From 6391af6f5829e8767c6d5e777194c9ecdd5d7ead Mon Sep 17 00:00:00 2001 From: David Windsor Date: Sat, 10 Jun 2017 22:50:31 -0400 Subject: [PATCH] vfs: Copy struct mount.mnt_id to userspace using put_user() The mnt_id field can be copied with put_user(), so there is no need to use copy_to_user(). In both cases, hardened usercopy is being bypassed since the size is constant, and not open to runtime manipulation. This patch is verbatim from Brad Spengler/PaX Team's PAX_USERCOPY whitelisting code in the last public patch of grsecurity/PaX based on my understanding of the code. Changes or omissions from the original code are mine and don't reflect the original grsecurity/PaX code. Signed-off-by: David Windsor [kees: adjust commit log] Cc: Alexander Viro Cc: linux-fsdevel@vger.kernel.org Signed-off-by: Kees Cook --- fs/fhandle.c | 3 +-- 1 file changed, 1 insertion(+), 2 deletions(-) diff --git a/fs/fhandle.c b/fs/fhandle.c index 0ace128f5d23..0ee727485615 100644 --- a/fs/fhandle.c +++ b/fs/fhandle.c @@ -69,8 +69,7 @@ static long do_sys_name_to_handle(struct path *path, } else retval = 0; /* copy the mount id */ - if (copy_to_user(mnt_id, &real_mount(path->mnt)->mnt_id, - sizeof(*mnt_id)) || + if (put_user(real_mount(path->mnt)->mnt_id, mnt_id) || copy_to_user(ufh, handle, sizeof(struct file_handle) + handle_bytes)) retval = -EFAULT; -- 2.11.0