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authorOleg Nesterov <oleg@redhat.com>2010-11-30 20:55:34 +0100
committerGreg Kroah-Hartman <gregkh@suse.de>2011-04-14 16:53:55 -0700
commitd3de146b4e4fcf817cee3831c0396ec8e8e2864e (patch)
tree531752a709427bb141e285e4af92696b33677e56 /fs
parent40521c939c106814166d9bc72f85e6aa5bfa868d (diff)
exec: make argv/envp memory visible to oom-killer
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 <spender@grsecurity.net> Reviewed-and-discussed-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com> Signed-off-by: Oleg Nesterov <oleg@redhat.com> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> Cc: Moritz Muehlenhoff <jmm@debian.org> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
Diffstat (limited to 'fs')
-rw-r--r--fs/exec.c28
1 files changed, 26 insertions, 2 deletions
diff --git a/fs/exec.c b/fs/exec.c
index 68083fab2c9f..07e5507594ed 100644
--- 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 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
@@ -274,6 +291,10 @@ 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)
{
@@ -981,6 +1002,7 @@ 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;
@@ -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) {