Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1759187Ab2KWKfm (ORCPT ); Fri, 23 Nov 2012 05:35:42 -0500 Received: from mail-ee0-f46.google.com ([74.125.83.46]:38536 "EHLO mail-ee0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752456Ab2KWKfi (ORCPT ); Fri, 23 Nov 2012 05:35:38 -0500 MIME-Version: 1.0 In-Reply-To: <20121122004213.695679336@linuxfoundation.org> References: <20121122004212.371862690@linuxfoundation.org> <20121122004213.695679336@linuxfoundation.org> Date: Fri, 23 Nov 2012 19:35:36 +0900 Message-ID: Subject: Re: [ 11/83] module: fix out-by-one error in kallsyms From: satoru takeuchi To: Greg Kroah-Hartman Cc: linux-kernel@vger.kernel.org, stable@vger.kernel.org, alan@lxorguk.ukuu.org.uk, Masaki Kimura , Rusty Russell Content-Type: text/plain; charset=ISO-8859-1 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 4754 Lines: 124 Hi, 2012/11/22 Greg Kroah-Hartman : > 3.6-stable review patch. If anyone has any objections, please let me know. > > ------------------ > > From: Rusty Russell > > commit 59ef28b1f14899b10d6b2682c7057ca00a9a3f47 upstream. > > Masaki found and patched a kallsyms issue: the last symbol in a > module's symtab wasn't transferred. This is because we manually copy > the zero'th entry (which is always empty) then copy the rest in a loop > starting at 1, though from src[0]. His fix was minimal, I prefer to > rewrite the loops in more standard form. > > There are two loops: one to get the size, and one to copy. Make these > identical: always count entry 0 and any defined symbol in an allocated > non-init section. > > This bug exists since the following commit was introduced. > module: reduce symbol table for loaded modules (v2) > commit: 4a4962263f07d14660849ec134ee42b63e95ea9a > > LKML: http://lkml.org/lkml/2012/10/24/27 > Reported-by: Masaki Kimura > Signed-off-by: Rusty Russell > Signed-off-by: Greg Kroah-Hartman > > --- > kernel/module.c | 27 ++++++++++++++++----------- > 1 file changed, 16 insertions(+), 11 deletions(-) > > --- a/kernel/module.c > +++ b/kernel/module.c > @@ -2273,12 +2273,17 @@ static void layout_symtab(struct module > src = (void *)info->hdr + symsect->sh_offset; > nsrc = symsect->sh_size / sizeof(*src); > > + /* strtab always starts with a nul, so offset 0 is the empty string. */ > + strtab_size = 1; > + I suspect above code sniped is not needed since the size of src[0](always 1) is counted at the following code("strtab_size += strlen(..) + 1;"). > /* Compute total space required for the core symbols' strtab. */ > - for (ndst = i = strtab_size = 1; i < nsrc; ++i, ++src) > - if (is_core_symbol(src, info->sechdrs, info->hdr->e_shnum)) { > - strtab_size += strlen(&info->strtab[src->st_name]) + 1; > + for (ndst = i = 0; i < nsrc; i++) { > + if (i == 0 || > + is_core_symbol(src+i, info->sechdrs, info->hdr->e_shnum)) { src[i] rather than src+1 is better as kallsyms(); > + strtab_size += strlen(&info->strtab[src[i].st_name])+1; > ndst++; > } > + } > > /* Append room for core symbols at end of core part. */ > info->symoffs = ALIGN(mod->core_size, symsect->sh_addralign ?: 1); > @@ -2312,15 +2317,15 @@ static void add_kallsyms(struct module * > mod->core_symtab = dst = mod->module_core + info->symoffs; > mod->core_strtab = s = mod->module_core + info->stroffs; > src = mod->symtab; > - *dst = *src; > *s++ = 0; This "*s++"line is also not needed since the content of src[0] is copied in the following loop. If my understanding is correct, the allsym table becomes as follows by applying this patch. ================== \0\0\0\0... # "\0" means null character in this case ================== It should be as follows. ==================== \0\0\0... ==================== This patch would work, but need extra one byte per module. Olease let us know if I misunderstand something. I didn't confirm with real machine. Thanks, Satoru > - for (ndst = i = 1; i < mod->num_symtab; ++i, ++src) { > - if (!is_core_symbol(src, info->sechdrs, info->hdr->e_shnum)) > - continue; > - > - dst[ndst] = *src; > - dst[ndst++].st_name = s - mod->core_strtab; > - s += strlcpy(s, &mod->strtab[src->st_name], KSYM_NAME_LEN) + 1; > + for (ndst = i = 0; i < mod->num_symtab; i++) { > + if (i == 0 || > + is_core_symbol(src+i, info->sechdrs, info->hdr->e_shnum)) { > + dst[ndst] = src[i]; > + dst[ndst++].st_name = s - mod->core_strtab; > + s += strlcpy(s, &mod->strtab[src[i].st_name], > + KSYM_NAME_LEN) + 1; > + } > } > mod->core_num_syms = ndst; > } > > > -- > To unsubscribe from this list: send the line "unsubscribe stable" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html -- 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/