| Message ID | 20190623234231.6348-3-andreas.rheinhardt@gmail.com |
|---|---|
| State | Accepted |
| Commit | ff5ea59f7b05cb4d37ba9e2c3ee383ff24a10ae0 |
| Headers | show |
On 6/23/2019 8:42 PM, Andreas Rheinhardt wrote: > Up until now, when an element was skipped, it was relied upon > ffio_limit to make sure that there is enough data available to skip. > ffio_limit itself relies upon the availability of the file's size. As > this needn't be available, the check has been refined: First one byte > less than intended is skipped, then another byte is read, followed by a > check of the error flags. > > Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@gmail.com> > --- > libavformat/matroskadec.c | 24 +++++++++++++++++------- > 1 file changed, 17 insertions(+), 7 deletions(-) > > diff --git a/libavformat/matroskadec.c b/libavformat/matroskadec.c > index 1db7471440..caabfcf6ac 100644 > --- a/libavformat/matroskadec.c > +++ b/libavformat/matroskadec.c > @@ -1256,13 +1256,23 @@ static int ebml_parse_elem(MatroskaDemuxContext *matroska, > case EBML_STOP: > return 1; > default: > - if (ffio_limit(pb, length) != length) { > - // ffio_limit emits its own error message, > - // so we don't have to. > - return AVERROR(EIO); > - } > - res = avio_skip(pb, length); > - res = res < 0 ? res : 0; > + if (length) { > + if (ffio_limit(pb, length) != length) { > + // ffio_limit emits its own error message, > + // so we don't have to. > + return AVERROR(EIO); > + } > + if ((res = avio_skip(pb, length - 1)) >= 0) { > + // avio_skip might take us past EOF. We check for this > + // by skipping only length - 1 bytes, reading a byte and > + // checking the error flags. This is done in order to check > + // that the element has been properly skipped even when > + // no filesize (that ffio_limit relies on) is available. > + avio_r8(pb); > + res = NEEDS_CHECKING; > + } > + } else > + res = 0; > } > if (res) { > if (res == NEEDS_CHECKING) { Applied, thanks.
diff --git a/libavformat/matroskadec.c b/libavformat/matroskadec.c index 1db7471440..caabfcf6ac 100644 --- a/libavformat/matroskadec.c +++ b/libavformat/matroskadec.c @@ -1256,13 +1256,23 @@ static int ebml_parse_elem(MatroskaDemuxContext *matroska, case EBML_STOP: return 1; default: - if (ffio_limit(pb, length) != length) { - // ffio_limit emits its own error message, - // so we don't have to. - return AVERROR(EIO); - } - res = avio_skip(pb, length); - res = res < 0 ? res : 0; + if (length) { + if (ffio_limit(pb, length) != length) { + // ffio_limit emits its own error message, + // so we don't have to. + return AVERROR(EIO); + } + if ((res = avio_skip(pb, length - 1)) >= 0) { + // avio_skip might take us past EOF. We check for this + // by skipping only length - 1 bytes, reading a byte and + // checking the error flags. This is done in order to check + // that the element has been properly skipped even when + // no filesize (that ffio_limit relies on) is available. + avio_r8(pb); + res = NEEDS_CHECKING; + } + } else + res = 0; } if (res) { if (res == NEEDS_CHECKING) {
Up until now, when an element was skipped, it was relied upon ffio_limit to make sure that there is enough data available to skip. ffio_limit itself relies upon the availability of the file's size. As this needn't be available, the check has been refined: First one byte less than intended is skipped, then another byte is read, followed by a check of the error flags. Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@gmail.com> --- libavformat/matroskadec.c | 24 +++++++++++++++++------- 1 file changed, 17 insertions(+), 7 deletions(-)