On Tue, 2021-08-24 at 20:26 +0200, Borislav Petkov wrote:

On Tue, Aug 24, 2021 at 12:28:07PM +0200, Len Baker wrote:

quoted

This is a task of the KSPP [1] and the main reason is to clean up the
proliferation of str*cpy functions in the kernel.

That I understood - you prominently explain where the patches stem from.

What I can't parse is that formulation "previous step". What previous
step do you mean?

quoted

Yes, you are right. The same discussion happened in the v3 review [2] and
I agree with the reasons that Robert Richter exposed. Using the strlen()
implementation it is not necessary to check the return code of strcpy and
we can assume a silent truncation.

[2] https://lore.kernel.org/linux-hardening/YRN+8u59lJ6MWsOL@rric.localdomain/ (local)

Ok, looking at the asm, gcc is actually smart enough not to call
strlen() twice on the same buffer.

But then there's this in the strscpy() kernel-doc comment:

"The destination buffer is always NUL terminated, unless it's
zero-sized."

so looking at the code, we're merrily decrementing len but nothing's
checking whether len can become 0. Because if it does, strscpy() will
do:

	if (count == 0 || WARN_ON_ONCE(count > INT_MAX))
		return -E2BIG;

so if p ends up pointing to something which is *not* '\0', strlen() will
go off into the weeds.

So I don't care if it doesn't look just as nice - it better be correct
in all cases first.

It's all somehat unnecessary as it seems it's guaranteed not to overflow.

$ git grep -n -w OTHER_LABEL next-20210820
next-20210820:drivers/edac/edac_mc.c:1118:                              strcpy(p, OTHER_LABEL);
next-20210820:drivers/edac/edac_mc.c:1119:                              p += strlen(OTHER_LABEL);
next-20210820:include/linux/edac.h:57:#define OTHER_LABEL " or "
next-20210820:include/linux/edac.h:470: char label[(EDAC_MC_LABEL_LEN + 1 + sizeof(OTHER_LABEL)) * EDAC_MAX_LABELS];

Also the array size of char label is too large.

First by 1 * EDAC_MAX_LABELS as sizeof(OTHER_LABEL) is 5 not 4 and
second there can only be EDAC_MAX_LABELS - 1 uses of OTHER_LABEL.

And I would remove the define for OTHER_LABEL and use " or " directly.

Lastly, this could be easier to understand using stpcpy and/or scnprintf.