Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1750876AbVLLMj7 (ORCPT ); Mon, 12 Dec 2005 07:39:59 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751140AbVLLMj7 (ORCPT ); Mon, 12 Dec 2005 07:39:59 -0500 Received: from zproxy.gmail.com ([64.233.162.202]:49913 "EHLO zproxy.gmail.com") by vger.kernel.org with ESMTP id S1750876AbVLLMj6 (ORCPT ); Mon, 12 Dec 2005 07:39:58 -0500 DomainKey-Signature: a=rsa-sha1; q=dns; c=nofws; s=beta; d=gmail.com; h=received:message-id:date:from:to:subject:mime-version:content-type; b=IZWpLjn5mTtOSg4r8AOmhdvtFS+vdKspqIeWtlNVwiIiG+QWcXUiLwPiROWUUWWrPxaQV2pGmxcvR5ecv7S0jetyWn69w17rnBiKxLWGORW6Jk8a7XpA77PDthvcJxU7PK80x9vQj98uAxPIrhJmJDMXcWLEcgDu/D39NQljq4I= Message-ID: <81083a450512120439h69ccf938m12301985458ea69f@mail.gmail.com> Date: Mon, 12 Dec 2005 18:09:57 +0530 From: Ashutosh Naik To: anandhkrishnan@yahoo.com, linux-kernel@vger.kernel.org, rusty@rustcorp.com.au, rth@redhat.com, akpm@osdl.org, Greg KH Subject: [RFC][PATCH] Prevent overriding of Symbols in the Kernel, avoiding Undefined behaviour MIME-Version: 1.0 Content-Type: multipart/mixed; boundary="----=_Part_6792_6055943.1134391197809" Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 5038 Lines: 140 ------=_Part_6792_6055943.1134391197809 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable Content-Disposition: inline This patch is the next logical step after the following two threads http://www.uwsg.iu.edu/hypermail/linux/kernel/0511.2/2505.html http://www.ussg.iu.edu/hypermail/linux/kernel/0511.3/0036.html When a symbol is exported from the kernel, and say, a module would export the same symbol, there currently exists no mechanism to prevent the module from exporting this symbol. The module would still go ahead and export the symbol, the symbol table would now contain two copies of the exported symbol, and hell would break loose. This patch prevents that from happening, by checking the symbol table before relocation for all occurences of the Exported Symbol. If the symbol already exists, we branch out with -ENOEXEC. Currently, this search is sequential. Signed-off-by: Ashutosh Naik Signed-off-by: Anand Krishnan ------=_Part_6792_6055943.1134391197809 Content-Type: text/plain; name=mod-patch.txt; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: attachment; filename="mod-patch.txt" diff -Naurp linux-2.6.15-rc5-vanilla/kernel/module.c linux-2.6.15-rc5-mod/kernel/module.c --- linux-2.6.15-rc5-vanilla/kernel/module.c 2005-12-07 19:32:23.000000000 +0530 +++ linux-2.6.15-rc5-mod/kernel/module.c 2005-12-12 17:47:28.000000000 +0530 @@ -1204,6 +1204,63 @@ void *__symbol_get(const char *symbol) } EXPORT_SYMBOL_GPL(__symbol_get); +/* + * Ensure that an exported symbol [global namespace] does not already exist + * in the Kernel or in some other modules exported symbol table. + */ +static int verify_export_symbols(Elf_Shdr *sechdrs, + const char *strtab, + struct module *mod) +{ + struct kernel_symbol *exportsym, *gplsym; + unsigned long i,ret=0,value=0; + struct module *owner; + const unsigned long *crc; + unsigned long index=0; + + spin_lock_irq(&modlist_lock); + + exportsym = (struct kernel_symbol *)mod->syms; + gplsym = (struct kernel_symbol *)mod->gpl_syms; + + if (exportsym) + for (i = 0; i < mod->num_syms; exportsym++,i++) { + index = (unsigned long)(exportsym->name); + if (exportsym->name) { + value = __find_symbol(strtab + index, &owner, &crc,1); + + if (value != 0) + goto duplicate_sym; + } + } + + if (gplsym) + for (i = 0; i < mod->num_gpl_syms; gplsym++,i++) { + index = (unsigned long)(gplsym->name); + if (gplsym->name) { + value = __find_symbol(strtab + index, &owner, &crc,1); + + if (value != 0) + goto duplicate_gpl_sym; + } + } + + spin_unlock_irq(&modlist_lock); + /*Done*/ + return ret; + +duplicate_sym: + spin_unlock_irq(&modlist_lock); + printk("%s: Duplicate Exported Symbol found in %s\n", + strtab + index, mod->name); + return -ENOEXEC; +duplicate_gpl_sym: + spin_unlock_irq(&modlist_lock); + printk("%s: Duplicate Exported Symbol found in %s\n", + strtab + index, mod->name); + return -ENOEXEC; +} + /* Change all symbols so that sh_value encodes the pointer directly. */ static int simplify_symbols(Elf_Shdr *sechdrs, unsigned int symindex, @@ -1502,10 +1559,10 @@ static struct module *load_module(void _ { Elf_Ehdr *hdr; Elf_Shdr *sechdrs; - char *secstrings, *args, *modmagic, *strtab = NULL; + char *secstrings, *args, *modmagic, *strtab = NULL, *exportstrtab = NULL; unsigned int i, symindex = 0, strindex = 0, setupindex, exindex, - exportindex, modindex, obsparmindex, infoindex, gplindex, - crcindex, gplcrcindex, versindex, pcpuindex; + exportindex, exportstringindex, modindex, obsparmindex, infoindex, + gplindex, crcindex, gplcrcindex, versindex, pcpuindex; long arglen; struct module *mod; long err = 0; @@ -1585,6 +1642,7 @@ static struct module *load_module(void _ /* Optional sections */ exportindex = find_sec(hdr, sechdrs, secstrings, "__ksymtab"); + exportstringindex = find_sec(hdr,sechdrs, secstrings, "__ksymtab_strings"); gplindex = find_sec(hdr, sechdrs, secstrings, "__ksymtab_gpl"); crcindex = find_sec(hdr, sechdrs, secstrings, "__kcrctab"); gplcrcindex = find_sec(hdr, sechdrs, secstrings, "__kcrctab_gpl"); @@ -1736,6 +1794,13 @@ static struct module *load_module(void _ if (gplcrcindex) mod->gpl_crcs = (void *)sechdrs[gplcrcindex].sh_addr; + /* Find duplicate symbols */ + exportstrtab = (void *)sechdrs[exportstringindex].sh_addr; + err = verify_export_symbols(sechdrs, exportstrtab, mod); + + if (err < 0) + goto cleanup; + #ifdef CONFIG_MODVERSIONS if ((mod->num_syms && !crcindex) || (mod->num_gpl_syms && !gplcrcindex)) { ------=_Part_6792_6055943.1134391197809-- - 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/