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

Reported-by: Dan Rosenberg <drosenberg@vsecurity.com>
Cc: stable@kernel.org
Signed-off-by: Jens Axboe <jaxboe@fusionio.com>

1 files changed, 24 insertions, 10 deletions

diff --git a/block/scsi_ioctl.c b/block/scsi_ioctl.c
index a8b5a10eb5b0..4f4230b79bb6 100644
--- 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);