On Sun, Nov 08, 2015 at 05:12:37PM +0100, Andreas Cadhalpun wrote: > On 08.11.2015 01:02, Michael Niedermayer wrote: > > On Sun, Nov 08, 2015 at 12:09:02AM +0100, Andreas Cadhalpun wrote: > >> Mathematically this is bogus, but it is much better than the previous > >> behaviour: returning a random value from an out of bounds read. > >> > >> Returning zero will just lead to division by zero problems. > >> > >> This fixes av_assert2 failures in the aac_fixed decoder. > >> > >> Signed-off-by: Andreas Cadhalpun <andreas.cadhal...@googlemail.com> > >> --- > >> libavutil/softfloat.h | 2 ++ > >> 1 file changed, 2 insertions(+) > >> > >> diff --git a/libavutil/softfloat.h b/libavutil/softfloat.h > >> index fefde8c..0a2074a 100644 > >> --- a/libavutil/softfloat.h > >> +++ b/libavutil/softfloat.h > >> @@ -170,6 +170,8 @@ static av_always_inline SoftFloat av_sqrt_sf(SoftFloat > >> val) > >> > >> if (val.mant == 0) > >> val.exp = 0; > >> + else if (val.mant < 0) > >> + val = FLOAT_1; > > > > this is IMHO not ok > > sqrt(-1) has 3 sane possible outcomes > > 1. the complex number i > > 2. NaN > > 3. abort() > > OK, attached is a patch adding an assert instead. > > > like division by 0 sqare roots of negative numbers in a context of > > real values are a bug, there is likely something wrong in the code > > that is calling sqrt with a negative number and simply returning 1 > > silently would make it hard to find and debug such bugs > > Returning a random number also makes it hard to debug such bugs... > > Anyway, this bug happens in sbr_gain_calc, if sbr->e_curr[e][m] > is smaller than -1. The reason for that is sbr_sum_square_c returning > a negative value, because accu overflows. > I'll send a patch for that, but there are also lots of other > overflows happening in the aac_fixed decoder. > > Best regards, > Andreas >
> softfloat.h | 2 ++ > 1 file changed, 2 insertions(+) > 743e46bfbb223cee2d34e8db896758d59dcc308a > 0001-softfloat-assert-when-the-argument-of-av_sqrt_sf-is-.patch > From 2eb7607e3ead91c2cb35076c94746405183d0320 Mon Sep 17 00:00:00 2001 > From: Andreas Cadhalpun <andreas.cadhal...@googlemail.com> > Date: Sun, 8 Nov 2015 15:15:24 +0100 > Subject: [PATCH] softfloat: assert when the argument of av_sqrt_sf is negative > > The correct result can't be expressed in SoftFloat. > Currently it returns a random value from an out of bounds read. > > Signed-off-by: Andreas Cadhalpun <andreas.cadhal...@googlemail.com> > --- > libavutil/softfloat.h | 2 ++ > 1 file changed, 2 insertions(+) LGTM thanks [...] -- Michael GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB Those who are too smart to engage in politics are punished by being governed by those who are dumber. -- Plato
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