comm: syz.2.34 Not tainted 6.1.134-syzkaller-00016-ga0fa2316cce1 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/19/2025
Call Trace:
 <TASK>
 __dump_stack+0x21/0x24 lib/dump_stack.c:88
 dump_stack_lvl+0xee/0x150 lib/dump_stack.c:106
 print_address_description+0x71/0x210 mm/kasan/report.c:316
 print_report+0x4a/0x60 mm/kasan/report.c:427
 kasan_report+0x122/0x150 mm/kasan/report.c:531
 check_region_inline mm/kasan/generic.c:-1 [inline]
 kasan_check_range+0x280/0x290 mm/kasan/generic.c:189
 memmove+0x2d/0x70 mm/kasan/shadow.c:54
 dx_insert_block+0xd9/0x240 fs/ext4/namei.c:1387
 do_split+0x19ee/0x1d90 fs/ext4/namei.c:2080
 make_indexed_dir+0xe06/0x14a0 fs/ext4/namei.c:2392
 ext4_add_entry+0xb45/0xd70 fs/ext4/namei.c:2504
 __ext4_link+0x4d7/0x770 fs/ext4/namei.c:3522
 ext4_link+0x1de/0x270 fs/ext4/namei.c:3563
 vfs_link+0x64b/0x800 fs/namei.c:4598
 do_linkat+0x1e7/0x730 fs/namei.c:4669
 __do_sys_link fs/namei.c:4703 [inline]
 __se_sys_link fs/namei.c:4701 [inline]
 __x64_sys_link+0x86/0x90 fs/namei.c:4701
 x64_sys_call+0x266/0x9a0 arch/x86/include/generated/asm/syscalls_64.h:87
 do_syscall_x64 arch/x86/entry/common.c:51 [inline]
 do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:81
 entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7faf1f38e969
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:00007faf201bd038 EFLAGS: 00000246 ORIG_RAX: 0000000000000056
RAX: ffffffffffffffda RBX: 00007faf1f5b5fa0 RCX: 00007faf1f38e969
RDX: 0000000000000000 RSI: 0000200000000bc0 RDI: 0000200000001240
RBP: 00007faf1f410ab1 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 0000000000000000 R14: 00007faf1f5b5fa0 R15: 00007ffe13af0148
 </TASK>

The buggy address belongs to the physical page:
page:ffffea00048f1c80 refcount:3 mapcount:1 mapping:ffff88810b9885d0 index:0x1 pfn:0x123c72
memcg:ffff888100334000
aops:def_blk_aops ino:700002
flags: 0x460000000032205e(referenced|uptodate|dirty|lru|workingset|private|mappedtodisk|unevictable|mlocked|zone=1)
raw: 460000000032205e dead000000000100 dead000000000001 ffff88810b9885d0
raw: 0000000000000001 ffff8881156efbd0 0000000300000000 ffff888100334000
page dumped because: kasan: bad access detected
page_owner tracks the page as allocated
page last allocated via order 0, migratetype Unmovable, gfp_mask 0x152c40(GFP_NOFS|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_HARDWALL), pid 390, tgid 390 (udevd), ts 296233338624, free_ts 296215569766
 set_page_owner include/linux/page_owner.h:33 [inline]
 post_alloc_hook+0x1f5/0x210 mm/page_alloc.c:2637
 prep_new_page+0x1c/0x110 mm/page_alloc.c:2644
 get_page_from_freelist+0x2c6e/0x2ce0 mm/page_alloc.c:4539
 __alloc_pages+0x19e/0x3a0 mm/page_alloc.c:5838
 __folio_alloc+0x12/0x40 mm/page_alloc.c:5870
 __folio_alloc_node include/linux/gfp.h:245 [inline]
 folio_alloc include/linux/gfp.h:274 [inline]
 filemap_alloc_folio include/linux/pagemap.h:513 [inline]
 page_cache_ra_unbounded+0x234/0x720 mm/readahead.c:260
 do_page_cache_ra mm/readahead.c:312 [inline]
 force_page_cache_ra mm/readahead.c:343 [inline]
 page_cache_sync_ra+0x3e3/0x490 mm/readahead.c:727
 page_cache_sync_readahead include/linux/pagemap.h:1257 [inline]
 filemap_get_pages mm/filemap.c:2689 [inline]
 filemap_read+0x62d/0x22c0 mm/filemap.c:2784
 blkdev_read_iter+0x41e/0x560 block/fops.c:614
 call_read_iter include/linux/fs.h:2268 [inline]
 new_sync_read fs/read_write.c:389 [inline]
 vfs_read+0x41e/0x8c0 fs/read_write.c:470
 ksys_read+0x140/0x240 fs/read_write.c:613
 __do_sys_read fs/read_write.c:623 [inline]
 __se_sys_read fs/read_write.c:621 [inline]
 __x64_sys_read+0x7b/0x90 fs/read_write.c:621
 x64_sys_call+0x2f/0x9a0 arch/x86/include/generated/asm/syscalls_64.h:1
 do_syscall_x64 arch/x86/entry/common.c:51 [inline]
 do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:81
 entry_SYSCALL_64_after_hwframe+0x68/0xd2
page last free stack trace:
 reset_page_owner include/linux/page_owner.h:26 [inline]
 free_pages_prepare mm/page_alloc.c:1545 [inline]
 free_pcp_prepare mm/page_alloc.c:1619 [inline]
 free_unref_page_prepare+0x742/0x750 mm/page_alloc.c:3581
 free_unref_page+0x8f/0x530 mm/page_alloc.c:3677
 free_the_page mm/page_alloc.c:830 [inline]
 __free_pages+0x67/0x100 mm/page_alloc.c:5927
 __vunmap+0x9af/0xb70 mm/vmalloc.c:2729
 free_work+0x5a/0x80 mm/vmalloc.c:98
 process_one_work+0x71f/0xc40 kernel/workqueue.c:2299
 worker_thread+0xa29/0x11f0 kernel/workqueue.c:2446
 kthread+0x281/0x320 kernel/kthread.c:386
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:295

Memory state around the buggy address:
 ffff888123c74f00: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
 ffff888123c74f80: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
>ffff888123c75000: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                   ^
 ffff888123c75080: fb fc fc fc fc fc fc fc fc fa fb fb fb fb fb fb
 ffff888123c75100: fb fb fb fb fb fb fb fb fb fb fc fc fc fc fc fc
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EXT4-fs error (device loop2): ext4_dx_csum_set:531: inode #2: comm syz.2.34: dir seems corrupt?  Run e2fsck -D.