staging: lustre: libcfs: double copy bug

The problem is that we copy hdr.ioc_len, we verify it, then we copy it
again without checking to see if it has changed in between the two
copies.

This could result in an information leak.

Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 13 insertions, 2 deletions

diff --git a/drivers/staging/lustre/lnet/libcfs/linux/linux-module.c b/drivers/staging/lustre/lnet/libcfs/linux/linux-module.c
index 3f5d58babc2f..075826bd3a2a 100644
--- a/drivers/staging/lustre/lnet/libcfs/linux/linux-module.c
+++ b/drivers/staging/lustre/lnet/libcfs/linux/linux-module.c
@@ -122,7 +122,7 @@ int libcfs_ioctl_getdata(struct libcfs_ioctl_hdr **hdr_pp,
                          const struct libcfs_ioctl_hdr __user *uhdr)
 {
         struct libcfs_ioctl_hdr hdr;
-        int err = 0;
+        int err;
 
         if (copy_from_user(&hdr, uhdr, sizeof(hdr)))
                 return -EFAULT;
@@ -150,9 +150,20 @@ int libcfs_ioctl_getdata(struct libcfs_ioctl_hdr **hdr_pp,
                 return -ENOMEM;
 
         if (copy_from_user(*hdr_pp, uhdr, hdr.ioc_len)) {
-                LIBCFS_FREE(*hdr_pp, hdr.ioc_len);
                 err = -EFAULT;
+                goto free;
         }
+
+        if ((*hdr_pp)->ioc_version != hdr.ioc_version ||
+            (*hdr_pp)->ioc_len != hdr.ioc_len) {
+                err = -EINVAL;
+                goto free;
+        }
+
+        return 0;
+
+free:
+        LIBCFS_FREE(*hdr_pp, hdr.ioc_len);
         return err;
 }