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[188.192.142.35]) by smtp.gmail.com with ESMTPSA id q15sm16713082wmq.0.2019.11.16.23.35.20 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sat, 16 Nov 2019 23:35:20 -0800 (PST) From: Andreas Rheinhardt To: ffmpeg-devel@ffmpeg.org Date: Sun, 17 Nov 2019 08:34:36 +0100 Message-Id: <20191117073440.22718-3-andreas.rheinhardt@gmail.com> X-Mailer: git-send-email 2.20.1 In-Reply-To: <20191117073440.22718-1-andreas.rheinhardt@gmail.com> References: <20191117073440.22718-1-andreas.rheinhardt@gmail.com> MIME-Version: 1.0 Subject: [FFmpeg-devel] [PATCH v2 2/6] avcodec/cbs: Fix potential overflow X-BeenThere: ffmpeg-devel@ffmpeg.org X-Mailman-Version: 2.1.20 Precedence: list List-Id: FFmpeg development discussions and patches List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Reply-To: FFmpeg development discussions and patches Cc: Andreas Rheinhardt Errors-To: ffmpeg-devel-bounces@ffmpeg.org Sender: "ffmpeg-devel" The number of bits in a PutBitContext must fit into an int, yet nothing guaranteed the size argument cbs_write_unit_data() uses in init_put_bits() to be in the range 0..INT_MAX / 8. This has been changed. Furthermore, the check 8 * data_size > data_bit_start that there is data beyond the initial padding when writing mpeg2 or H.264/5 slices could also overflow, so divide it by 8 to get an equivalent check without this problem. Signed-off-by: Andreas Rheinhardt --- libavcodec/cbs.c | 4 +++- libavcodec/cbs_h2645.c | 2 +- libavcodec/cbs_mpeg2.c | 2 +- 3 files changed, 5 insertions(+), 3 deletions(-) diff --git a/libavcodec/cbs.c b/libavcodec/cbs.c index ab3eadb534..0badb192d9 100644 --- a/libavcodec/cbs.c +++ b/libavcodec/cbs.c @@ -309,7 +309,9 @@ static int cbs_write_unit_data(CodedBitstreamContext *ctx, if (ret < 0) { if (ret == AVERROR(ENOSPC)) { // Overflow. - ctx->write_buffer_size *= 2; + if (ctx->write_buffer_size == INT_MAX / 8) + return AVERROR(ENOMEM); + ctx->write_buffer_size = FFMIN(2 * ctx->write_buffer_size, INT_MAX / 8); goto reallocate_and_try_again; } // Write failed for some other reason. diff --git a/libavcodec/cbs_h2645.c b/libavcodec/cbs_h2645.c index 923f77dcb4..88fa0029cd 100644 --- a/libavcodec/cbs_h2645.c +++ b/libavcodec/cbs_h2645.c @@ -1101,7 +1101,7 @@ static int cbs_h2645_write_slice_data(CodedBitstreamContext *ctx, const uint8_t *pos = data + data_bit_start / 8; av_assert0(data_bit_start >= 0 && - 8 * data_size > data_bit_start); + data_size > data_bit_start / 8); if (data_size * 8 + 8 > put_bits_left(pbc)) return AVERROR(ENOSPC); diff --git a/libavcodec/cbs_mpeg2.c b/libavcodec/cbs_mpeg2.c index a9cc4a4cf8..13d871cc89 100644 --- a/libavcodec/cbs_mpeg2.c +++ b/libavcodec/cbs_mpeg2.c @@ -337,7 +337,7 @@ static int cbs_mpeg2_write_slice(CodedBitstreamContext *ctx, uint8_t *pos = slice->data + slice->data_bit_start / 8; av_assert0(slice->data_bit_start >= 0 && - 8 * slice->data_size > slice->data_bit_start); + slice->data_size > slice->data_bit_start / 8); if (slice->data_size * 8 + 8 > put_bits_left(pbc)) return AVERROR(ENOSPC);