ffmpeg | branch: release/2.2 | wm4 <nfx...@googlemail.com> | Thu Jan 8 17:19:17 2015 +0100| [a4a87a7efd8b72c0871491bcc85330e14beb8bd6] | committer: Michael Niedermayer
avcodec/dvdsubdec: fix accessing dangling pointers dvdsub_decode() can call append_to_cached_buf() 2 times, the second time with ctx->buf as argument. If the second append_to_cached_buf() reallocs ctx->buf, the argument will be a pointer to the previous, freed block. This can cause invalid reads at least with some fuzzed files - and possibly with valid files. Since packets can apparently not be larger than 64K (even if packets are combined), just use a fixed size buffer. It will be allocated as part of the DVDSubContext, and although some memory is "wasted", it's relatively minimal by modern standards and should be acceptable. Signed-off-by: Michael Niedermayer <michae...@gmx.at> (cherry picked from commit 816577716bc6170bccfea3b9e865618b69a4b426) Signed-off-by: Michael Niedermayer <michae...@gmx.at> > http://git.videolan.org/gitweb.cgi/ffmpeg.git/?a=commit;h=a4a87a7efd8b72c0871491bcc85330e14beb8bd6 --- libavcodec/dvdsubdec.c | 12 +++--------- 1 file changed, 3 insertions(+), 9 deletions(-) diff --git a/libavcodec/dvdsubdec.c b/libavcodec/dvdsubdec.c index 122a4c7..ee6aaf6 100644 --- a/libavcodec/dvdsubdec.c +++ b/libavcodec/dvdsubdec.c @@ -37,7 +37,7 @@ typedef struct DVDSubContext int has_palette; uint8_t colormap[4]; uint8_t alpha[256]; - uint8_t *buf; + uint8_t buf[0x10000]; int buf_size; #ifdef DEBUG int sub_id; @@ -502,15 +502,11 @@ static int append_to_cached_buf(AVCodecContext *avctx, { DVDSubContext *ctx = avctx->priv_data; - if (ctx->buf_size > 0xffff - buf_size) { + if (ctx->buf_size >= sizeof(ctx->buf) - buf_size) { av_log(avctx, AV_LOG_WARNING, "Attempt to reconstruct " "too large SPU packets aborted.\n"); - av_freep(&ctx->buf); return AVERROR_INVALIDDATA; } - ctx->buf = av_realloc(ctx->buf, ctx->buf_size + buf_size); - if (!ctx->buf) - return AVERROR(ENOMEM); memcpy(ctx->buf + ctx->buf_size, buf, buf_size); ctx->buf_size += buf_size; return 0; @@ -526,7 +522,7 @@ static int dvdsub_decode(AVCodecContext *avctx, AVSubtitle *sub = data; int is_menu; - if (ctx->buf) { + if (ctx->buf_size) { int ret = append_to_cached_buf(avctx, buf, buf_size); if (ret < 0) { *data_size = 0; @@ -564,7 +560,6 @@ static int dvdsub_decode(AVCodecContext *avctx, } #endif - av_freep(&ctx->buf); ctx->buf_size = 0; *data_size = 1; return buf_size; @@ -646,7 +641,6 @@ static av_cold int dvdsub_init(AVCodecContext *avctx) static av_cold int dvdsub_close(AVCodecContext *avctx) { DVDSubContext *ctx = avctx->priv_data; - av_freep(&ctx->buf); ctx->buf_size = 0; return 0; } _______________________________________________ ffmpeg-cvslog mailing list ffmpeg-cvslog@ffmpeg.org http://ffmpeg.org/mailman/listinfo/ffmpeg-cvslog