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avcodec/exif: avoid allocation failure on empty EXIF metadata

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An EXIF IFD with 0 entries is legal, but does not contain metadata. We
should not attempt to allocate a struct with size zero in this case, as
this causes an allocation failure. Instead, we just leave the struct
empty.

Fixes: #20305.

Signed-off-by: Leo Izen <leo.izen@gmail.com>
This commit is contained in:
Leo Izen
2025-08-24 09:12:49 -04:00
parent 2398fddf6e
commit ef9fe0fe0b
1 changed files with 8 additions and 3 deletions
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libavcodec/exif.c
+8 -3
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@@ -552,6 +552,10 @@ static int exif_parse_ifd_list(void *logctx, GetByteContext *gb, int le,
ifd->count = entries;
av_log(logctx, AV_LOG_DEBUG, "entry count for IFD: %u\n", ifd->count);
/* empty IFD is technically legal but equivalent to no metadata present */
if (!ifd->count)
goto end;
if (av_size_mult(ifd->count, sizeof(*ifd->entries), &required_size) < 0)
return AVERROR(ENOMEM);
temp = av_fast_realloc(ifd->entries, &ifd->size, required_size);
@@ -571,6 +575,7 @@ static int exif_parse_ifd_list(void *logctx, GetByteContext *gb, int le,
return ret;
}
end:
/*
* at the end of an IFD is an pointer to the next IFD
* or zero if there are no more IFDs, which is usually the case
@@ -1009,7 +1014,7 @@ static int exif_get_entry(void *logctx, AVExifMetadata *ifd, uint16_t id, int de
{
int offset = 1;
if (!ifd || ifd->entries && !ifd->count || ifd->count && !ifd->entries || !value)
if (!ifd || ifd->count && !ifd->entries || !value)
return AVERROR(EINVAL);
for (size_t i = 0; i < ifd->count; i++) {
@@ -1043,7 +1048,7 @@ int av_exif_set_entry(void *logctx, AVExifMetadata *ifd, uint16_t id, enum AVTif
AVExifEntry *entry = NULL;
AVExifEntry src = { 0 };
if (!ifd || ifd->entries && !ifd->count || ifd->count && !ifd->entries
if (!ifd || ifd->count && !ifd->entries
|| ifd_lead && !ifd_offset || !ifd_lead && ifd_offset
|| !value || ifd->count == 0xFFFFu)
return AVERROR(EINVAL);
@@ -1089,7 +1094,7 @@ static int exif_remove_entry(void *logctx, AVExifMetadata *ifd, uint16_t id, int
int32_t index = -1;
int ret = 0;
if (!ifd || ifd->entries && !ifd->count || ifd->count && !ifd->entries)
if (!ifd || ifd->count && !ifd->entries)
return AVERROR(EINVAL);
for (size_t i = 0; i < ifd->count; i++) {