Commit 5d1854e1 authored Dec 06, 2006 by Eric Sandeen Committed by Linus Torvalds Dec 07, 2006

[PATCH] reject corrupt swapfiles earlier



The fsfuzzer found this; with a corrupt small swapfile that claims to have
many pages:

  [root]# file swap.741.img
  swap.741.img: Linux/i386 swap file (new style) 1 (4K pages) size 1040191487 pages
  [root]# ls -l swap.741.img
  -rw-r--r-- 1 root root 16777216 Nov 22 05:18 swap.741.img

sys_swapon() will try to vmalloc all those pages, and -then- check to see if
the file is actually that large:

                if (!(p->swap_map = vmalloc(maxpages * sizeof(short)))) {
  <snip>
        if (swapfilesize && maxpages > swapfilesize) {
                printk(KERN_WARNING
                       "Swap area shorter than signature indicates\n");

It seems to me that it would make more sense to move this test up before
the vmalloc, with the other checks, to avoid the OOM-killer in this
situation...

Signed-off-by: Eric Sandeen <sandeen@redhat.com>
Cc: Hugh Dickins <hugh@veritas.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

parent 4af2bfc1

mm/swapfile.c

+5 −6

Original line number	Diff line number	Diff line
		@@ -1552,6 +1552,11 @@ asmlinkage long sys_swapon(const char __user * specialfile, int swap_flags)
		error = -EINVAL;
		if (!maxpages)
		goto bad_swap;
		if (swapfilesize && maxpages > swapfilesize) {
		printk(KERN_WARNING
		"Swap area shorter than signature indicates\n");
		goto bad_swap;
		}
		if (swap_header->info.nr_badpages && S_ISREG(inode->i_mode))
		goto bad_swap;
		if (swap_header->info.nr_badpages > MAX_SWAP_BADPAGES)
		@@ -1579,12 +1584,6 @@ asmlinkage long sys_swapon(const char __user * specialfile, int swap_flags)
		goto bad_swap;
		}

		if (swapfilesize && maxpages > swapfilesize) {
		printk(KERN_WARNING
		"Swap area shorter than signature indicates\n");
		error = -EINVAL;
		goto bad_swap;
		}
		if (nr_good_pages) {
		p->swap_map[0] = SWAP_MAP_BAD;
		p->max = maxpages;

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