Use fixed size buffer for RLE bmps

An RLE bmp reports how many bytes it should contain. This number may be
incorrect, or it may be a very large number. Previously, we buffered
all bytes in a single allocation. Instead, use a fixed size buffer and
only read what fits into the buffer. We already have code to refill the
buffer if there is more data, so rely on that to keep reading.

Choose an arbitrary size for the buffer. It is larger than the maximum
possible number of bytes we need to read at once.

Add a test with a test image that reports a very large number for
the number of bytes it should contain. With the old method, we would
allocate 4 gigs of memory to decode this image, which is unnecessary
and may result in OOM.

BUG=b/33251605

Change-Id: I6d66eace626002725f62237617140cab99ce42f3
Reviewed-on: https://skia-review.googlesource.com/7028
Commit-Queue: Leon Scroggins <scroggo@google.com>
Reviewed-by: Matt Sarett <msarett@google.com>

1 files changed, 1 insertions, 2 deletions

diff --git a/src/codec/SkBmpCodec.cpp b/src/codec/SkBmpCodec.cpp
index 83ba21b0d6..66ad0caa2b 100644
--- a/src/codec/SkBmpCodec.cpp
+++ b/src/codec/SkBmpCodec.cpp
@@ -549,7 +549,6 @@ bool SkBmpCodec::ReadHeader(SkStream* stream, bool inIco, SkCodec** codecOut) {
                 SkCodecPrintf("Error: RLE requires valid input size.\n");
                 return false;
             }
-            const size_t RLEBytes = totalBytes - offset;
 
             // Bmp-in-Ico must be standard mode
             // When inIco is true, this line cannot be reached, since we
@@ -565,7 +564,7 @@ bool SkBmpCodec::ReadHeader(SkStream* stream, bool inIco, SkCodec** codecOut) {
                 const SkEncodedInfo info = SkEncodedInfo::Make(SkEncodedInfo::kBGRA_Color,
                         SkEncodedInfo::kBinary_Alpha, 8);
                 *codecOut = new SkBmpRLECodec(width, height, info, stream, bitsPerPixel, numColors,
-                        bytesPerColor, offset - bytesRead, rowOrder, RLEBytes);
+                        bytesPerColor, offset - bytesRead, rowOrder);
             }
             return true;
         }