bio: take care not overflow page count when mapping/copying user data

commit cb4644cac4a2797afc847e6c92736664d4b0ea34 upstream.

If the iovec is being set up in a way that causes uaddr + PAGE_SIZE
to overflow, we could end up attempting to map a huge number of
pages. Check for this invalid input type.

Reported-by: Dan Rosenberg <drosenberg@vsecurity.com>
Signed-off-by: Jens Axboe <jaxboe@fusionio.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

diff --git a/fs/bio.c b/fs/bio.c
index 3cba7ae..4ad38a6 100644 (file)
--- a/fs/bio.c
+++ b/fs/bio.c
@@ -593,6 +593,12 @@ struct bio *bio_copy_user_iov(struct request_queue *q, struct sg_iovec *iov,
                end = (uaddr + iov[i].iov_len + PAGE_SIZE - 1) >> PAGE_SHIFT;
                start = uaddr >> PAGE_SHIFT;
 
+               /*
+                * Overflow, abort
+                */
+               if (end < start)
+                       return ERR_PTR(-EINVAL);
+
                nr_pages += end - start;
                len += iov[i].iov_len;
        }
@@ -691,6 +697,12 @@ static struct bio *__bio_map_user_iov(struct request_queue *q,
                unsigned long end = (uaddr + len + PAGE_SIZE - 1) >> PAGE_SHIFT;
                unsigned long start = uaddr >> PAGE_SHIFT;
 
+               /*
+                * Overflow, abort
+                */
+               if (end < start)
+                       return ERR_PTR(-EINVAL);
+
                nr_pages += end - start;
                /*
                 * buffer must be aligned to at least hardsector size for now
@@ -718,7 +730,7 @@ static struct bio *__bio_map_user_iov(struct request_queue *q,
                unsigned long start = uaddr >> PAGE_SHIFT;
                const int local_nr_pages = end - start;
                const int page_limit = cur_page + local_nr_pages;
-               
+
                ret = get_user_pages_fast(uaddr, local_nr_pages,
                                write_to_vm, &pages[cur_page]);
                if (ret < local_nr_pages) {