From: Sasha Levin Subject: vfs: read file_handle only once in handle_to_path Date: Wed, 28 Jan 2015 15:30:43 -0500 Origin: http://article.gmane.org/gmane.linux.file-systems/92438 We used to read file_handle twice. Once to get the amount of extra bytes, and once to fetch the entire structure. This may be problematic since we do size verifications only after the first read, so if the number of extra bytes changes in userspace between the first and second calls, we'll have an incoherent view of file_handle. Instead, read the constant size once, and copy that over to the final structure without having to re-read it again. Signed-off-by: Sasha Levin --- Change in v2: - Use the f_handle pointer rather than size of struct fs/fhandle.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-) --- a/fs/fhandle.c +++ b/fs/fhandle.c @@ -195,8 +195,9 @@ static int handle_to_path(int mountdirfd goto out_err; } /* copy the full handle */ - if (copy_from_user(handle, ufh, - sizeof(struct file_handle) + + *handle = f_handle; + if (copy_from_user(&handle->f_handle, + &ufh->f_handle, f_handle.handle_bytes)) { retval = -EFAULT; goto out_handle;