From mboxrd@z Thu Jan 1 00:00:00 1970 Date: Fri, 16 Mar 2018 15:59:50 -0700 From: Andrew Morton Subject: Re: [PATCH v2] rslib: Remove VLAs by setting upper bound on nroots Message-Id: <20180316155950.35fda7c63ec59277ba504201@linux-foundation.org> In-Reply-To: <20180315225919.GA43806@beast> References: <20180315225919.GA43806@beast> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit To: Kees Cook Cc: linux-kernel@vger.kernel.org, Segher Boessenkool , Thomas Gleixner , kernel-hardening@lists.openwall.com List-ID: On Thu, 15 Mar 2018 15:59:19 -0700 Kees Cook 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'?