idec_dec: fix 0 offset of NULL pointer
in RemapMemBuffer() and AppendToMemBuffer()
@@ -166,9 +166,11 @@ static int AppendToMemBuffer(WebPIDecoder* const idec,
VP8Decoder* const dec = (VP8Decoder*)idec->dec_;
MemBuffer* const mem = &idec->mem_;
const int need_compressed_alpha = NeedCompressedAlpha(idec);
- const uint8_t* const old_start = mem->buf_ + mem->start_;
+ const uint8_t* const old_start =
+ (mem->buf_ == NULL) ? NULL : mem->buf_ + mem->start_;
const uint8_t* const old_base =
need_compressed_alpha ? dec->alpha_data_ : old_start;
+ assert(mem->buf_ != NULL || mem->start_ == 0);
assert(mem->mode_ == MEM_MODE_APPEND);
if (data_size > MAX_CHUNK_PAYLOAD) {
// security safeguard: trying to allocate more than what the format
@@ -184,7 +186,7 @@ static int AppendToMemBuffer(WebPIDecoder* const idec,
uint8_t* const new_buf =
(uint8_t*)WebPSafeMalloc(extra_size, sizeof(*new_buf));
if (new_buf == NULL) return 0;
- memcpy(new_buf, old_base, current_size);
+ if (old_base != NULL) memcpy(new_buf, old_base, current_size);
WebPSafeFree(mem->buf_);
mem->buf_ = new_buf;
mem->buf_size_ = (size_t)extra_size;
@@ -192,6 +194,7 @@ static int AppendToMemBuffer(WebPIDecoder* const idec,
mem->end_ = current_size;
}
+ assert(mem->buf_ != NULL);
memcpy(mem->buf_ + mem->end_, data, data_size);
mem->end_ += data_size;
assert(mem->end_ <= mem->buf_size_);
@@ -204,7 +207,9 @@ static int RemapMemBuffer(WebPIDecoder* const idec,
const uint8_t* const data, size_t data_size) {
MemBuffer* const mem = &idec->mem_;
const uint8_t* const old_buf = mem->buf_;
- const uint8_t* const old_start = old_buf + mem->start_;
+ const uint8_t* const old_start =
+ (old_buf == NULL) ? NULL : old_buf + mem->start_;
+ assert(old_buf != NULL || mem->start_ == 0);
assert(mem->mode_ == MEM_MODE_MAP);
if (data_size < mem->buf_size_) return 0; // can't remap to a shorter buffer!
