[syzbot] KASAN: use-after-free Read in nilfs_update_inode

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 493ffd6605b2 Merge tag 'ucount-rlimits-cleanups-for-v5.19'..
git tree: upstream
console+strace: https://syzkaller.appspot.com/x/log.txt?x=1241e73a880000
kernel config: https://syzkaller.appspot.com/x/.config?x=d19f5d16783f901
dashboard link: https://syzkaller.appspot.com/bug?extid=ddb45ee60a8ea1b7a21f
compiler: Debian clang version 13.0.1-++20220126092033+75e33f71c2da-1~exp1~20220126212112.63, GNU ld (GNU Binutils for Debian) 2.35.2
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=11cd6daa880000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=16594b8a880000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/f1ff6481e26f/disk-493ffd66.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/101bd3c7ae47/vmlinux-493ffd66.xz
mounted in repro: https://storage.googleapis.com/syzbot-assets/9097ed9eaf36/mount_0.gz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+ddb45e...@syzkaller.appspotmail.com

syz-executor141: attempt to access beyond end of device
loop0: rw=0, sector=15744656570680999970, nr_sectors = 2 limit=2048
syz-executor141: attempt to access beyond end of device
loop0: rw=0, sector=15744656570680999970, nr_sectors = 2 limit=2048
==================================================================
BUG: KASAN: use-after-free in nilfs_update_inode+0x72/0x1c0 fs/nilfs2/inode.c:788
Read of size 8 at addr ffff88801f816230 by task syz-executor141/3606

CPU: 1 PID: 3606 Comm: syz-executor141 Not tainted 6.0.0-syzkaller-09423-g493ffd6605b2 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/22/2022
Call Trace:
<TASK>
__dump_stack lib/dump_stack.c:88 [inline]
dump_stack_lvl+0x1b1/0x28e lib/dump_stack.c:106
print_address_description+0x65/0x4b0 mm/kasan/report.c:317
print_report+0x108/0x1f0 mm/kasan/report.c:433
kasan_report+0xc3/0xf0 mm/kasan/report.c:495
nilfs_update_inode+0x72/0x1c0 fs/nilfs2/inode.c:788
__nilfs_mark_inode_dirty+0xc2/0x250 fs/nilfs2/inode.c:1079
nilfs_mark_inode_dirty fs/nilfs2/nilfs.h:288 [inline]
nilfs_mkdir+0x24e/0x320 fs/nilfs2/namei.c:255
vfs_mkdir+0x3b3/0x590 fs/namei.c:4013
do_mkdirat+0x279/0x550 fs/namei.c:4038
__do_sys_mkdirat fs/namei.c:4053 [inline]
__se_sys_mkdirat fs/namei.c:4051 [inline]
__x64_sys_mkdirat+0x85/0x90 fs/namei.c:4051
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x3d/0xb0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x63/0xcd
RIP: 0033:0x7f5c14d482e9
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 c0 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007ffdc679fd08 EFLAGS: 00000246 ORIG_RAX: 0000000000000102
RAX: ffffffffffffffda RBX: 000000000000001e RCX: 00007f5c14d482e9
RDX: 0000000000000000 RSI: 0000000020000000 RDI: 0000000000000003
RBP: 00007f5c14d07ab0 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00007f5c14d07b40
R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000
</TASK>

Allocated by task 3606:
kasan_save_stack mm/kasan/common.c:38 [inline]
kasan_set_track mm/kasan/common.c:45 [inline]
set_alloc_info mm/kasan/common.c:437 [inline]
____kasan_kmalloc+0xcd/0x100 mm/kasan/common.c:516
kasan_kmalloc include/linux/kasan.h:234 [inline]
kmem_cache_alloc_trace+0x97/0x310 mm/slub.c:3289
kmalloc include/linux/slab.h:600 [inline]
kzalloc include/linux/slab.h:733 [inline]
nilfs_find_or_create_root+0x142/0x4f0 fs/nilfs2/the_nilfs.c:747
nilfs_attach_checkpoint+0xcd/0x4a0 fs/nilfs2/super.c:519
nilfs_fill_super+0x2e8/0x5d0 fs/nilfs2/super.c:1064
nilfs_mount+0x613/0x9b0 fs/nilfs2/super.c:1317
legacy_get_tree+0xea/0x180 fs/fs_context.c:610
vfs_get_tree+0x88/0x270 fs/super.c:1530
do_new_mount+0x289/0xad0 fs/namespace.c:3040
do_mount fs/namespace.c:3383 [inline]
__do_sys_mount fs/namespace.c:3591 [inline]
__se_sys_mount+0x2d3/0x3c0 fs/namespace.c:3568
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x3d/0xb0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x63/0xcd

