sg_start_req(): make sure that there's not too many elements in iovec

[ Upstream commit 451a2886b6bf90e2fb378f7c46c655450fb96e81 ]

unfortunately, allowing an arbitrary 16bit value means a possibility of
overflow in the calculation of total number of pages in bio_map_user_iov() -
we rely on there being no more than PAGE_SIZE members of sum in the
first loop there.  If that sum wraps around, we end up allocating
too small array of pointers to pages and it's easy to overflow it in
the second loop.

X-Coverup: TINC (and there's no lumber cartel either)
Cc: stable@vger.kernel.org # way, way back
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Sasha Levin <sasha.levin@oracle.com>

diff --git a/drivers/scsi/sg.c b/drivers/scsi/sg.c
index 07b2ea1fbf0dd51b828cc10cfefc78f4e99341ae..b3c8aabfd687b2eb34d03aaef64aa6d4b461b54d 100644 (file)
--- a/drivers/scsi/sg.c
+++ b/drivers/scsi/sg.c
@@ -1785,6 +1785,9 @@ sg_start_req(Sg_request *srp, unsigned char *cmd)
                        md->from_user = 0;
        }
 
+       if (unlikely(iov_count > UIO_MAXIOV))
+               return -EINVAL;
+
        if (iov_count) {
                int len, size = sizeof(struct sg_iovec) * iov_count;
                struct iovec *iov;