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[68.56.149.176]) by smtp.gmail.com with ESMTPSA id 6a1803df08f44-6b61b9c4d9fsm11755926d6.3.2024.07.09.13.19.08 for <ffmpeg-devel@ffmpeg.org> (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 09 Jul 2024 13:19:09 -0700 (PDT) Message-ID: <81b76fa0-6eb3-4619-8878-488bc8886448@gmail.com> Date: Tue, 9 Jul 2024 16:19:08 -0400 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird To: ffmpeg-devel@ffmpeg.org References: <20240708042517.5585-1-gseanmcg@gmail.com> <20240709183434.10114-1-gseanmcg@gmail.com> Content-Language: en-US-large From: Leo Izen <leo.izen@gmail.com> Autocrypt: addr=leo.izen@gmail.com; keydata= xjMEZZw8HxYJKwYBBAHaRw8BAQdAgcfI+LbtjWarA7LQu6/WAPlKkn9tn4HalmHgGVhMUdzN KkxlbyBJemVuIChUcmFuZXB0b3JhKSA8bGVvLml6ZW5AZ21haWwuY29tPsKTBBMWCgA7FiEE HYMKC85GcJ4gOyb8dk5I6kgiGDMFAmWcPB8CGwMFCwkIBwICIgIGFQoJCAsCBBYCAwECHgcC F4AACgkQdk5I6kgiGDOnGAEA+oJFwblAblnhK+T5a5EuEbXMTZG4FkYTYz0VmjJ0NHIA/Rn9 ZE9+EEsH8fmT0hRJSiM3+zbkwQJA9gVVYAek9kMKzjgEZZw8HxIKKwYBBAGXVQEFAQEHQDes 4thejF9AU2rkGuDuut3CQYwB4SVpI4EzU8uvPJgfAwEIB8J4BBgWCgAgFiEEHYMKC85GcJ4g Oyb8dk5I6kgiGDMFAmWcPB8CGwwACgkQdk5I6kgiGDOv3QD+PLXrL0Ihk675Ip5FG+VJOodN 6e+5n3iYC6wJ75eqG3EA/1nCywoGXlCYuzXgq3el6NOn+8awwaXcTVJFzZCRbe8M In-Reply-To: <20240709183434.10114-1-gseanmcg@gmail.com> Subject: Re: [FFmpeg-devel] [PATCHv3] swscale: prevent undefined behaviour in the PUTRGBA macro X-BeenThere: ffmpeg-devel@ffmpeg.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: FFmpeg development discussions and patches <ffmpeg-devel.ffmpeg.org> List-Unsubscribe: <https://ffmpeg.org/mailman/options/ffmpeg-devel>, <mailto:ffmpeg-devel-request@ffmpeg.org?subject=unsubscribe> List-Archive: <https://ffmpeg.org/pipermail/ffmpeg-devel> List-Post: <mailto:ffmpeg-devel@ffmpeg.org> List-Help: <mailto:ffmpeg-devel-request@ffmpeg.org?subject=help> List-Subscribe: <https://ffmpeg.org/mailman/listinfo/ffmpeg-devel>, <mailto:ffmpeg-devel-request@ffmpeg.org?subject=subscribe> Reply-To: FFmpeg development discussions and patches <ffmpeg-devel@ffmpeg.org> Content-Transfer-Encoding: 7bit Content-Type: text/plain; charset="us-ascii"; Format="flowed" Errors-To: ffmpeg-devel-bounces@ffmpeg.org Sender: "ffmpeg-devel" <ffmpeg-devel-bounces@ffmpeg.org> Archived-At: <https://master.gitmailbox.com/ffmpegdev/81b76fa0-6eb3-4619-8878-488bc8886448@gmail.com/> List-Archive: <https://master.gitmailbox.com/ffmpegdev/> List-Post: <mailto:ffmpegdev@gitmailbox.com> On 7/9/24 2:34 PM, Sean McGovern wrote: > For even small values of 'asrc', shifting them by 24 bits or more > will cause arithmetic overflow and be caught by > GCC's undefined behaviour sanitizer. > > Ensure the values do not overflow by up-casting the bracketed > expressions involving 'asrc' to int32_t. > --- > libswscale/yuv2rgb.c | 4 ++-- > 1 file changed, 2 insertions(+), 2 deletions(-) > > diff --git a/libswscale/yuv2rgb.c b/libswscale/yuv2rgb.c > index 977eb3a7dd..ac0b811f61 100644 > --- a/libswscale/yuv2rgb.c > +++ b/libswscale/yuv2rgb.c > @@ -100,9 +100,9 @@ const int *sws_getCoefficients(int colorspace) > > #define PUTRGBA(dst, ysrc, asrc, i, abase) \ > Y = ysrc[2 * i]; \ > - dst[2 * i] = r[Y] + g[Y] + b[Y] + (asrc[2 * i] << abase); \ > + dst[2 * i] = r[Y] + g[Y] + b[Y] + ((int32_t)(asrc[2 * i]) << abase); \ > Y = ysrc[2 * i + 1]; \ > - dst[2 * i + 1] = r[Y] + g[Y] + b[Y] + (asrc[2 * i + 1] << abase); > + dst[2 * i + 1] = r[Y] + g[Y] + b[Y] + ((int32_t)(asrc[2 * i + 1]) << abase); > > #define PUTRGB48(dst, src, asrc, i, abase) \ > Y = src[ 2 * i]; \ Are these able to be negative? If not, it may be wise to cast to uint32_t instead as left shifting a negative integer is UB. - Leo Izen (Traneptora) _______________________________________________ ffmpeg-devel mailing list ffmpeg-devel@ffmpeg.org https://ffmpeg.org/mailman/listinfo/ffmpeg-devel To unsubscribe, visit link above, or email ffmpeg-devel-request@ffmpeg.org with subject "unsubscribe".