On 6/9/17, wm4 <nfx...@googlemail.com> wrote: > On Fri, 9 Jun 2017 00:10:49 +0200 > Michael Niedermayer <mich...@niedermayer.cc> wrote: > >> On Sat, May 27, 2017 at 12:24:16PM +0200, wm4 wrote: >> > On Sat, 27 May 2017 03:56:42 +0200 >> > Michael Niedermayer <mich...@niedermayer.cc> wrote: >> > >> > > On Fri, May 26, 2017 at 07:06:44PM -0400, Ronald S. Bultje wrote: >> > > > Hi, >> > > > >> > > > On Fri, May 26, 2017 at 6:34 PM, Michael Niedermayer >> > > > <mich...@niedermayer.cc >> > > > > wrote: >> > > > >> > > > > On Fri, May 26, 2017 at 06:07:35PM -0400, Ronald S. Bultje wrote: >> > > > > >> > > > > > Hi, >> > > > > > >> > > > > > On Fri, May 26, 2017 at 5:50 PM, Michael Niedermayer >> > > > > <mich...@niedermayer.cc >> > > > > > > wrote: >> > > > > > >> > > > > > > On Fri, May 26, 2017 at 11:18:12PM +0200, Hendrik Leppkes >> > > > > > > wrote: >> > > > > > > > On Fri, May 26, 2017 at 11:11 PM, Michael Niedermayer >> > > > > > > > <mich...@niedermayer.cc> wrote: >> > > > > > > > > On Fri, May 26, 2017 at 03:20:14PM +0100, Rostislav >> > > > > > > > > Pehlivanov >> > > > > wrote: >> > > > > > > > >> On 26 May 2017 at 12:21, wm4 <nfx...@googlemail.com> >> > > > > > > > >> wrote: >> > > > > > > > >> >> > > > > > > > >> > On Thu, 25 May 2017 16:10:49 +0200 >> > > > > > > > >> > Michael Niedermayer <mich...@niedermayer.cc> wrote: >> > > > > > > > >> > >> > > > > > > > >> > > Fixes: >> > > > > > > > >> > > 1735/clusterfuzz-testcase-minimized-5350472347025408 >> > > > > > > > >> > > >> > > > > > > > >> > > Found-by: continuous fuzzing process >> > > > > > > https://github.com/google/oss- >> > > > > > > > >> > fuzz/tree/master/projects/ffmpeg >> > > > > > > > >> > > Signed-off-by: Michael Niedermayer >> > > > > > > > >> > > <mich...@niedermayer.cc> >> > > > > > > > >> > > --- >> > > > > > > > >> > > libavcodec/fft_template.c | 50 >> > > > > > > > >> > > +++++++++++++++++++++++------- >> > > > > > > > >> > ----------------- >> > > > > > > > >> > > 1 file changed, 25 insertions(+), 25 deletions(-) >> > > > > > > > >> > > >> > > > > > > > >> > > diff --git a/libavcodec/fft_template.c >> > > > > b/libavcodec/fft_template.c >> > > > > > > > >> > > index 480557f49f..e3a37e5d69 100644 >> > > > > > > > >> > > --- a/libavcodec/fft_template.c >> > > > > > > > >> > > +++ b/libavcodec/fft_template.c >> > > > > > > > >> > > @@ -249,7 +249,7 @@ static void fft_calc_c(FFTContext >> > > > > > > > >> > > *s, >> > > > > > > FFTComplex *z) >> > > > > > > > >> > { >> > > > > > > > >> > > >> > > > > > > > >> > > int nbits, i, n, num_transforms, offset, step; >> > > > > > > > >> > > int n4, n2, n34; >> > > > > > > > >> > > - FFTSample tmp1, tmp2, tmp3, tmp4, tmp5, tmp6, >> > > > > > > > >> > > tmp7, tmp8; >> > > > > > > > >> > > + SUINT tmp1, tmp2, tmp3, tmp4, tmp5, tmp6, tmp7, >> > > > > > > > >> > > tmp8; >> > > > > > > > >> > >> > > > > > > > >> > I want this SUINT thing gone, not have more of it. >> > > > > > > > >> > _______________________________________________ >> > > > > > > > >> > ffmpeg-devel mailing list >> > > > > > > > >> > ffmpeg-devel@ffmpeg.org >> > > > > > > > >> > http://ffmpeg.org/mailman/listinfo/ffmpeg-devel >> > > > > > > > >> > >> > > > > > > > >> >> > > > > > > > >> I agree, especially here. >> > > > > > > > > >> > > > > > > > >> Overflows should be left to happen in transforms if the >> > > > > > > > >> input is >> > > > > > > corrupt. >> > > > > > > > > >> > > > > > > > > signed int overflow is not allowed in C, if that is what >> > > > > > > > > you meant. >> > > > > > > > > >> > > > > > > > > >> > > > > > > > >> > > > > > > > Its "undefined", which means what the result will be is not >> > > > > > > > defined - >> > > > > > > > which in such a DSP function is irrelevant, if all it causes >> > > > > > > > is >> > > > > > > > corrupt output ... from corrupt input. >> > > > > > > >> > > > > > > no, this is not correct. >> > > > > > > undefined behavior does not mean the effect will be limited to >> > > > > > > the output. >> > > > > > > It could cause the process to hard lockup, trigger an >> > > > > > > exception or >> > > > > > > set a flag causing errors in later unrelated code. >> > > > > > >> > > > > > >> > > > > >> > > > > > We've discussed this before, if you believe this to be >> > > > > > exploitable, why >> > > > > > allow it in our repository at all? I know of no other project >> > > > > > that even >> > > > > > remotely allows such ridiculous things. Please limit exploitable >> > > > > > code to >> > > > > > your personal tree, ffmpeg is not a rootkit. >> > > > > >> > > > > please calm down, you make all kinds of statments and implications >> > > > > in >> > > > > the text above which are not true. >> > > > > >> > > > > This specific code in git triggers undefined behavior, the patch >> > > > > fixes >> > > > > this undefined behavior. >> > > > > If that is exploitable (which i neither claim it is nor that it >> > > > > isnt) >> > > > > its a issue that exists before the patch but not afterwards. >> > > > >> > > > >> > > >> > > > *unsigned* removes the exploit. SUINT keeps it, and is therefore >> > > > part of a >> > > > rootkit. >> > > >> > > SUINT is defined to unsigned, if unsigned removes the issue >> > > so does SUINT. >> > >> > Then why is it called SUINT and not UINT. >> >> Signed value in >> Unsigned >> INTeger type >> >> This concept is needed for fixing undefined operations efficiently. >> The type can always be replaced by unsigned and thats what is being >> done now. >> But it makes the code hard to understand and maintain because these >> values are not positive integers but signed integers. Which for >> C standard compliance need to be stored in a unsigned type. >> >> Both SUINT and unsigned should produce identical binaries but unsigned > > Is that so? Then please add a FATE check that guarantees this. > >> is semantically wrong. > > If it's wrong then it shouldn't be used.
I think you should read (again) these articles: http://blog.llvm.org/2011/05/what-every-c-programmer-should-know.html _______________________________________________ ffmpeg-devel mailing list ffmpeg-devel@ffmpeg.org http://ffmpeg.org/mailman/listinfo/ffmpeg-devel
