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[04/23] vfs: copy struct mount.mnt_id to userspace using put_user()

Message ID 1497915397-93805-5-git-send-email-keescook@chromium.org (mailing list archive)
State New, archived
Headers show

Commit Message

Kees Cook June 19, 2017, 11:36 p.m. UTC
From: David Windsor <dave@nullcore.net>

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]
Signed-off-by: Kees Cook <keescook@chromium.org>
 fs/fhandle.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)
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diff --git a/fs/fhandle.c b/fs/fhandle.c
index 58a61f55e0d0..46e00ccca8f0 100644
--- a/fs/fhandle.c
+++ b/fs/fhandle.c
@@ -68,8 +68,7 @@  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;