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Re: [PATCH] x86-64 memcmp: Use unsigned Jcc instructions on size
- From: Florian Weimer <fweimer at redhat dot com>
- To: "H.J. Lu" <hjl dot tools at gmail dot com>
- Cc: libc-alpha at sourceware dot org
- Date: Sat, 02 Feb 2019 15:56:57 +0100
- Subject: Re: [PATCH] x86-64 memcmp: Use unsigned Jcc instructions on size
- References: <firstname.lastname@example.org>
* H. J. Lu:
> Since the size argument is unsigned. we should use unsigned Jcc
> instructions, instead of signed to check size.
> Tested on x86-64 and x32, with and without --disable-multi-arch.
Does this impact x86-64 at all (technically), consider that an object
size larger than SSIZE_MAX would be undefined anyway?
It seems that on x32, it can give incorrect results if the sign bit on
the 64-bit register is set. In this sense, it is similar to
CVE-2019-6488 in impact, right? If we decide to treat this as a
security vulnerability, we need a new CVE ID because the version range
is different (bug 24155 was not fixed in the 2.29 release).