Re: KASAN: user-memory-access Read in vdso_fault

[Dmitry Vyukov]

On Thu, Sep 24, 2020 at 11:42 AM syzbot
<syzbot+fe2a9f19481e3bfed524@xxxxxxxxxxxxxxxxxxxxxxxxx> wrote:
>
> Hello,
>
> syzbot found the following issue on:
>
> HEAD commit:    eb5f95f1 Merge tag 's390-5.9-6' of git://git.kernel.org/pu..
> git tree:       upstream
> console output: https://syzkaller.appspot.com/x/log.txt?x=1077ecc3900000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=cd992d74d6c7e62
> dashboard link: https://syzkaller.appspot.com/bug?extid=fe2a9f19481e3bfed524
> compiler:       clang version 10.0.0 (https://github.com/llvm/llvm-project/ c2443155a0fb245c8f17f2c1c72b6ea391e86e81)
>
> Unfortunately, I don't have any reproducer for this issue yet.
>
> IMPORTANT: if you fix the issue, please add the following tag to the commit:
> Reported-by: syzbot+fe2a9f19481e3bfed524@xxxxxxxxxxxxxxxxxxxxxxxxx

There is strong indication that this is a manifestation of the same
problem we see in other crashes.
Let's make one canonical bug for this:

#syz dup: general protection fault in perf_misc_flags

> ==================================================================
> BUG: KASAN: user-memory-access in vdso_fault+0xc1/0x1b0 arch/x86/entry/vdso/vma.c:67
> Read of size 8 at addr 000000001953fc48 by task systemd-udevd/9883
>
> CPU: 0 PID: 9883 Comm: systemd-udevd Not tainted 5.9.0-rc5-syzkaller #0
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
> Call Trace:
>  __dump_stack lib/dump_stack.c:77 [inline]
>  dump_stack+0x1d6/0x29e lib/dump_stack.c:118
>  __kasan_report mm/kasan/report.c:517 [inline]
>  kasan_report+0x151/0x1d0 mm/kasan/report.c:530
>  vdso_fault+0xc1/0x1b0 arch/x86/entry/vdso/vma.c:67
>  __do_fault+0x138/0x3b0 mm/memory.c:3450
>  do_read_fault+0x5a6/0x9e0 mm/memory.c:3843
>  do_fault mm/memory.c:3971 [inline]
>  handle_pte_fault mm/memory.c:4211 [inline]
>  __handle_mm_fault mm/memory.c:4346 [inline]
>  handle_mm_fault+0x1d73/0x29a0 mm/memory.c:4444
>  do_user_addr_fault+0x515/0xa90 arch/x86/mm/fault.c:1372
>  handle_page_fault arch/x86/mm/fault.c:1429 [inline]
>  exc_page_fault+0x129/0x240 arch/x86/mm/fault.c:1482
>  asm_exc_page_fault+0x1e/0x30 arch/x86/include/asm/idtentry.h:538
> RIP: 0033:0x7ffedaddb630
> Code: Bad RIP value.
> RSP: 002b:00007ffedad997b8 EFLAGS: 00010246
> RAX: 0000000000000000 RBX: 0000000000000000 RCX: 0000000000000015
> RDX: 0000000058585858 RSI: 0000000000000000 RDI: 00007ffedad997e0
> RBP: 0000000000000000 R08: 000000000000fefe R09: 0000000000000030
> R10: 0000000000000000 R11: 0000000000000206 R12: 000055e855d83675
> R13: 00007ffedad99938 R14: 0000000000080000 R15: 000055e855d83660
> ==================================================================
>
>
> ---
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