Return nullptr when ReadBuffer becomes invalid

This especially helps in SkDrawLooper because we can bail out early
instead of looping for a potentially long time, e.g. when fuzzed
input says count is a large number.

This also cleans up validate in a few spots, and adds validateCanReadN
as a helper function.

Bug: skia:7937
Change-Id: Ic5eff357c8cadc91eeafc6e39c78c570ba74df2f
Reviewed-on: https://skia-review.googlesource.com/128847
Commit-Queue: Kevin Lubick <kjlubick@google.com>
Commit-Queue: Mike Klein <mtklein@google.com>
Reviewed-by: Mike Klein <mtklein@google.com>
Reviewed-by: Florin Malita <fmalita@chromium.org>

4 files changed, 10 insertions, 1 deletions

diff --git a/src/effects/SkArithmeticImageFilter.cpp b/src/effects/SkArithmeticImageFilter.cpp
index 24c95c82ce..984ed80a19 100644
--- a/src/effects/SkArithmeticImageFilter.cpp
+++ b/src/effects/SkArithmeticImageFilter.cpp
@@ -86,6 +86,9 @@ sk_sp<SkFlattenable> ArithmeticImageFilterImpl::CreateProc(SkReadBuffer& buffer)
         k[i] = buffer.readScalar();
     }
     const bool enforcePMColor = buffer.readBool();
+    if (!buffer.isValid()) {
+        return nullptr;
+    }
     return SkArithmeticImageFilter::Make(k[0], k[1], k[2], k[3], enforcePMColor, common.getInput(0),
                                          common.getInput(1), &common.cropRect());
 }
diff --git a/src/effects/SkDashPathEffect.cpp b/src/effects/SkDashPathEffect.cpp
index 4cb98b3ad8..cdadcf907d 100644
--- a/src/effects/SkDashPathEffect.cpp
+++ b/src/effects/SkDashPathEffect.cpp
@@ -369,7 +369,7 @@ sk_sp<SkFlattenable> SkDashImpl::CreateProc(SkReadBuffer& buffer) {
     uint32_t count = buffer.getArrayCount();
 
     // Don't allocate gigantic buffers if there's not data for them.
-    if (count > buffer.size() / sizeof(SkScalar)) {
+    if (!buffer.validateCanReadN<SkScalar>(count)) {
         return nullptr;
     }
 
diff --git a/src/effects/SkLayerDrawLooper.cpp b/src/effects/SkLayerDrawLooper.cpp
index 6a8254d894..db61e08c4f 100644
--- a/src/effects/SkLayerDrawLooper.cpp
+++ b/src/effects/SkLayerDrawLooper.cpp
@@ -272,6 +272,9 @@ sk_sp<SkFlattenable> SkLayerDrawLooper::CreateProc(SkReadBuffer& buffer) {
         buffer.readPoint(&info.fOffset);
         info.fPostTranslate = buffer.readBool();
         buffer.readPaint(builder.addLayerOnTop(info));
+        if (!buffer.isValid()) {
+            return nullptr;
+        }
     }
     return builder.detach();
 }
diff --git a/src/effects/SkXfermodeImageFilter.cpp b/src/effects/SkXfermodeImageFilter.cpp
index 1c670fbe0b..587784a391 100644
--- a/src/effects/SkXfermodeImageFilter.cpp
+++ b/src/effects/SkXfermodeImageFilter.cpp
@@ -375,6 +375,9 @@ sk_sp<SkFlattenable> SkXfermodeImageFilter_Base::LegacyArithmeticCreateProc(SkRe
         k[i] = buffer.readScalar();
     }
     const bool enforcePMColor = buffer.readBool();
+    if (!buffer.isValid()) {
+        return nullptr;
+    }
     return SkArithmeticImageFilter::Make(k[0], k[1], k[2], k[3], enforcePMColor, common.getInput(0),
                                          common.getInput(1), &common.cropRect());
 }