Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932400Ab1DMP53 (ORCPT ); Wed, 13 Apr 2011 11:57:29 -0400 Received: from kroah.org ([198.145.64.141]:54648 "EHLO coco.kroah.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932348Ab1DMP4I (ORCPT ); Wed, 13 Apr 2011 11:56:08 -0400 X-Mailbox-Line: From gregkh@clark.kroah.org Wed Apr 13 08:51:50 2011 Message-Id: <20110413155150.755465795@clark.kroah.org> User-Agent: quilt/0.48-16.4 Date: Wed, 13 Apr 2011 08:51:36 -0700 From: Greg KH To: linux-kernel@vger.kernel.org, stable@kernel.org Cc: stable-review@kernel.org, torvalds@linux-foundation.org, akpm@linux-foundation.org, alan@lxorguk.ukuu.org.uk, Oleg Nesterov , Moritz Muehlenhoff Subject: [72/74] exec: make argv/envp memory visible to oom-killer In-Reply-To: <20110413155406.GA22568@kroah.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3417 Lines: 119 2.6.32-longterm review patch. If anyone has any objections, please let us know. ------------------ From: Oleg Nesterov 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 Cc: Moritz Muehlenhoff Signed-off-by: Greg Kroah-Hartman --- fs/exec.c | 28 ++++++++++++++++++++++++++-- include/linux/binfmts.h | 1 + 2 files changed, 27 insertions(+), 2 deletions(-) --- a/fs/exec.c +++ b/fs/exec.c @@ -159,6 +159,21 @@ 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; + + down_write(&mm->mmap_sem); + mm->total_vm += diff; + up_write(&mm->mmap_sem); +} + static struct page *get_arg_page(struct linux_binprm *bprm, unsigned long pos, int write) { @@ -181,6 +196,8 @@ static struct page *get_arg_page(struct 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 @@ -274,6 +291,10 @@ static bool valid_arg_len(struct linux_b #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) { @@ -981,6 +1002,7 @@ int flush_old_exec(struct linux_binprm * /* * Release all of the old mmap stuff */ + acct_arg_size(bprm, 0); retval = exec_mmap(bprm->mm); if (retval) goto out; @@ -1408,8 +1430,10 @@ 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) { --- 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]; -- 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/