Issue #7791 has been updated by rosenfeld (Rodrigo Rosenfeld Rosas).


trans (Thomas Sawyer) wrote:
> An error would be raised.

So you would have a successful DoS attack, right? Because the attacker would cause an exception after the symbols limit has been reached. After that, any request relying on #to_sym of an inexistent symbol would result in an exception being raised. And it is not uncommon that some web frameworks will use #to_sym sometimes I guess. Or even some action that hasn't be called yet would no longer work after the DoS attack. For instance, suppose you use some symbol for i18n in some action that hasn't been called yet before the DoS attack.
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Feature #7791: Let symbols be garbage collected
https://bugs.ruby-lang.org/issues/7791#change-35914

Author: rosenfeld (Rodrigo Rosenfeld Rosas)
Status: Feedback
Priority: Normal
Assignee: matz (Yukihiro Matsumoto)
Category: core
Target version: next minor


Lots of Denial-of-Service security vulnerabilities exploited in Ruby programs rely on symbols not being collected by garbage collector.

Ideally I'd prefer symbols and strings to behave exactly the same being just alternate ways of writing strings but I'll let this to another ticket.

This one simply asks for symbols to be allowed to be garbage collected when low on memory. Maybe one could set up some up-limit memory constraints dedicated to storing symbols. That way, the most accessed symbols would remain in that memory region and the least used ones would be reclaimed when the memory for symbols is over and a new symbol is created.

Or you could just allow symbols to be garbage collected any time. Any reasons why this would be a bad idea? Any performance benchmark demonstrating how using symbols instead of strings would make a real-world software perform much better?

Currently I only see symbols slowing down processing because people don't want to worry about it and will often use something like ActiveSupport Hash#with_indifferent_access or some other method to convert a string to symbol or vice versa...


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