Avoid crashing when SetText is called with a 2GB large string #990
Conversation
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
The expression ``const int newAllocated = cap * 2;`` easily causes
overflow, as soon as the input is 1.0 GiB. This goes unnoticed because
release builds of tinyxml2 do not have active assertions.
The change in commit 9.0.0-20-g8fd6cc6 did not do anything useful;
the signed multiplication overflow (and thus undefined behavior)
still occurs.
Using ``int`` in this class is really archaic, because it limits the
class to a gigabyte even on 64-bit platforms.
The multiplication overflow check also needs to include sizeof(T),
otherwise you can run into unsigned multiplication overflow (defined,
but undesirable) in the memcpy() call.
testcase:
int main()
{
tinyxml2::XMLDocument doc;
doc.InsertEndChild(doc.NewDeclaration());
auto root = doc.NewElement("root");
size_t sz = 0x80000001;
auto blank = new char[sz];
memset(blank, ' ', sz);
blank[sz-1]='\0';
root->SetText(blank);
doc.InsertEndChild(root);
tinyxml2::XMLPrinter printer(nullptr);
doc.Print(&printer);
}
|
Nice, thanks |
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
Add this suggestion to a batch that can be applied as a single commit.
This suggestion is invalid because no changes were made to the code.
Suggestions cannot be applied while the pull request is closed.
Suggestions cannot be applied while viewing a subset of changes.
Only one suggestion per line can be applied in a batch.
Add this suggestion to a batch that can be applied as a single commit.
Applying suggestions on deleted lines is not supported.
You must change the existing code in this line in order to create a valid suggestion.
Outdated suggestions cannot be applied.
This suggestion has been applied or marked resolved.
Suggestions cannot be applied from pending reviews.
Suggestions cannot be applied on multi-line comments.
Suggestions cannot be applied while the pull request is queued to merge.
Suggestion cannot be applied right now. Please check back later.
The expression
const int newAllocated = cap * 2;easily causes overflow, as soon as the input is 1.0 GiB. This goes unnoticed because release builds of tinyxml2 do not have active assertions.The change in commit 9.0.0-20-g8fd6cc6 did not do anything useful; the signed multiplication overflow (and thus undefined behavior) still occurs.
Using
intin this class is really archaic, because it limits the class to a gigabyte even on 64-bit platforms.The multiplication overflow check also needs to include sizeof(T), otherwise you can run into unsigned multiplication overflow (defined, but undesirable) in the memcpy() call.
testcase: