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[FFmpeg-devel] lavf/mov: Do not blindly allocate stts entries

Message ID CAB0OVGriQHHnViAm=G3vc4Jzgh3m6buM9g_kOSqRBNFJQ_kadQ@mail.gmail.com
State Superseded
Headers show

Commit Message

Carl Eugen Hoyos Dec. 31, 2017, 9:26 p.m. UTC 
2017-12-31 22:17 GMT+01:00 Michael Niedermayer <michael@niedermayer.cc>:
> On Sat, Dec 30, 2017 at 02:36:39PM +0100, Carl Eugen Hoyos wrote:
>> 2017-12-29 23:37 GMT+01:00 Carl Eugen Hoyos <ceffmpeg@gmail.com>:
>> > 2017-11-28 21:32 GMT+01:00 Michael Niedermayer <michael@niedermayer.cc>:
>> >> On Mon, Nov 27, 2017 at 05:24:14AM +0100, Carl Eugen Hoyos wrote:
>> >
>> >>>      for (i = 0; i < entries && !pb->eof_reached; i++) {
>> >>> -        int sample_duration;
>> >>> +        int sample_duration, ret;
>> >>>          unsigned int sample_count;
>> >>> +        if (i > sc->stts_count) {
>> >>> +            ret = av_reallocp_array(&sc->stts_data,
>> >>> +                                    FFMIN(sc->stts_count * 2LL, entries),
>> >>> +                                    sizeof(*sc->stts_data));
>> >>
>> >> this should use a variant of av_fast_realloc
>> >
>> > Do you prefer the new patch?
>> > The old variant here looks slightly saner to me.
>>
>> Attached is what you possibly had in mind.
>>
>> Please review, Carl Eugen
>
>>  mov.c |   13 +++++++++++--
>>  1 file changed, 11 insertions(+), 2 deletions(-)
>> cc7986179fe0ddc394457e8543d9ae907b49373c  0001-lavf-mov-Use-av_fast_realloc-in-mov_read_stts.patch
>> From f5fcd9ed1e5ce604c358a3787f1977277005ebb5 Mon Sep 17 00:00:00 2001
>> From: Carl Eugen Hoyos <ceffmpeg@gmail.com>
>> Date: Sat, 30 Dec 2017 14:34:41 +0100
>> Subject: [PATCH] lavf/mov: Use av_fast_realloc() in mov_read_stts().
>>
>> Avoids large allocations for short files with invalid stts entry.
>> Fixes bugzilla 1102.
>> ---
>>  libavformat/mov.c |   13 +++++++++++--
>>  1 file changed, 11 insertions(+), 2 deletions(-)
>>
>> diff --git a/libavformat/mov.c b/libavformat/mov.c
>> index 2064473..1e97652 100644
>> --- a/libavformat/mov.c
>> +++ b/libavformat/mov.c
>> @@ -2850,13 +2850,22 @@ static int mov_read_stts(MOVContext *c, AVIOContext *pb, MOVAtom atom)
>>          av_log(c->fc, AV_LOG_WARNING, "Duplicated STTS atom\n");
>>      av_free(sc->stts_data);
>>      sc->stts_count = 0;
>> -    sc->stts_data = av_malloc_array(entries, sizeof(*sc->stts_data));
>> -    if (!sc->stts_data)
>> +    if (entries >= INT_MAX / sizeof(*sc->stts_data))
>>          return AVERROR(ENOMEM);
>
> this leaves a stale pointer on error in sc->stts_data

New patch attached.

Thank you, Carl Eugen
diff mbox

Patch

From 42fc4aabccb5b5da0db2fd312187d90b303e96f7 Mon Sep 17 00:00:00 2001
From: Carl Eugen Hoyos <ceffmpeg@gmail.com>
Date: Sun, 31 Dec 2017 22:25:29 +0100
Subject: [PATCH] lavf/mov: Use av_fast_realloc() in mov_read_stts().

Avoids large allocations for short files with invalid stts entry.
Fixes bugzilla 1102.
---
 libavformat/mov.c |   15 ++++++++++++---
 1 file changed, 12 insertions(+), 3 deletions(-)

diff --git a/libavformat/mov.c b/libavformat/mov.c
index 2064473..ee86c65 100644
--- a/libavformat/mov.c
+++ b/libavformat/mov.c
@@ -2848,15 +2848,24 @@  static int mov_read_stts(MOVContext *c, AVIOContext *pb, MOVAtom atom)
 
     if (sc->stts_data)
         av_log(c->fc, AV_LOG_WARNING, "Duplicated STTS atom\n");
-    av_free(sc->stts_data);
+    av_freep(&sc->stts_data);
     sc->stts_count = 0;
-    sc->stts_data = av_malloc_array(entries, sizeof(*sc->stts_data));
-    if (!sc->stts_data)
+    if (entries >= INT_MAX / sizeof(*sc->stts_data))
         return AVERROR(ENOMEM);
 
     for (i = 0; i < entries && !pb->eof_reached; i++) {
         int sample_duration;
         unsigned int sample_count;
+        unsigned alloc_size = 0, min_entries = FFMIN(FFMAX(i, 1024 * 1024), entries);
+        MOVStts *stts_data = av_fast_realloc(sc->stts_data, &alloc_size,
+                                             min_entries * sizeof(*sc->stts_data));
+        if (!stts_data) {
+            av_freep(&sc->stts_data);
+            sc->stts_count = 0;
+            return AVERROR(ENOMEM);
+        }
+        sc->stts_count = min_entries;
+        sc->stts_data = stts_data;
 
         sample_count=avio_rb32(pb);
         sample_duration = avio_rb32(pb);
-- 
1.7.10.4