Am Montag, 10. November 2014, 22:05:18 schrieb Herbert Xu: Hi Herbert,
> On Sun, Nov 09, 2014 at 11:33:52PM +0100, Stephan Mueller wrote: > > while working on the AF_ALG interface, I saw no active zeroizations of > > memory that may hold sensitive data that is maintained outside the kernel > > crypto API cipher handles. I think the following memory segments fall > > under that > > category: > Are you talking about temporary data that we generate as part of > the processing? If so they should be zeroed by the entity that > generates them. I currently see that the IV buffer (owned by skcipher) and the message digest buffer (owned by hash) are not memset(0) before freeing them. I agree that both are not really sensitive data. But wouldn't it be prudent to memset(0) them nonetheless in the skcipher_sock_destruct and hash_sock_destruct functions, respectively? > > > However, I am failing to find the right spot to add a zeroization for the > > latter one, i.e. the code that handles the pages send in by the user or > > the > > pages that are returned by the crypto API. Initially I thought > > skcipher_pull_sgl is a good spot for the symmetric ciphers as it evicts > > the > > used pages out of the scope of the kernel crypto API. I added a > > clear_page(sg_page(sg+1)) as well as memset(sg_page(sg+1), 0, plen) right > > before the put_page call. All that I got in return was a BUG() from the > > memory management layer. > > I don't think I understand what exactly you're trying to zero. > Can you give an example? Apologies, my bad as I did not check get_user_pages_fast well enough. I see now that we operate on the pages in user space directly without copy_from_user that would imply a kernel-internal copy. Please disregard my comment. > > Thanks, -- Ciao Stephan -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
