block: take care not to overflow when calculating total iov length

commit 9f864c80913467312c7b8690e41fb5ebd1b50e92 upstream.

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/block/scsi_ioctl.c b/block/scsi_ioctl.c
index a8b5a10eb5b04cc15cdd8ddd26ed23fe7c55bc78..4f4230b79bb6ee3c8164e462e40d4bdea3dc1fcd 100644 (file)
--- a/block/scsi_ioctl.c
+++ b/block/scsi_ioctl.c
@@ -321,33 +321,47 @@ static int sg_io(struct request_queue *q, struct gendisk *bd_disk,
        if (hdr->iovec_count) {
                const int size = sizeof(struct sg_iovec) * hdr->iovec_count;
                size_t iov_data_len;
-               struct sg_iovec *iov;
+               struct sg_iovec *sg_iov;
+               struct iovec *iov;
+               int i;
 
-               iov = kmalloc(size, GFP_KERNEL);
-               if (!iov) {
+               sg_iov = kmalloc(size, GFP_KERNEL);
+               if (!sg_iov) {
                        ret = -ENOMEM;
                        goto out;
                }
 
-               if (copy_from_user(iov, hdr->dxferp, size)) {
-                       kfree(iov);
+               if (copy_from_user(sg_iov, hdr->dxferp, size)) {
+                       kfree(sg_iov);
                        ret = -EFAULT;
                        goto out;
                }
 
+               /*
+                * Sum up the vecs, making sure they don't overflow
+                */
+               iov = (struct iovec *) sg_iov;
+               iov_data_len = 0;
+               for (i = 0; i < hdr->iovec_count; i++) {
+                       if (iov_data_len + iov[i].iov_len < iov_data_len) {
+                               kfree(sg_iov);
+                               ret = -EINVAL;
+                               goto out;
+                       }
+                       iov_data_len += iov[i].iov_len;
+               }
+
                /* SG_IO howto says that the shorter of the two wins */
-               iov_data_len = iov_length((struct iovec *)iov,
-                                         hdr->iovec_count);
                if (hdr->dxfer_len < iov_data_len) {
-                       hdr->iovec_count = iov_shorten((struct iovec *)iov,
+                       hdr->iovec_count = iov_shorten(iov,
                                                       hdr->iovec_count,
                                                       hdr->dxfer_len);
                        iov_data_len = hdr->dxfer_len;
                }
 
-               ret = blk_rq_map_user_iov(q, rq, NULL, iov, hdr->iovec_count,
+               ret = blk_rq_map_user_iov(q, rq, NULL, sg_iov, hdr->iovec_count,
                                          iov_data_len, GFP_KERNEL);
-               kfree(iov);
+               kfree(sg_iov);
        } else if (hdr->dxfer_len)
                ret = blk_rq_map_user(q, rq, NULL, hdr->dxferp, hdr->dxfer_len,
                                      GFP_KERNEL);