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exec: make argv/envp memory visible to oom-killer
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> Cc: stable@kernel.org Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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parent
37a09f0745
commit
3c77f84572
32
fs/exec.c
32
fs/exec.c
@ -164,6 +164,25 @@ out:
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#ifdef CONFIG_MMU
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static void acct_arg_size(struct linux_binprm *bprm, unsigned long pages)
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{
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struct mm_struct *mm = current->mm;
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long diff = (long)(pages - bprm->vma_pages);
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if (!mm || !diff)
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return;
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bprm->vma_pages = pages;
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#ifdef SPLIT_RSS_COUNTING
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add_mm_counter(mm, MM_ANONPAGES, diff);
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#else
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spin_lock(&mm->page_table_lock);
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add_mm_counter(mm, MM_ANONPAGES, diff);
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spin_unlock(&mm->page_table_lock);
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#endif
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}
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static struct page *get_arg_page(struct linux_binprm *bprm, unsigned long pos,
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int write)
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{
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@ -186,6 +205,8 @@ static struct page *get_arg_page(struct linux_binprm *bprm, unsigned long pos,
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unsigned long size = bprm->vma->vm_end - bprm->vma->vm_start;
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struct rlimit *rlim;
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acct_arg_size(bprm, size / PAGE_SIZE);
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/*
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* We've historically supported up to 32 pages (ARG_MAX)
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* of argument strings even with small stacks
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@ -276,6 +297,10 @@ static bool valid_arg_len(struct linux_binprm *bprm, long len)
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#else
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static inline void acct_arg_size(struct linux_binprm *bprm, unsigned long pages)
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{
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}
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static struct page *get_arg_page(struct linux_binprm *bprm, unsigned long pos,
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int write)
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{
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@ -1003,6 +1028,7 @@ int flush_old_exec(struct linux_binprm * bprm)
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/*
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* Release all of the old mmap stuff
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*/
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acct_arg_size(bprm, 0);
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retval = exec_mmap(bprm->mm);
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if (retval)
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goto out;
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@ -1426,8 +1452,10 @@ int do_execve(const char * filename,
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return retval;
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out:
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if (bprm->mm)
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mmput (bprm->mm);
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if (bprm->mm) {
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acct_arg_size(bprm, 0);
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mmput(bprm->mm);
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}
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out_file:
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if (bprm->file) {
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@ -29,6 +29,7 @@ struct linux_binprm{
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char buf[BINPRM_BUF_SIZE];
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#ifdef CONFIG_MMU
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struct vm_area_struct *vma;
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unsigned long vma_pages;
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#else
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# define MAX_ARG_PAGES 32
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struct page *page[MAX_ARG_PAGES];
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