[PATCH] limit minixfs dir_pages on corrupted dir i_size, CVE-2006-6058

Eric Sandeen
2007-08-09T18:46:38Z

This attempts to address CVE-2006-6058
http://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2006-6058

first reported at http://projects.info-pull.com/mokb/MOKB-17-11-2006.html

Essentially a corrupted minix dir inode reporting a very large
i_size will loop for a very long time in minix_readdir, minix_find_entry,
etc, because on EIO they just move on to try the next page. This is
under the BKL, printk'ing as well. This can lock up the machine
for a very long time. A simple approach is to at least limit the nr. of
pages attempted to no more than s_max_size. (s_max_size is about 256MB for
V1, but 2GB for V2; this could still result in a lot of EIO reads in the V2
case, should the retry loops in minix_readdir & friends be short-circuited
somehow instead? A simple "break" rather than "continue" on error would
certainly resolve it, too...)

Signed-off-by: Eric Sandeen <sandeen@redhat.com>

--- linux-2.6.22-rc4.orig/fs/minix/dir.c
+++ linux-2.6.22-rc4/fs/minix/dir.c
@@ -42,7 +42,15 @@ minix_last_byte(struct inode *inode, uns

static inline unsigned long dir_pages(struct inode *inode)
{
- return (inode->i_size+PAGE_CACHE_SIZE-1)>>PAGE_CACHE_SHIFT;
+ loff_t size = inode->i_size;
+
+ if (size > minix_sb(inode->i_sb)->s_max_size) {
+ printk("%s: inode %lld i_size > s_max_size\n",
+ __FUNCTION__, inode->i_size);
+ size = minix_sb(inode->i_sb)->s_max_size;
+ }
+
+ return (size+PAGE_CACHE_SIZE-1)>>PAGE_CACHE_SHIFT;
}

static int dir_commit_chunk(struct page *page, unsigned from, unsigned to)