[FFmpeg-devel] [PATCH 1/4] avutil/avstring: Fix bug and undefined behavior in av_strncasecmp()

[Michael Niedermayer]

On Tue, Apr 16, 2019 at 06:31:28PM +0200, Paul B Mahol wrote:
> On 4/16/19, Michael Niedermayer <michael at niedermayer.cc> wrote:
> > The function in case of n=0 would read more bytes than 0.
> > The end pointer could be beyond the allocated space, which
> > is undefined.
> >
> > Signed-off-by: Michael Niedermayer <michael at niedermayer.cc>
> > ---
> >  libavutil/avstring.c | 5 +++--
> >  1 file changed, 3 insertions(+), 2 deletions(-)
> >
> > diff --git a/libavutil/avstring.c b/libavutil/avstring.c
> > index f03dd25141..4c068f5bc5 100644
> > --- a/libavutil/avstring.c
> > +++ b/libavutil/avstring.c
> > @@ -222,12 +222,13 @@ int av_strcasecmp(const char *a, const char *b)
> >
> >  int av_strncasecmp(const char *a, const char *b, size_t n)
> >  {
> > -    const char *end = a + n;
> >      uint8_t c1, c2;
> > +    if (n <= 0)
> > +        return 0;
> >      do {
> >          c1 = av_tolower(*a++);
> >          c2 = av_tolower(*b++);
> > -    } while (a < end && c1 && c1 == c2);
> > +    } while (--n && c1 && c1 == c2);
> >      return c1 - c2;
> >  }
> >
> > --
> > 2.21.0
> >
> 
> LGTM

will apply

[...]
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Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

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