From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S964956Ab1DNSPd (ORCPT ); Thu, 14 Apr 2011 14:15:33 -0400 Received: from mail.windriver.com ([147.11.1.11]:41893 "EHLO mail.windriver.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S964858Ab1DNR6M (ORCPT ); Thu, 14 Apr 2011 13:58:12 -0400 From: Paul Gortmaker To: stable@kernel.org, linux-kernel@vger.kernel.org Cc: stable-review@kernel.org, Oleg Nesterov , Linus Torvalds , Paul Gortmaker Subject: [34-longterm 136/209] exec: make argv/envp memory visible to oom-killer Date: Thu, 14 Apr 2011 13:54:54 -0400 Message-Id: <1302803767-9715-23-git-send-email-paul.gortmaker@windriver.com> X-Mailer: git-send-email 1.7.4.4 In-Reply-To: <1302803767-9715-1-git-send-email-paul.gortmaker@windriver.com> References: <1302803039-9400-1-git-send-email-paul.gortmaker@windriver.com> <1302803767-9715-1-git-send-email-paul.gortmaker@windriver.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Oleg Nesterov ===================================================================== | This is a commit scheduled for the next v2.6.34 longterm release. | | If you see a problem with using this for longterm, please comment.| ===================================================================== commit 3c77f845722158206a7209c45ccddc264d19319c upstream Brad Spengler published a local memory-allocation DoS that evades the OOM-killer (though not the virtual memory RLIMIT): http://www.grsecurity.net/~spender/64bit_dos.c execve()->copy_strings() can allocate a lot of memory, but this is not visible to oom-killer, nobody can see the nascent bprm->mm and take it into account. With this patch get_arg_page() increments current's MM_ANONPAGES counter every time we allocate the new page for argv/envp. When do_execve() succeds or fails, we change this counter back. Technically this is not 100% correct, we can't know if the new page is swapped out and turn MM_ANONPAGES into MM_SWAPENTS, but I don't think this really matters and everything becomes correct once exec changes ->mm or fails. Reported-by: Brad Spengler Reviewed-and-discussed-by: KOSAKI Motohiro Signed-off-by: Oleg Nesterov Signed-off-by: Linus Torvalds Signed-off-by: Paul Gortmaker --- fs/exec.c | 32 ++++++++++++++++++++++++++++++-- include/linux/binfmts.h | 1 + 2 files changed, 31 insertions(+), 2 deletions(-) diff --git a/fs/exec.c b/fs/exec.c index afd9977..8d4912f 100644 --- a/fs/exec.c +++ b/fs/exec.c @@ -158,6 +158,25 @@ out: #ifdef CONFIG_MMU +static void acct_arg_size(struct linux_binprm *bprm, unsigned long pages) +{ + struct mm_struct *mm = current->mm; + long diff = (long)(pages - bprm->vma_pages); + + if (!mm || !diff) + return; + + bprm->vma_pages = pages; + +#ifdef SPLIT_RSS_COUNTING + add_mm_counter(mm, MM_ANONPAGES, diff); +#else + spin_lock(&mm->page_table_lock); + add_mm_counter(mm, MM_ANONPAGES, diff); + spin_unlock(&mm->page_table_lock); +#endif +} + static struct page *get_arg_page(struct linux_binprm *bprm, unsigned long pos, int write) { @@ -180,6 +199,8 @@ static struct page *get_arg_page(struct linux_binprm *bprm, unsigned long pos, unsigned long size = bprm->vma->vm_end - bprm->vma->vm_start; struct rlimit *rlim; + acct_arg_size(bprm, size / PAGE_SIZE); + /* * We've historically supported up to 32 pages (ARG_MAX) * of argument strings even with small stacks @@ -269,6 +290,10 @@ static bool valid_arg_len(struct linux_binprm *bprm, long len) #else +static inline void acct_arg_size(struct linux_binprm *bprm, unsigned long pages) +{ +} + static struct page *get_arg_page(struct linux_binprm *bprm, unsigned long pos, int write) { @@ -987,6 +1012,7 @@ int flush_old_exec(struct linux_binprm * bprm) /* * Release all of the old mmap stuff */ + acct_arg_size(bprm, 0); retval = exec_mmap(bprm->mm); if (retval) goto out; @@ -1411,8 +1437,10 @@ int do_execve(char * filename, return retval; out: - if (bprm->mm) - mmput (bprm->mm); + if (bprm->mm) { + acct_arg_size(bprm, 0); + mmput(bprm->mm); + } out_file: if (bprm->file) { diff --git a/include/linux/binfmts.h b/include/linux/binfmts.h index c809e28..39798c6 100644 --- a/include/linux/binfmts.h +++ b/include/linux/binfmts.h @@ -29,6 +29,7 @@ struct linux_binprm{ char buf[BINPRM_BUF_SIZE]; #ifdef CONFIG_MMU struct vm_area_struct *vma; + unsigned long vma_pages; #else # define MAX_ARG_PAGES 32 struct page *page[MAX_ARG_PAGES]; -- 1.7.4.4