Adding upstream version 115.7.0esr.upstream/115.7.0esr

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 169 insertions, 0 deletions

diff --git a/layout/svg/AutoReferenceChainGuard.h b/layout/svg/AutoReferenceChainGuard.h
new file mode 100644
index 0000000000..c25ba0ea70
--- /dev/null
+++ b/layout/svg/AutoReferenceChainGuard.h
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+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef LAYOUT_SVG_AUTOREFERENCECHAINGUARD_H_
+#define LAYOUT_SVG_AUTOREFERENCECHAINGUARD_H_
+
+#include "Element.h"
+#include "mozilla/Assertions.h"
+#include "mozilla/Attributes.h"
+#include "mozilla/ReentrancyGuard.h"
+#include "mozilla/Likely.h"
+#include "nsDebug.h"
+#include "mozilla/dom/Document.h"
+#include "nsIFrame.h"
+
+namespace mozilla {
+
+/**
+ * This helper class helps us to protect against two related issues that can
+ * occur in SVG content: reference loops, and reference chains that we deem to
+ * be too long.
+ *
+ * Some SVG effects can reference another effect of the same type to produce
+ * a chain of effects to be applied (e.g. clipPath), while in other cases it is
+ * possible that while processing an effect of a certain type another effect
+ * of the same type may be encountered indirectly (e.g. pattern).  In order to
+ * avoid stack overflow crashes and performance issues we need to impose an
+ * arbitrary limit on the length of the reference chains that SVG content may
+ * try to create.  (Some SVG authoring tools have been known to create absurdly
+ * long reference chains.  For example, bug 1253590 details a case where Adobe
+ * Illustrator was used to created an SVG with a chain of 5000 clip paths which
+ * could cause us to run out of stack space and crash.)
+ *
+ * This class is intended to be used with the nsIFrame's of SVG effects that
+ * may involve reference chains.  To use it add a boolean member, something
+ * like this:
+ *
+ *   // Flag used to indicate whether a methods that may reenter due to
+ *   // following a reference to another instance is currently executing.
+ *   bool mIsBeingProcessed;
+ *
+ * Make sure to initialize the member to false in the class' constructons.
+ *
+ * Then add the following to the top of any methods that may be reentered due
+ * to following a reference:
+ *
+ *   static int16_t sRefChainLengthCounter = AutoReferenceChainGuard::noChain;
+ *
+ *   AutoReferenceChainGuard refChainGuard(this, &mIsBeingProcessed,
+ *                                         &sRefChainLengthCounter);
+ *   if (MOZ_UNLIKELY(!refChainGuard.Reference())) {
+ *     return; // Break reference chain
+ *   }
+ *
+ * Note that mIsBeingProcessed and sRefChainLengthCounter should never be used
+ * by the frame except when it initialize them as indicated above.
+ */
+class MOZ_RAII AutoReferenceChainGuard {
+  static const int16_t sDefaultMaxChainLength = 10;  // arbitrary length
+
+ public:
+  static const int16_t noChain = -2;
+
+  /**
+   * @param aFrame The frame for an effect that may involve a reference chain.
+   * @param aFrameInUse The member variable on aFrame that is used to indicate
+   *   whether one of aFrame's methods that may involve following a reference
+   *   to another effect of the same type is currently being executed.
+   * @param aChainCounter A static variable in the method in which this class
+   *   is instantiated that is used to keep track of how many times the method
+   *   is reentered (and thus how long the a reference chain is).
+   * @param aMaxChainLength The maximum number of links that are allowed in
+   *   a reference chain.
+   */
+  AutoReferenceChainGuard(nsIFrame* aFrame, bool* aFrameInUse,
+                          int16_t* aChainCounter,
+                          int16_t aMaxChainLength = sDefaultMaxChainLength)
+      : mFrame(aFrame),
+        mFrameInUse(aFrameInUse),
+        mChainCounter(aChainCounter),
+        mMaxChainLength(aMaxChainLength),
+        mBrokeReference(false) {
+    MOZ_ASSERT(aFrame && aFrameInUse && aChainCounter);
+    MOZ_ASSERT(aMaxChainLength > 0);
+    MOZ_ASSERT(*aChainCounter == noChain ||
+               (*aChainCounter >= 0 && *aChainCounter < aMaxChainLength));
+  }
+
+  ~AutoReferenceChainGuard() {
+    if (mBrokeReference) {
+      // We didn't change mFrameInUse or mChainCounter
+      return;
+    }
+
+    *mFrameInUse = false;
+
+    // If we fail this assert then there were more destructor calls than
+    // Reference() calls (a consumer forgot to to call Reference()), or else
+    // someone messed with the variable pointed to by mChainCounter.
+    MOZ_ASSERT(*mChainCounter < mMaxChainLength);
+
+    (*mChainCounter)++;
+
+    if (*mChainCounter == mMaxChainLength) {
+      *mChainCounter = noChain;  // reset ready for use next time
+    }
+  }
+
+  /**
+   * Returns true on success (no reference loop/reference chain length is
+   * within the specified limits), else returns false on failure (there is a
+   * reference loop/the reference chain has exceeded the specified limits).
+   * If it returns false then an error message will be reported to the DevTools
+   * console (only once).
+   */
+  [[nodiscard]] bool Reference() {
+    if (MOZ_UNLIKELY(*mFrameInUse)) {
+      mBrokeReference = true;
+      ReportErrorToConsole();
+      return false;
+    }
+
+    if (*mChainCounter == noChain) {
+      // Initialize - we start at aMaxChainLength and decrement towards zero.
+      *mChainCounter = mMaxChainLength;
+    } else {
+      // If we fail this assertion then either a consumer failed to break a
+      // reference loop/chain, or else they called Reference() more than once
+      MOZ_ASSERT(*mChainCounter >= 0);
+
+      if (MOZ_UNLIKELY(*mChainCounter < 1)) {
+        mBrokeReference = true;
+        ReportErrorToConsole();
+        return false;
+      }
+    }
+
+    // We only set these once we know we're returning true.
+    *mFrameInUse = true;
+    (*mChainCounter)--;
+
+    return true;
+  }
+
+ private:
+  void ReportErrorToConsole() {
+    AutoTArray<nsString, 2> params;
+    dom::Element* element = mFrame->GetContent()->AsElement();
+    element->GetTagName(*params.AppendElement());
+    element->GetId(*params.AppendElement());
+    auto doc = mFrame->GetContent()->OwnerDoc();
+    auto warning = *mFrameInUse ? dom::Document::eSVGRefLoop
+                                : dom::Document::eSVGRefChainLengthExceeded;
+    doc->WarnOnceAbout(warning, /* asError */ true, params);
+  }
+
+  nsIFrame* mFrame;
+  bool* mFrameInUse;
+  int16_t* mChainCounter;
+  const int16_t mMaxChainLength;
+  bool mBrokeReference;
+};
+
+}  // namespace mozilla
+
+#endif  // LAYOUT_SVG_AUTOREFERENCECHAINGUARD_H_