Re: [FFmpeg-devel] [PATCH 2/5] lavu/dict: check for malloc failures some more

[Lukasz Marek]

On 12.12.2014 18:15, wm4 wrote:

This fix is rather messy because of AV_DICT_DONT_STRDUP_VAL. It's not
even clear how this should be handled. Maybe freeing the user's data on
failure would actually be ok.


const char* arg suggests this function should not free it, but dict 
would free it eventually so I agree freeing it should be OK, and 
convenient for a user.


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Re: [FFmpeg-devel] [PATCH 2/5] lavu/dict: check for malloc failures some more

[Michael Niedermayer]

On Fri, Dec 12, 2014 at 06:15:40PM +0100, wm4 wrote:
 This fix is rather messy because of AV_DICT_DONT_STRDUP_VAL. It's not
 even clear how this should be handled. Maybe freeing the user's data on
 failure would actually be ok.
 ---
  libavutil/dict.c | 6 ++
  1 file changed, 6 insertions(+)
 
 diff --git a/libavutil/dict.c b/libavutil/dict.c
 index a362de0..c4b97dc 100644
 --- a/libavutil/dict.c
 +++ b/libavutil/dict.c
 @@ -72,6 +72,7 @@ int av_dict_set(AVDictionary **pm, const char *key, const 
 char *value,
  AVDictionary *m = *pm;
  AVDictionaryEntry *tag = av_dict_get(m, key, NULL, flags);
  char *oldval = NULL;
 +void *tmp = NULL;
  
  if (!m)
  m = *pm = av_mallocz(sizeof(*m));
 @@ -104,6 +105,7 @@ int av_dict_set(AVDictionary **pm, const char *key, const 
 char *value,
  m-elems[m-count].key = av_strdup(key);
  if (!m-elems[m-count].key)
  goto err_out;
 +tmp = m-elems[m-count].key;
  if (flags  AV_DICT_DONT_STRDUP_VAL) {
  m-elems[m-count].value = (char*)(intptr_t)value;
  } else if (oldval  flags  AV_DICT_APPEND) {
 @@ -117,7 +119,10 @@ int av_dict_set(AVDictionary **pm, const char *key, 
 const char *value,
  m-elems[m-count].value = newval;
  } else
  m-elems[m-count].value = av_strdup(value);
 +if (!m-elems[m-count].value)
 +goto err_out;
  m-count++;
 +tmp = NULL;
  }
  if (!m-count) {
  av_free(m-elems);
 @@ -133,6 +138,7 @@ err_out:
  }
  if (flags  AV_DICT_DONT_STRDUP_KEY) av_free((void*)key);
  if (flags  AV_DICT_DONT_STRDUP_VAL) av_free((void*)value);
 +av_free(tmp);

this will/can lead to double frees

[...]
-- 
Michael GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

What does censorship reveal? It reveals fear. -- Julian Assange


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