From c6fbff135880056dfc5634d5aed4b71059e1b7ae Mon Sep 17 00:00:00 2001
From: Michael Niedermayer <michael@niedermayer.cc>
Date: Fri, 18 Nov 2016 17:00:30 +0100
Subject: [PATCH] avformat: Add max_streams option

This allows user apps to stop OOM due to excessive number of streams

Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>
(cherry picked from commit 1296f844955e513d19051c962656f829479d4fb9)
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>
---
 doc/formats.texi            | 4 ++++
 libavformat/avformat.h      | 7 +++++++
 libavformat/options_table.h | 1 +
 libavformat/utils.c         | 2 +-
 4 files changed, 13 insertions(+), 1 deletion(-)

diff --git a/doc/formats.texi b/doc/formats.texi
index 617cda54a9..b62ca43dd7 100644
--- a/doc/formats.texi
+++ b/doc/formats.texi
@@ -205,6 +205,10 @@ For example to separate the fields with newlines and indention:
 ffprobe -dump_separator "
                           "  -i ~/videos/matrixbench_mpeg2.mpg
 @end example
+
+@item max_streams @var{integer} (@emph{input})
+Specifies the maximum number of streams. This can be used to reject files that
+would require too many resources due to a large number of streams.
 @end table
 
 @c man end FORMAT OPTIONS
diff --git a/libavformat/avformat.h b/libavformat/avformat.h
index a6694765b2..ba8c615b18 100644
--- a/libavformat/avformat.h
+++ b/libavformat/avformat.h
@@ -1822,6 +1822,13 @@ typedef struct AVFormatContext {
      * Demuxing: Set by user.
      */
     int (*open_cb)(struct AVFormatContext *s, AVIOContext **p, const char *url, int flags, const AVIOInterruptCB *int_cb, AVDictionary **options);
+
+    /**
+     * The maximum number of streams.
+     * - encoding: unused
+     * - decoding: set by user through AVOptions (NO direct access)
+     */
+    int max_streams;
 } AVFormatContext;
 
 int av_format_get_probe_score(const AVFormatContext *s);
diff --git a/libavformat/options_table.h b/libavformat/options_table.h
index 8f3c3100f7..10cd793ef1 100644
--- a/libavformat/options_table.h
+++ b/libavformat/options_table.h
@@ -109,6 +109,7 @@ static const AVOption avformat_options[] = {
 {"dump_separator", "set information dump field separator", OFFSET(dump_separator), AV_OPT_TYPE_STRING, {.str = ", "}, CHAR_MIN, CHAR_MAX, D|E},
 {"codec_whitelist", "List of decoders that are allowed to be used", OFFSET(codec_whitelist), AV_OPT_TYPE_STRING, { .str = NULL },  CHAR_MIN, CHAR_MAX, D },
 {"format_whitelist", "List of demuxers that are allowed to be used", OFFSET(format_whitelist), AV_OPT_TYPE_STRING, { .str = NULL },  CHAR_MIN, CHAR_MAX, D },
+{"max_streams", "maximum number of streams", OFFSET(max_streams), AV_OPT_TYPE_INT, { .i64 = INT_MAX }, 0, INT_MAX, D },
 {NULL},
 };
 
diff --git a/libavformat/utils.c b/libavformat/utils.c
index a705065879..4f159d6bcb 100644
--- a/libavformat/utils.c
+++ b/libavformat/utils.c
@@ -3764,7 +3764,7 @@ AVStream *avformat_new_stream(AVFormatContext *s, const AVCodec *c)
     int i;
     AVStream **streams;
 
-    if (s->nb_streams >= INT_MAX/sizeof(*streams))
+    if (s->nb_streams >= FFMIN(s->max_streams, INT_MAX/sizeof(*streams)))
         return NULL;
     streams = av_realloc_array(s->streams, s->nb_streams + 1, sizeof(*streams));
     if (!streams)