On Fri, Mar 16, 2018 at 3:59 PM, Andrew Morton <a...@linux-foundation.org> wrote: > On Thu, 15 Mar 2018 15:59:19 -0700 Kees Cook <keesc...@chromium.org> wrote: > >> Avoid stack VLAs[1] by always allocating the upper bound of stack space >> needed. The existing users of rslib appear to max out at 24 roots[2], >> 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