Re: BUG: unable to handle kernel NULL pointer dereference in call_rcu

[Dmitry Vyukov <dvyukov@google.com>]

/\/\/\/\On Sun, Dec 27, 2020 at 8:45 PM Andrew Morton
<akpm@linux-foundation.org> wrote:
>
> (cc KASAN developers)
>
> On Sat, 26 Dec 2020 15:25:14 -0800 syzbot <syzbot+9d3ede723bdc58553f13@syzkaller.appspotmail.com> wrote:
>
> > Hello,
> >
> > syzbot found the following issue on:
> >
> > HEAD commit:    614cb589 Merge tag 'acpi-5.11-rc1-2' of git://git.kernel.o..
> > git tree:       upstream
> > console output: https://syzkaller.appspot.com/x/log.txt?x=10a82a50d00000
> > kernel config:  https://syzkaller.appspot.com/x/.config?x=bf519e1e96191576
> > dashboard link: https://syzkaller.appspot.com/bug?extid=9d3ede723bdc58553f13
> > compiler:       gcc (GCC) 10.1.0-syz 20200507
> > syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=11830e93500000
> > C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=13d92057500000
> >
> > IMPORTANT: if you fix the issue, please add the following tag to the commit:
> > Reported-by: syzbot+9d3ede723bdc58553f13@syzkaller.appspotmail.com
> >
> > BUG: kernel NULL pointer dereference, address: 0000000000000008
> > #PF: supervisor read access in kernel mode
> > #PF: error_code(0x0000) - not-present page
> > PGD 2d993067 P4D 2d993067 PUD 19a3c067 PMD 0
> > Oops: 0000 [#1] PREEMPT SMP KASAN
> > CPU: 1 PID: 3852 Comm: kworker/1:2 Not tainted 5.10.0-syzkaller #0
> > Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
> > Workqueue: events free_ipc
> > RIP: 0010:kasan_record_aux_stack+0x77/0xb0 mm/kasan/generic.c:341

+Walter, Andrey

void kasan_record_aux_stack(void *addr)
{
    ...
    alloc_meta = kasan_get_alloc_meta(cache, object);
    alloc_meta->aux_stack[1] = alloc_meta->aux_stack[0];

/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\
It crashes on NULL deref here, I assume alloc_meta is NULL. We may not
have it for some slabs. Do we miss a NULL check here?




> > Code: 48 f7 fe 8b 47 24 49 89 f0 48 29 d3 8d 70 ff 41 0f af f0 48 01 ce 48 39 f3 48 0f 46 f3 e8 81 e9 ff ff bf 00 08 00 00 48 89 c3 <8b> 40 08 89 43 0c e8 1e e6 ff ff 89 43 08 5b c3 48 8b 50 08 48 c7
> > RSP: 0018:ffffc90002e6fae8 EFLAGS: 00010046
> > RAX: 0000000000000000 RBX: 0000000000000000 RCX: ffff888039800000
> > RDX: 0000000000000078 RSI: ffff888039800000 RDI: 0000000000000800
> > RBP: ffffffff837ef3a0 R08: 0000000000400000 R09: 000000000000002e
> > R10: ffffffff8132b7ea R11: 000000000000003f R12: 0000000000035b40
> > R13: ffff888039800088 R14: ffffc90002e6fc08 R15: 0000000000000200
> > FS:  0000000000000000(0000) GS:ffff8880b9d00000(0000) knlGS:0000000000000000
> > CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> > CR2: 0000000000000008 CR3: 0000000011841000 CR4: 00000000001506e0
> > DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> > DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
> > Call Trace:
> >  __call_rcu kernel/rcu/tree.c:2965 [inline]
> >  call_rcu+0xbb/0x710 kernel/rcu/tree.c:3038
> >  ipc_rcu_putref+0x83/0xb0 ipc/util.c:505
> >  freeary+0x139c/0x1b30 ipc/sem.c:1188
> >  free_ipcs+0x98/0x1e0 ipc/namespace.c:112
> >  sem_exit_ns+0x1b/0x40 ipc/sem.c:260
> >  free_ipc_ns ipc/namespace.c:124 [inline]
> >  free_ipc+0xf8/0x200 ipc/namespace.c:141
> >  process_one_work+0x98d/0x1630 kernel/workqueue.c:2275
> >  worker_thread+0x64c/0x1120 kernel/workqueue.c:2421
> >  kthread+0x3b1/0x4a0 kernel/kthread.c:292
> >  ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:296
> > Modules linked in:
> > CR2: 0000000000000008
> > ---[ end trace 28dc093e61d44dc2 ]---
> > RIP: 0010:kasan_record_aux_stack+0x77/0xb0 mm/kasan/generic.c:341
> > Code: 48 f7 fe 8b 47 24 49 89 f0 48 29 d3 8d 70 ff 41 0f af f0 48 01 ce 48 39 f3 48 0f 46 f3 e8 81 e9 ff ff bf 00 08 00 00 48 89 c3 <8b> 40 08 89 43 0c e8 1e e6 ff ff 89 43 08 5b c3 48 8b 50 08 48 c7
> > RSP: 0018:ffffc90002e6fae8 EFLAGS: 00010046
> > RAX: 0000000000000000 RBX: 0000000000000000 RCX: ffff888039800000
> > RDX: 0000000000000078 RSI: ffff888039800000 RDI: 0000000000000800
> > RBP: ffffffff837ef3a0 R08: 0000000000400000 R09: 000000000000002e
> > R10: ffffffff8132b7ea R11: 000000000000003f R12: 0000000000035b40
> > R13: ffff888039800088 R14: ffffc90002e6fc08 R15: 0000000000000200
> > FS:  0000000000000000(0000) GS:ffff8880b9d00000(0000) knlGS:0000000000000000
> > CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> > CR2: 0000000000000008 CR3: 0000000011841000 CR4: 00000000001506e0
> > DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> > DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
> >
> >
> > ---
> > This report is generated by a bot. It may contain errors.
> > See https://goo.gl/tpsmEJ for more information about syzbot.
> > syzbot engineers can be reached at syzkaller@googlegroups.com.
> >
> > syzbot will keep track of this issue. See:
> > https://goo.gl/tpsmEJ#status for how to communicate with syzbot.
> > syzbot can test patches for this issue, for details see:
> > https://goo.gl/tpsmEJ#testing-patches