Commit 6391af6f authored Jun 10, 2017 by David Windsor Committed by Kees Cook Jan 15, 2018

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 <dave@nullcore.net>
[kees: adjust commit log]
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: linux-fsdevel@vger.kernel.org
Signed-off-by: Kees Cook <keescook@chromium.org>

parent 6a9b8820

fs/fhandle.c

+1 −2

Original line number	Diff line number	Diff line
		@@ -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;

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