Re: [syzbot] [bcachefs?] KASAN: global-out-of-bounds Read in rcu_pending_exit

syzbot
2024-12-19T09:53:23Z

syzbot has found a reproducer for the following issue on:

HEAD commit: eabcdba3ad40 Merge tag 'for-6.13-rc3-tag' of git://git.ker..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=170e77e8580000
kernel config: https://syzkaller.appspot.com/x/.config?x=1234f097ee657d8b
dashboard link: https://syzkaller.appspot.com/bug?extid=e733ab672a1b6724c27f
compiler: Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=12834cf8580000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/7a4dff87674a/disk-eabcdba3.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/266bc2b7ced3/vmlinux-eabcdba3.xz
kernel image: https://storage.googleapis.com/syzbot-assets/ee4bcd9be832/bzImage-eabcdba3.xz
mounted in repro: https://storage.googleapis.com/syzbot-assets/7bfbea1d3e96/mount_2.gz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+e733ab672a1b6724c27f@syzkaller.appspotmail.com

------------[ cut here ]------------
==================================================================
BUG: KASAN: global-out-of-bounds in string_nocheck lib/vsprintf.c:646 [inline]
BUG: KASAN: global-out-of-bounds in string+0x218/0x2b0 lib/vsprintf.c:728
Read of size 1 at addr ffffffff8c53984a by task syz.0.174/7554

CPU: 1 UID: 0 PID: 7554 Comm: syz.0.174 Not tainted 6.13.0-rc3-syzkaller-00073-geabcdba3ad40 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 11/25/2024
Call Trace:
<TASK>
__dump_stack lib/dump_stack.c:94 [inline]
dump_stack_lvl+0x241/0x360 lib/dump_stack.c:120
print_address_description mm/kasan/report.c:378 [inline]
print_report+0x169/0x550 mm/kasan/report.c:489
kasan_report+0x143/0x180 mm/kasan/report.c:602
string_nocheck lib/vsprintf.c:646 [inline]
string+0x218/0x2b0 lib/vsprintf.c:728
vsnprintf+0x1101/0x1da0 lib/vsprintf.c:2848
vprintk_store+0x485/0x1240 kernel/printk/printk.c:2279
vprintk_emit+0x271/0xa10 kernel/printk/printk.c:2408
__warn_printk+0x263/0x360 kernel/panic.c:797
look_up_lock_class+0xdb/0x170 kernel/locking/lockdep.c:936
register_lock_class+0x102/0x980 kernel/locking/lockdep.c:1290
__lock_acquire+0xf3/0x2100 kernel/locking/lockdep.c:5101
lock_acquire+0x1ed/0x550 kernel/locking/lockdep.c:5849
__raw_spin_lock_irq include/linux/spinlock_api_smp.h:119 [inline]
_raw_spin_lock_irq+0xd3/0x120 kernel/locking/spinlock.c:170
spin_lock_irq include/linux/spinlock.h:376 [inline]
rcu_pending_has_pending_or_armed fs/bcachefs/rcu_pending.c:576 [inline]
rcu_pending_exit+0x13f/0x7a0 fs/bcachefs/rcu_pending.c:594
bch2_fs_btree_key_cache_exit+0x97f/0xab0 fs/bcachefs/btree_key_cache.c:741
__bch2_fs_free fs/bcachefs/super.c:556 [inline]
bch2_fs_release+0x206/0x7d0 fs/bcachefs/super.c:611
kobject_cleanup lib/kobject.c:689 [inline]
kobject_release lib/kobject.c:720 [inline]
kref_put include/linux/kref.h:65 [inline]
kobject_put+0x22f/0x480 lib/kobject.c:737
bch2_fs_alloc fs/bcachefs/super.c:960 [inline]
bch2_fs_open+0x1ebe/0x2f80 fs/bcachefs/super.c:2065
bch2_fs_get_tree+0x738/0x1710 fs/bcachefs/fs.c:2157
vfs_get_tree+0x90/0x2b0 fs/super.c:1814
do_new_mount+0x2be/0xb40 fs/namespace.c:3507
do_mount fs/namespace.c:3847 [inline]
__do_sys_mount fs/namespace.c:4057 [inline]
__se_sys_mount+0x2d6/0x3c0 fs/namespace.c:4034
do_syscall_x64 arch/x86/entry/common.c:52 [inline]
do_syscall_64+0xf3/0x230 arch/x86/entry/common.c:83
entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7fb98f7874ca
Code: d8 64 89 02 48 c7 c0 ff ff ff ff eb a6 e8 de 1a 00 00 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 49 89 ca b8 a5 00 00 00 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:00007fb99051be68 EFLAGS: 00000246 ORIG_RAX: 00000000000000a5
RAX: ffffffffffffffda RBX: 00007fb99051bef0 RCX: 00007fb98f7874ca
RDX: 00000000200000c0 RSI: 0000000020000000 RDI: 00007fb99051beb0
RBP: 00000000200000c0 R08: 00007fb99051bef0 R09: 0000000000800000
R10: 0000000000800000 R11: 0000000000000246 R12: 0000000020000000
R13: 00007fb99051beb0 R14: 0000000000005938 R15: 0000000020005b00
</TASK>

The buggy address belongs to the variable:
.str+0xa/0x20

The buggy address belongs to the physical page:
page: refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0xc539
flags: 0xfff00000002000(reserved|node=0|zone=1|lastcpupid=0x7ff)
raw: 00fff00000002000 ffffea0000314e48 ffffea0000314e48 0000000000000000
raw: 0000000000000000 0000000000000000 00000001ffffffff 0000000000000000
page dumped because: kasan: bad access detected
page_owner info is not present (never set?)

Memory state around the buggy address:
ffffffff8c539700: 02 f9 f9 f9 00 00 06 f9 f9 f9 f9 f9 00 00 03 f9
ffffffff8c539780: f9 f9 f9 f9 00 00 00 00 f9 f9 f9 f9 00 00 00 00
>ffffffff8c539800: 00 00 00 00 00 00 00 00 00 01 f9 f9 00 00 00 04
^
ffffffff8c539880: f9 f9 f9 f9 00 00 00 00 00 00 00 00 00 00 00 00
ffffffff8c539900: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
==================================================================

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