RE: [PATCH bpf v2 1/2] lib/strncpy_from_user.c: Don't overcopy bytes after NUL terminator

[David Laight]

From: Daniel Xu
> Sent: 05 November 2020 02:26
...
> --- a/lib/strncpy_from_user.c
> +++ b/lib/strncpy_from_user.c
> @@ -35,17 +35,22 @@ static inline long do_strncpy_from_user(char *dst, const char __user *src,
>  		goto byte_at_a_time;
> 
>  	while (max >= sizeof(unsigned long)) {
> -		unsigned long c, data;
> +		unsigned long c, data, mask, *out;
> 
>  		/* Fall back to byte-at-a-time if we get a page fault */
>  		unsafe_get_user(c, (unsigned long __user *)(src+res), byte_at_a_time);

It's not related to this change, but since both addresses
are aligned (checked earlier) a page fault on the word read
is fatal.

	David

-
Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK
Registration No: 1397386 (Wales)