Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752774Ab3DKEIh (ORCPT ); Thu, 11 Apr 2013 00:08:37 -0400 Received: from ozlabs.org ([203.10.76.45]:44351 "EHLO ozlabs.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752475Ab3DKEIf (ORCPT ); Thu, 11 Apr 2013 00:08:35 -0400 From: Rusty Russell To: Chen Gang , Stephen Boyd Cc: Andrew Morton , "linux-kernel\@vger.kernel.org" Subject: Re: [PATCH] kernel: kallsyms: memory override issue, need check destination buffer length In-Reply-To: <51662AC7.1090004@asianux.com> References: <51662AC7.1090004@asianux.com> User-Agent: Notmuch/0.14 (http://notmuchmail.org) Emacs/23.4.1 (i686-pc-linux-gnu) Date: Thu, 11 Apr 2013 13:38:15 +0930 Message-ID: <87eheh4sls.fsf@rustcorp.com.au> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2613 Lines: 74 Chen Gang writes: > We don't export any symbols > 128 characters, but if we did then > kallsyms_expand_symbol() would overflow the buffer handed to it. > So we need check destination buffer length when copying. > > the related test: > if we define an EXPORT function which name more than 128. > will panic when call kallsyms_lookup_name by init_kprobes on booting. > after check the length (provide this patch), it is ok. > > Implementaion: > add additional destination buffer length parameter (maxlen) > if uncompressed string is too long (>= maxlen), it will be truncated. > not check the parameters whether valid, since it is a static function. > > > Signed-off-by: Chen Gang > Signed-off-by: Rusty Russell ??!!! I never signed this off! I've never seen it before! Minor comments below: > -static unsigned int kallsyms_expand_symbol(unsigned int off, char *result) > +static unsigned int kallsyms_expand_symbol(unsigned int off, > + char *result, int maxlen) 'size_t maxlen' would be more explicit. > { > int len, skipped_first = 0; > const u8 *tptr, *data; > + char *begin = result; > /* Get the compressed symbol length from the first symbol byte. */ > data = &kallsyms_names[off]; > @@ -113,14 +116,16 @@ static unsigned int kallsyms_expand_symbol(unsigned int off, char *result) > while (*tptr) { > if (skipped_first) { > - *result = *tptr; > - result++; > + *result++ = *tptr; > + if (result - begin == maxlen - 1) > + goto tail; You could just decrement maxlen instead, and handle maxlen == 0 at the same time: if (maxlen <= 1) goto tail; *result = *tptr; result++; maxlen--; > @@ -176,7 +181,7 @@ unsigned long kallsyms_lookup_name(const char *name) > unsigned int off; > for (i = 0, off = 0; i < kallsyms_num_syms; i++) { > - off = kallsyms_expand_symbol(off, namebuf); > + off = kallsyms_expand_symbol(off, namebuf, sizeof(namebuf)); > if (strcmp(namebuf, name) == 0) > return kallsyms_addresses[i]; I prefer to use ARRAY_SIZE(namebuf) instead of sizeof(namebuf). That way we break compile if the declaration is changed from an array to a pointer one day. Same for the others. Thanks, Rusty. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/