Bug 53267 – NULL pointer crash in TextIterator::handleTextBox()

• Component: CSS
• Status: RESOLVED FIXED

[Thomas Sepez]

The following test case triggers a crash (or an assert in the debug version):
}
<style>
 *:nth-child(2):first-letter {float: left;direction: rtl;
</style>


Error is:ASSERTION FAILED: i < size()
(../../JavaScriptCore/wtf/Vector.h:534 T& WTF::Vector<T, inlineCapacity>::at(size_t) [with T = WebCore::InlineTextBox*, long unsigned int inlineCapacity = 0ul])

Program received signal EXC_BAD_ACCESS, Could not access memory.
Reason: KERN_INVALID_ADDRESS at address: 0xbbadbeef
[Switching to process 19707]
0x026790c7 in WTF::Vector<WebCore::InlineTextBox*, 0ul>::at (this=0xb49b7b44, i=0) at Vector.h:534
534	            ASSERT(i < size());
(gdb) where
#0  0x026790c7 in WTF::Vector<WebCore::InlineTextBox*, 0ul>::at (this=0xb49b7b44, i=0) at Vector.h:534
#1  0x0267910c in WTF::Vector<WebCore::InlineTextBox*, 0ul>::operator[] (this=0xb49b7b44, i=0) at Vector.h:543
#2  0x0267514d in WebCore::TextIterator::handleTextBox (this=0xb49b7ad8) at /Volumes/MacintoshHD2/c1/src/third_party/WebKit/WebCore/WebCore.gyp/../editing/TextIterator.cpp:545
#3  0x02675a97 in WebCore::TextIterator::handleTextNode (this=0xb49b7ad8) at /Volumes/MacintoshHD2/c1/src/third_party/WebKit/WebCore/WebCore.gyp/../editing/TextIterator.cpp:526
#4  0x02675c72 in WebCore::TextIterator::advance (this=0xb49b7ad8) at /Volumes/MacintoshHD2/c1/src/third_party/WebKit/WebCore/WebCore.gyp/../editing/TextIterator.cpp:403
#5  0x02676c37 in WebCore::TextIterator::TextIterator (this=0xb49b7ad8, r=0x2ed1cb30, behavior=WebCore::TextIteratorDefaultBehavior) at /Volumes/MacintoshHD2/c1/src/third_party/WebKit/WebCore/WebCore.gyp/../editing/TextIterator.cpp:344
#6  0x01f34394 in WebKit::frameContentAsPlainText (maxChars=65535, frame=0xb863600, output=0xb49b7bb0) at /Volumes/MacintoshHD2/c1/src/third_party/WebKit/WebKit/chromium/src/WebFrameImpl.cpp:204
#7  0x01f346a7 in WebKit::WebFrameImpl::contentAsText (this=0xc0489f0, maxChars=65535) at /Volumes/MacintoshHD2/c1/src/third_party/WebKit/WebKit/chromium/src/WebFrameImpl.cpp:1701


Appears similar to http://trac.webkit.org/changeset/58153 ;  the same fix also needs to be applied a few lines lower where that logic is repeated.

[Thomas Sepez]

Created attachment 80378 [details]
Proposed patch to check for empty vector as above.

[Eric Seidel (no email)]

Comment on attachment 80378 [details]
Proposed patch to check for empty vector as above.

View in context: https://bugs.webkit.org/attachment.cgi?id=80378&action=review

Looks sane.

> Source/WebCore/editing/TextIterator.cpp:546
> +        InlineTextBox* firstTextBox = renderer->containsReversedText() ? (m_sortedTextBoxes.isEmpty() ? 0 : m_sortedTextBoxes[0]) : renderer->firstTextBox();

vector really wants a version of it's .at() call which can handle oversized indicies and return a defautl value.

[Eric Seidel (no email)]

Being our rtl guy, mitz might want to see this go by.

[WebKit Commit Bot]

Comment on attachment 80378 [details]
Proposed patch to check for empty vector as above.

Clearing flags on attachment: 80378

Committed r76987: <http://trac.webkit.org/changeset/76987>

[WebKit Commit Bot]

All reviewed patches have been landed.  Closing bug.