Date: Fri, 16 Mar 2018 15:38:22 -0700 From: Andrew Morton <akpm@...ux-foundation.org> To: Kees Cook <keescook@...omium.org> Cc: linux-kernel@...r.kernel.org, Segher Boessenkool <segher@...nel.crashing.org>, Thomas Gleixner <tglx@...utronix.de>, kernel-hardening@...ts.openwall.com Subject: Re: [PATCH v2] rslib: Remove VLAs by setting upper bound on nroots On Thu, 15 Mar 2018 15:59:19 -0700 Kees Cook <keescook@...omium.org> wrote: > Avoid stack VLAs by always allocating the upper bound of stack space > needed. The existing users of rslib appear to max out at 24 roots, > so use that as the upper bound until we have a reason to change it. > > Alternative considered: make init_rs() a true caller-instance and > pre-allocate the workspaces. This would possibly need locking and > a refactoring of the returned structure. > > Using kmalloc in this path doesn't look great, especially since at > least one caller (pstore) is sensitive to allocations during rslib > usage (it expects to run it during an Oops, for example). > >  https://lkml.org/lkml/2018/3/7/621 >  https://lkml.org/lkml/2018/3/9/838 Yeah, email  is rather important. This patch is a bit of a pig to review! The restriction to 24 roots might be a significant one, dunno. Perhaps we should just kmalloc these things? Otherwise, RS_MAX_ROOTS becomes part of the rs interface and should be documented and published in rslib.h?
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