This is a note to let you know that I've just added the patch titled
exec: make argv/envp memory visible to oom-killer
to the 2.6.33-longterm tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/longterm/longterm-queue-2.6.33.git;a=summary
The filename of the patch is:
exec-make-argv-envp-memory-visible-to-oom-killer.patch
and it can be found in the queue-2.6.33 subdirectory.
If you, or anyone else, feels it should not be added to the 2.6.33 longterm
tree,
please let <[email protected]> know about it.
>From 3c77f845722158206a7209c45ccddc264d19319c Mon Sep 17 00:00:00 2001
From: Oleg Nesterov <[email protected]>
Date: Tue, 30 Nov 2010 20:55:34 +0100
Subject: exec: make argv/envp memory visible to oom-killer
From: Oleg Nesterov <[email protected]>
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 <[email protected]>
Reviewed-and-discussed-by: KOSAKI Motohiro <[email protected]>
Signed-off-by: Oleg Nesterov <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>
Cc: Moritz Muehlenhoff <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>
---
fs/exec.c | 28 ++++++++++++++++++++++++++--
include/linux/binfmts.h | 1 +
2 files changed, 27 insertions(+), 2 deletions(-)
--- a/fs/exec.c
+++ b/fs/exec.c
@@ -158,6 +158,21 @@ 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)
{
@@ -180,6 +195,8 @@ 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
@@ -273,6 +290,10 @@ 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)
{
@@ -991,6 +1012,7 @@ 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;
@@ -1415,8 +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) {
--- 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];
Patches currently in longterm-queue-2.6.33 which might be from [email protected]
are
/home/gregkh/linux/longterm/longterm-queue-2.6.33/queue-2.6.33/exec-make-argv-envp-memory-visible-to-oom-killer.patch
/home/gregkh/linux/longterm/longterm-queue-2.6.33/queue-2.6.33/relax-si_code-check-in-rt_sigqueueinfo-and-rt_tgsigqueueinfo.patch
/home/gregkh/linux/longterm/longterm-queue-2.6.33/queue-2.6.33/exec-copy-and-paste-the-fixes-into-compat_do_execve-paths.patch
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