From 3e8e1a660ea182111057d56ec1cfad2c62250f4c Mon Sep 17 00:00:00 2001 From: Andreas Cadhalpun Date: Fri, 6 Nov 2015 23:44:01 +0100 Subject: apng: use correct size for output buffer The buffer needs s->bpp bytes, at maximum currently 10. Assert that s->bpp is not larger. This fixes a stack buffer overflow. Reviewed-by: wm4 Reviewed-by: Paul B Mahol Signed-off-by: Andreas Cadhalpun --- libavcodec/pngdec.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) (limited to 'libavcodec/pngdec.c') diff --git a/libavcodec/pngdec.c b/libavcodec/pngdec.c index 689aa2b562..feb17630a2 100644 --- a/libavcodec/pngdec.c +++ b/libavcodec/pngdec.c @@ -1016,7 +1016,7 @@ static int handle_p_frame_apng(AVCodecContext *avctx, PNGDecContext *s, for (x = s->x_offset; x < s->x_offset + s->cur_w; ++x, foreground += s->bpp, background += s->bpp) { size_t b; uint8_t foreground_alpha, background_alpha, output_alpha; - uint8_t output[4]; + uint8_t output[10]; // Since we might be blending alpha onto alpha, we use the following equations: // output_alpha = foreground_alpha + (1 - foreground_alpha) * background_alpha @@ -1056,6 +1056,8 @@ static int handle_p_frame_apng(AVCodecContext *avctx, PNGDecContext *s, output_alpha = foreground_alpha + FAST_DIV255((255 - foreground_alpha) * background_alpha); + av_assert0(s->bpp <= 10); + for (b = 0; b < s->bpp - 1; ++b) { if (output_alpha == 0) { output[b] = 0; -- cgit v1.2.3