Date: Fri, 16 Mar 2018 23:25:43 -0700 From: Kees Cook <keescook@...omium.org> To: Andrew Morton <akpm@...ux-foundation.org> Cc: LKML <linux-kernel@...r.kernel.org>, Segher Boessenkool <segher@...nel.crashing.org>, Thomas Gleixner <tglx@...utronix.de>, Kernel Hardening <kernel-hardening@...ts.openwall.com> Subject: Re: [PATCH v2] rslib: Remove VLAs by setting upper bound on nroots On Fri, Mar 16, 2018 at 3:59 PM, Andrew Morton <akpm@...ux-foundation.org> wrote: > 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). > > Oh. > > Could we allocate the storage during init_rs(), attach it to `struct > rs_control'? No, because they're modified during decode, and struct rs_control is shared between users. :( Doing those changes is possible, but it requires a rather extensive analysis of callers, etc. Hence, the 24 ultimately. -Kees -- Kees Cook Pixel Security
Powered by blists - more mailing lists
Confused about mailing lists and their use? Read about mailing lists on Wikipedia and check out these guidelines on proper formatting of your messages.