autofs4 copy_dev_ioctl(): keep the value of ->size we'd used for allocation

X-Coverup: just ask spender
Cc: stable@vger.kernel.org
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

1 files changed, 6 insertions, 2 deletions

diff --git a/fs/autofs4/dev-ioctl.c b/fs/autofs4/dev-ioctl.c
index aaf96cb25452..ac7d921ed984 100644
--- a/fs/autofs4/dev-ioctl.c
+++ b/fs/autofs4/dev-ioctl.c
@@ -95,7 +95,7 @@ static int check_dev_ioctl_version(int cmd, struct autofs_dev_ioctl *param)
  */
 static struct autofs_dev_ioctl *copy_dev_ioctl(struct autofs_dev_ioctl __user *in)
 {
-        struct autofs_dev_ioctl tmp;
+        struct autofs_dev_ioctl tmp, *res;
 
         if (copy_from_user(&tmp, in, sizeof(tmp)))
                 return ERR_PTR(-EFAULT);
@@ -106,7 +106,11 @@ static struct autofs_dev_ioctl *copy_dev_ioctl(struct autofs_dev_ioctl __user *i
         if (tmp.size > (PATH_MAX + sizeof(tmp)))
                 return ERR_PTR(-ENAMETOOLONG);
 
-        return memdup_user(in, tmp.size);
+        res = memdup_user(in, tmp.size);
+        if (!IS_ERR(res))
+                res->size = tmp.size;
+
+        return res;
 }
 
 static inline void free_dev_ioctl(struct autofs_dev_ioctl *param)