Re: [FFmpeg-devel] [PATCH 1/6] avcodec/tiff: Fix handling of av_strdup() failures

[Stefano Sabatini <stefasab@gmail.com>]

On date Sunday 2024-03-10 15:12:16 +0100, Andreas Rheinhardt wrote:
> For unknown geokey values, get_geokey_val() returns
> "Unknown-%d" with val being used for %d. This string
> is allocated and therefore all the known geokey values
> (static strings) are strdup'ed. In case this fails
> it is either ignored or treated as "Unknown-%d".
> (Furthermore it is possible to call av_strdup(NULL),
> although this is not documented to be legal.)
> 
> This commit changes this by only returning the static strings
> in get_geokey_val(); the unknown handling and strdup'ing
> is moved out of it.
> 
> Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@outlook.com>
> ---
>  libavcodec/tiff.c | 35 ++++++++++++++++-------------------
>  1 file changed, 16 insertions(+), 19 deletions(-)
> 
> diff --git a/libavcodec/tiff.c b/libavcodec/tiff.c
> index cb4d378753..4c7460cf41 100644
> --- a/libavcodec/tiff.c
> +++ b/libavcodec/tiff.c
> @@ -36,6 +36,7 @@
>  #include <float.h>
>  
>  #include "libavutil/attributes.h"
> +#include "libavutil/avstring.h"
>  #include "libavutil/error.h"
>  #include "libavutil/intreadwrite.h"
>  #include "libavutil/opt.h"
> @@ -179,19 +180,17 @@ static const char *search_keyval(const TiffGeoTagKeyName *keys, int n, int id)
>      return NULL;
>  }
>  
> -static char *get_geokey_val(int key, int val)
> +static const char *get_geokey_val(int key, uint16_t val)
>  {
> -    char *ap;
> -
>      if (val == TIFF_GEO_KEY_UNDEFINED)
> -        return av_strdup("undefined");
> +        return "undefined";
>      if (val == TIFF_GEO_KEY_USER_DEFINED)
> -        return av_strdup("User-Defined");
> +        return "User-Defined";
>  
>  #define RET_GEOKEY_VAL(TYPE, array)\
>      if (val >= TIFF_##TYPE##_OFFSET &&\
>          val - TIFF_##TYPE##_OFFSET < FF_ARRAY_ELEMS(tiff_##array##_codes))\
> -        return av_strdup(tiff_##array##_codes[val - TIFF_##TYPE##_OFFSET]);
> +        return tiff_##array##_codes[val - TIFF_##TYPE##_OFFSET];
>  
>      switch (key) {
>      case TIFF_GT_MODEL_TYPE_GEOKEY:
> @@ -224,13 +223,9 @@ static char *get_geokey_val(int key, int val)
>          RET_GEOKEY_VAL(PRIME_MERIDIAN, prime_meridian);
>          break;
>      case TIFF_PROJECTED_CS_TYPE_GEOKEY:
> -        ap = av_strdup(search_keyval(tiff_proj_cs_type_codes, FF_ARRAY_ELEMS(tiff_proj_cs_type_codes), val));
> -        if(ap) return ap;
> -        break;
> +        return search_keyval(tiff_proj_cs_type_codes, FF_ARRAY_ELEMS(tiff_proj_cs_type_codes), val);
>      case TIFF_PROJECTION_GEOKEY:
> -        ap = av_strdup(search_keyval(tiff_projection_codes, FF_ARRAY_ELEMS(tiff_projection_codes), val));
> -        if(ap) return ap;
> -        break;
> +        return search_keyval(tiff_projection_codes, FF_ARRAY_ELEMS(tiff_projection_codes), val);
>      case TIFF_PROJ_COORD_TRANS_GEOKEY:
>          RET_GEOKEY_VAL(COORD_TRANS, coord_trans);
>          break;
> @@ -241,10 +236,7 @@ static char *get_geokey_val(int key, int val)
>  
>      }
>  
> -    ap = av_malloc(14);
> -    if (ap)
> -        snprintf(ap, 14, "Unknown-%d", val);
> -    return ap;
> +    return NULL;
>  }
>  
>  static char *doubles2str(double *dp, int count, const char *sep)
> @@ -1634,9 +1626,14 @@ static int tiff_decode_tag(TiffContext *s, AVFrame *frame)
>              s->geotags[i].type   = ff_tget_short(&s->gb, s->le);
>              s->geotags[i].count  = ff_tget_short(&s->gb, s->le);
>  
> -            if (!s->geotags[i].type)
> -                s->geotags[i].val  = get_geokey_val(s->geotags[i].key, ff_tget_short(&s->gb, s->le));
> -            else
> +            if (!s->geotags[i].type) {
> +                uint16_t val    = ff_tget_short(&s->gb, s->le);
> +                const char *str = get_geokey_val(s->geotags[i].key, val);
> +
> +                s->geotags[i].val = str ? av_strdup(str) : av_asprintf("Unknown-%u", val);
> +                if (!s->geotags[i].val)
> +                    return AVERROR(ENOMEM);
> +            } else
>                  s->geotags[i].offset = ff_tget_short(&s->gb, s->le);

nit++: you migth factorize the ff_tget_short call

>          }
>          break;

LGTM.
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