From patchwork Mon Jul 18 03:31:50 2016 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Nicolas Pitre X-Patchwork-Id: 9234019 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork.web.codeaurora.org (Postfix) with ESMTP id 937DE6075D for ; Mon, 18 Jul 2016 03:47:31 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 87644212F2 for ; Mon, 18 Jul 2016 03:47:31 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id 7C1D526A99; Mon, 18 Jul 2016 03:47:31 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-6.9 required=2.0 tests=BAYES_00,RCVD_IN_DNSWL_HI autolearn=ham version=3.3.1 Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id E1C81212F2 for ; Mon, 18 Jul 2016 03:47:29 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751424AbcGRDrN (ORCPT ); Sun, 17 Jul 2016 23:47:13 -0400 Received: from alt32.smtp-out.videotron.ca ([24.53.0.21]:20185 "EHLO alt32.smtp-out.videotron.ca" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751326AbcGRDrM (ORCPT ); Sun, 17 Jul 2016 23:47:12 -0400 X-Greylist: delayed 900 seconds by postgrey-1.27 at vger.kernel.org; Sun, 17 Jul 2016 23:47:11 EDT Received: from yoda.home ([96.23.157.65]) by Videotron with SMTP id OzHsbJh5SYOXTOzHtb8QfF; Sun, 17 Jul 2016 23:32:10 -0400 X-Authority-Analysis: v=2.1 cv=Gfm35VjL c=1 sm=1 tr=0 a=keA3yYpnlypCNW5BNWqu+w==:117 a=keA3yYpnlypCNW5BNWqu+w==:17 a=L9H7d07YOLsA:10 a=9cW_t1CCXrUA:10 a=s5jvgZ67dGcA:10 a=cAmyUtKerLwA:10 a=KKAkSRfTAAAA:8 a=SjwPGEeTKsiiQuiMm4kA:9 a=cvBusfyB2V15izCimMoJ:22 Received: from xanadu.home (xanadu.home [192.168.2.2]) by yoda.home (Postfix) with ESMTP id 8201C2DA0639; Sun, 17 Jul 2016 23:32:08 -0400 (EDT) From: Nicolas Pitre To: linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org Cc: Alexander Viro , David Howells , Greg Ungerer Subject: [PATCH v2 04/10] binfmt_flat: clean up create_flat_tables() and stack accesses Date: Sun, 17 Jul 2016 23:31:50 -0400 Message-Id: <1468812716-30537-5-git-send-email-nicolas.pitre@linaro.org> X-Mailer: git-send-email 2.7.4 In-Reply-To: <1468812716-30537-1-git-send-email-nicolas.pitre@linaro.org> References: <1468812716-30537-1-git-send-email-nicolas.pitre@linaro.org> X-CMAE-Envelope: MS4wfMNqbfhan03FfSkJUF59efwzWGpIOtVnQ17cXK94v8cqwh8+6fDZr2Gxn2t8xylVW2Ul7Drog5ybUsTZ/PR0nTECVXcKgy8rFTWPJuftWvP0YESlP6lC LBp1tuL/OPTWibAptAqj7s7B6w01mi9gnGDW072p5SsPNd0uxrZ0VLaxkYkDLJt8AGqg+cKF72Z1nHLkTtq4SDKHstdhyNUPpxENUAynDggnUUkUaCph/yL0 0UgJtglylxeLbodxjp4kAQAKtu4/fRMjJP8uc0q07cX864xGgm3UlQNYspklkgz7IRA9hOZofRIvqr6B+md7Vw== Sender: linux-fsdevel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP In addition to better code clarity, this brings proper usage of user memory accessors everywhere the stack is touched. This is essential for making this work on MMU systems. Signed-off-by: Nicolas Pitre --- fs/binfmt_flat.c | 117 ++++++++++++++++++++++++++++++------------------------- 1 file changed, 63 insertions(+), 54 deletions(-) diff --git a/fs/binfmt_flat.c b/fs/binfmt_flat.c index 64feb873f0..9538901fe8 100644 --- a/fs/binfmt_flat.c +++ b/fs/binfmt_flat.c @@ -115,50 +115,58 @@ static int flat_core_dump(struct coredump_params *cprm) /* * create_flat_tables() parses the env- and arg-strings in new user * memory and creates the pointer tables from them, and puts their - * addresses on the "stack", returning the new stack pointer value. + * addresses on the "stack", recording the new stack pointer value. */ -static unsigned long create_flat_tables( - unsigned long pp, - struct linux_binprm * bprm) +static int create_flat_tables(struct linux_binprm * bprm, unsigned long arg_start) { - unsigned long *argv,*envp; - unsigned long * sp; - char * p = (char*)pp; - int argc = bprm->argc; - int envc = bprm->envc; - char uninitialized_var(dummy); - - sp = (unsigned long *)p; - sp -= (envc + argc + 2) + 1 + (flat_argvp_envp_on_stack() ? 2 : 0); - sp = (unsigned long *) ((unsigned long)sp & -FLAT_STACK_ALIGN); - argv = sp + 1 + (flat_argvp_envp_on_stack() ? 2 : 0); - envp = argv + (argc + 1); + char __user *p; + unsigned long __user *sp; + long i, len; + p = (char __user *)arg_start; + sp = (unsigned long __user *)current->mm->start_stack; + + sp -= bprm->envc + 1; + sp -= bprm->argc + 1; + sp -= flat_argvp_envp_on_stack() ? 