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Re: [PATCH] lib/strscpy: avoid KASAN false positive

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On Tue, Jul 18, 2017 at 1:15 PM, Andrey Ryabinin
<aryabinin@virtuozzo.com> wrote:
>
> No, it does warn about valid users. The report that Dave posted wasn't about wrong strscpy() usage
> it was about reading 8-bytes from 5-bytes source string. It wasn't about buggy 'count' at all.
> So KASAN will warn for perfectly valid code like this:
>         char dest[16];
>         strscpy(dest, "12345", sizeof(dest)):

Ugh, ok, yes.

> For strscpy() that would mean making the *whole* read from 'src' buffer unchecked by KASAN.

So we do have that READ_ONCE_NOCHECK(), but could we perhaps have
something that doesn't do a NOCHECK but a partial check and is simply
ok with "this is an optimistc longer access"

We have that for the dcache case too, although there the code does
that odd kasan_unpoison_shadow() instead.

                 Linus

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Re: [PATCH] lib/strscpy: avoid KASAN false positive Linus Torvalds <torvalds@linux-foundation.org> - 2017-07-18 19:30 +0200
  Re: [PATCH] lib/strscpy: avoid KASAN false positive Linus Torvalds <torvalds@linux-foundation.org> - 2017-07-18 22:30 +0200
    Re: [PATCH] lib/strscpy: avoid KASAN false positive Andrew Morton <akpm@linux-foundation.org> - 2017-07-19 00:10 +0200
      Re: [PATCH] lib/strscpy: avoid KASAN false positive Linus Torvalds <torvalds@linux-foundation.org> - 2017-07-19 00:40 +0200
        Re: [PATCH] lib/strscpy: avoid KASAN false positive Dmitry Vyukov <dvyukov@google.com> - 2017-07-19 09:50 +0200
      Re: [PATCH] lib/strscpy: avoid KASAN false positive Dave Jones <davej@codemonkey.org.uk> - 2017-07-19 18:10 +0200
        Re: [PATCH] lib/strscpy: avoid KASAN false positive Dmitry Vyukov <dvyukov@google.com> - 2017-07-26 14:10 +0200

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