Freed by task 3606:
kasan_save_stack mm/kasan/common.c:38 [inline]
kasan_set_track+0x3d/0x60 mm/kasan/common.c:45
kasan_set_free_info+0x1f/0x40 mm/kasan/generic.c:370
____kasan_slab_free+0xd8/0x120 mm/kasan/common.c:367
kasan_slab_free include/linux/kasan.h:200 [inline]
slab_free_hook mm/slub.c:1759 [inline]
slab_free_freelist_hook+0x12e/0x1a0 mm/slub.c:1785
slab_free mm/slub.c:3539 [inline]
kfree+0xda/0x210 mm/slub.c:4567
nilfs_evict_inode+0x253/0x3d0 fs/nilfs2/inode.c:924
evict+0x2a4/0x620 fs/inode.c:664
nilfs_new_inode+0x6b8/0x8a0
nilfs_mkdir+0xfc/0x320 fs/nilfs2/namei.c:218
vfs_mkdir+0x3b3/0x590 fs/namei.c:4013
do_mkdirat+0x279/0x550 fs/namei.c:4038
__do_sys_mkdirat fs/namei.c:4053 [inline]
__se_sys_mkdirat fs/namei.c:4051 [inline]
__x64_sys_mkdirat+0x85/0x90 fs/namei.c:4051
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x3d/0xb0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x63/0xcd

The buggy address belongs to the object at ffff88801f816200
which belongs to the cache kmalloc-256 of size 256
The buggy address is located 48 bytes inside of
256-byte region [ffff88801f816200, ffff88801f816300)

The buggy address belongs to the physical page:
page:ffffea00007e0580 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x1f816
head:ffffea00007e0580 order:1 compound_mapcount:0 compound_pincount:0
flags: 0xfff00000010200(slab|head|node=0|zone=1|lastcpupid=0x7ff)
raw: 00fff00000010200 ffffea00004b9200 dead000000000004 ffff888012041b40
raw: 0000000000000000 0000000000100010 00000001ffffffff 0000000000000000
page dumped because: kasan: bad access detected
page_owner tracks the page as allocated
page last allocated via order 1, migratetype Unmovable, gfp_mask 0xd20c0(__GFP_IO|__GFP_FS|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC), pid 2, tgid 2 (kthreadd), ts 6665465857, free_ts 0
prep_new_page mm/page_alloc.c:2532 [inline]
get_page_from_freelist+0x742/0x7c0 mm/page_alloc.c:4283
__alloc_pages+0x259/0x560 mm/page_alloc.c:5549
alloc_slab_page+0x70/0xf0 mm/slub.c:1829
allocate_slab+0x5e/0x520 mm/slub.c:1974
new_slab mm/slub.c:2034 [inline]
___slab_alloc+0x3ee/0xc40 mm/slub.c:3036
__slab_alloc mm/slub.c:3123 [inline]
slab_alloc_node mm/slub.c:3214 [inline]
slab_alloc mm/slub.c:3256 [inline]
kmem_cache_alloc_trace+0x25f/0x310 mm/slub.c:3287
kmalloc include/linux/slab.h:600 [inline]
kzalloc include/linux/slab.h:733 [inline]
set_kthread_struct+0xb1/0x1f0 kernel/kthread.c:117
copy_process+0x134a/0x4000 kernel/fork.c:2182
kernel_clone+0x21f/0x790 kernel/fork.c:2673
kernel_thread+0x150/0x1d0 kernel/fork.c:2726
create_kthread kernel/kthread.c:399 [inline]
kthreadd+0x57c/0x750 kernel/kthread.c:746
ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:306
page_owner free stack trace missing

Memory state around the buggy address:
ffff88801f816100: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
ffff88801f816180: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>ffff88801f816200: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
^
ffff88801f816280: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff88801f816300: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
==================================================================


---
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[Ryusuke Konishi]

This is the same UAF bug as below:

#syz dup: KASAN: use-after-free Read in nilfs_segctor_confirm

The bugfix for this is the patch titled "nilfs2: fix use-after-free
bug of struct nilfs_root", which was merged in the mainline after the
tested commit.

I confirmed this patch fixes the UAF bug with the reproducer.

Ryusuke Konishi