From: Joe Perches

Sent: 09 August 2021 18:19

On Mon, 2021-08-09 at 12:05 +0200, Robert Richter wrote:

quoted

On 08.08.21 13:26:17, Len Baker wrote:

quoted

quoted

Perhaps this should use scnprintf rather than strscpy
Something like:
			n += scnprintf(buf + n, len - n, "%s",
				       p == e->label ? dim->label : OTHER_LABEL);

In the first version [1] the scnprintf was used but Robert Richter don't
see any benefit compared with the current implementation.

[1] https://lore.kernel.org/linux-hardening/20210725162954.9861-1-len.baker@gmx.com/ (local)

Reason is that there is the assumption that p must always point at the
end of the string and its trailing zero byte. I am not opposed using
the string function's return code instead of strlen() to get the
length. But why using formated output if strscpy() can be used?

strscpy and scnprintf have different return values and it's simpler
and much more common to use scnprintf for appended strings that are
limited to a specific buffer length.

scnprintf() will be a lot slower, but has a much better return value
than most of the strxxxcpy() functions.

The only slight problem is that you can't differentiate overflow
from a max-length output.

Trouble is fixing that adds 'yet another set of functions'.
Clearly we need the yellow with purple stripe ones :-)
Probably:
	offset = xxx(buf, len, offset, ......)
where offset == len on truncation.

	David

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