Date: Tue, 23 Oct 2018 00:22:28 +0000 From: Ramon de C Valle <rcvalle@...e.com> To: Andrew Sandoval <ASandoval@...root.com>, "oss-security@...ts.openwall.com" <oss-security@...ts.openwall.com> Subject: Re: GCC Compiler Induced Vulnerability - affects programs compiled with GCC 7 and 8 containing nested functions > This is already public because oss-security is a public mailing list. > > Most GNU/Linux distributions ensure that only very special binaries > (such as some versions of the Ada compiler) enable executable stacks. > In our experience, if the toolchain produces a binary that requests an > executable stack, it is more likely due to manually written assembler > files without the required stack executability markup section, and not > due to nested C functions whose address escapes. Without scanning built > binaries for these discrepancies, such cases could easily be missed. > > Please also note that an executable stack is not a vulnerability itself, > and it is not directly exploitable. (The same applies to the lack of > Intel CET support in binaries.) While I agree with that I still think that this extension (or its name) is misleading, see https://lkml.org/lkml/2012/1/9/138. The PF_X flag set in the PT_GNU_STACK segment header or the absence of the PT_GNU_STACK segment header can result in an application unnoticeably having not only the stack, but also all readable virtual memory mappings also executable. Ramon de C Valle
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