bug 8014477 Race in String.contentEquals (original) (raw)

Peter Levart peter.levart at gmail.com
Tue May 14 11:34:16 UTC 2013

On 05/14/2013 01:17 PM, David Holmes wrote:

Thanks Peter this looks good to me.

One minor thing please set the correct copyright year in the test, it should just be Copyright (c) 2013, Oracle ...

Ok, fixed:

http://cr.openjdk.java.net/~plevart/jdk8-tl/String.contentEquals/webrev.04/

I couldn't get the test to actually fail, but I can see that it could.

Hm, do you have a multi-core chip? On my computer (i7 CPU) it fails immediately and always. You could try varying the number of concurrent threads and or the time to wait for exception to be thrown...

David On 14/05/2013 9:04 PM, Peter Levart wrote: Ok, here's the corrected fix:

http://cr.openjdk.java.net/~plevart/jdk8-tl/String.contentEquals/webrev.03/

I also added a reproducer for the bug. Regards, peter On 05/14/2013 07:53 AM, Peter Levart wrote: Right, sb.length() should be used. I will correct that as soon as I get to the keyboard. Regards, Peter On May 14, 2013 7:22 AM, "David Holmes" <david.holmes at oracle.com_ _<mailto:david.holmes at oracle.com>> wrote: Thanks Peter! I've filed 8014477 Race condition in String.contentEquals when comparing with StringBuffer On 14/05/2013 8:34 AM, Peter Levart wrote: On 05/14/2013 12:09 AM, Peter Levart wrote: I noticed a synchronization bug in String.contentEquals method. If called with a StringBuffer argument while concurrent thread is modifying the StringBuffer, the method can either throw ArrayIndexOutOfBoundsException or return true even though the content of the StringBuffer has never been the same as the String's. Here's a proposed patch: http://cr.openjdk.java.net/~plevart/jdk8-tl/String.contentEquals/webrev.01/ <http://cr.openjdk.java.net/%7Eplevart/jdk8-tl/String.contentEquals/webrev.01/> Regards, Peter

Or even better (with some code clean-up): http://cr.openjdk.java.net/~plevart/jdk8-tl/String.contentEquals/webrev.02/ <http://cr.openjdk.java.net/%7Eplevart/jdk8-tl/String.contentEquals/webrev.02/> This part is not correct I believe: 1010 private boolean nonSyncContentEquals(AbstractStringBuilder sb) { 1011 char v1[] = value; 1012 char v2[] = sb.getValue(); 1013 int n = v1.length; 1014 if (n != v2.length) { 1015 return false; 1016 } v2 can be larger than v1 if v2 is not being fully used (ie count < length). David -----

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