2 : 0; + sp -= 1; /* &argc */ + + current->mm->start_stack = (unsigned long)sp & -FLAT_STACK_ALIGN; + sp = (unsigned long __user *)current->mm->start_stack; + + __put_user(bprm->argc, sp++); if (flat_argvp_envp_on_stack()) { - put_user((unsigned long) envp, sp + 2); - put_user((unsigned long) argv, sp + 1); - } - - put_user(argc, sp); - current->mm->arg_start = (unsigned long) p; - while (argc-->0) { - put_user((unsigned long) p, argv++); - do { - get_user(dummy, p); p++; - } while (dummy); - } - put_user((unsigned long) NULL, argv); - current->mm->arg_end = current->mm->env_start = (unsigned long) p; - while (envc-->0) { - put_user((unsigned long)p, envp); envp++; - do { - get_user(dummy, p); p++; - } while (dummy); - } - put_user((unsigned long) NULL, envp); - current->mm->env_end = (unsigned long) p; - return (unsigned long)sp; + unsigned long argv, envp; + argv = (unsigned long)(sp + 2); + envp = (unsigned long)(sp + 2 + bprm->argc + 1); + __put_user(argv, sp++); + __put_user(envp, sp++); + } + + current->mm->arg_start = (unsigned long)p; + for (i = bprm->argc; i > 0; i--) { + __put_user((unsigned long)p, sp++); + len = strnlen_user(p, MAX_ARG_STRLEN); + if (!len || len > MAX_ARG_STRLEN) + return -EINVAL; + p += len; + } + __put_user(0, sp++); + current->mm->arg_end = (unsigned long)p; + + current->mm->env_start = (unsigned long) p; + for (i = bprm->envc; i > 0; i--) { + __put_user((unsigned long)p, sp++); + len = strnlen_user(p, MAX_ARG_STRLEN); + if (!len || len > MAX_ARG_STRLEN) + return -EINVAL; + p += len; + } + __put_user(0, sp++); + current->mm->env_end = (unsigned long)p; + + return 0; } /****************************************************************************/ @@ -854,7 +862,7 @@ static int load_flat_binary(struct linux_binprm * bprm) { struct lib_info libinfo; struct pt_regs *regs = current_pt_regs(); - unsigned long sp, stack_len; + unsigned long stack_len; unsigned long start_addr; int res; int i, j; @@ -868,11 +876,10 @@ static int load_flat_binary(struct linux_binprm * bprm) * pedantic and include space for the argv/envp array as it may have * a lot of entries. */ -#define TOP_OF_ARGS (PAGE_SIZE * MAX_ARG_PAGES - sizeof(void *)) - stack_len = TOP_OF_ARGS - bprm->p; /* the strings */ - stack_len += (bprm->argc + 1) * sizeof(char *); /* the argv array */ - stack_len += (bprm->envc + 1) * sizeof(char *); /* the envp array */ - stack_len += FLAT_STACK_ALIGN - 1; /* reserve for upcoming alignment */ + stack_len = PAGE_SIZE * MAX_ARG_PAGES - bprm->p; /* the strings */ + stack_len += (bprm->argc + 1) * sizeof(char *); /* the argv array */ + stack_len += (bprm->envc + 1) * sizeof(char *); /* the envp array */ + stack_len = ALIGN(stack_len, FLAT_STACK_ALIGN); res = load_flat_file(bprm, &libinfo, 0, &stack_len); if (res < 0) @@ -890,16 +897,18 @@ static int load_flat_binary(struct linux_binprm * bprm) set_binfmt(&flat_format); - sp = ((current->mm->context.end_brk + stack_len + 3) & ~3) - 4; - DBG_FLT("sp=%lx\n", sp); + /* Stash our initial stack pointer into the mm structure */ + current->mm->start_stack = + ((current->mm->context.end_brk + stack_len + 3) & ~3) - 4; + DBG_FLT("sp=%lx\n", current->mm->start_stack); /* copy the arg pages onto the stack */ - res = transfer_args_to_stack(bprm, &sp); + res = transfer_args_to_stack(bprm, ¤t->mm->start_stack); + if (!res) + res = create_flat_tables(bprm, current->mm->start_stack); if (res) return res; - sp = create_flat_tables(sp, bprm); - /* Fake some return addresses to ensure the call chain will * initialise library in order for us. We are required to call * lib 1 first, then 2, ... and finally the main program (id 0). @@ -910,14 +919,14 @@ static int load_flat_binary(struct linux_binprm * bprm) for (i = MAX_SHARED_LIBS-1; i>0; i--) { if (libinfo.lib_list[i].loaded) { /* Push previos first to call address */ - --sp; put_user(start_addr, (unsigned long *)sp); + unsigned long __user *sp; + current->mm->start_stack -= sizeof(unsigned long); + sp = (unsigned long __user *)current->mm->start_stack; + __put_user(start_addr, sp); start_addr = libinfo.lib_list[i].entry; } } #endif - - /* Stash our initial stack pointer into the mm structure */ - current->mm->start_stack = sp; #ifdef FLAT_PLAT_INIT FLAT_PLAT_INIT(regs);