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Re: ssp, __strcpy_ck: just to be sure



tlaronde%polynum.com@localhost writes:

> On Tue, Nov 17, 2020 at 10:16:47AM -0500, Greg Troxel wrote:
>> 
>> tlaronde%polynum.com@localhost writes:
>> 
>> > But then I realized that I have not changed the offending line: the
>> > strcpy() call since there was no overflow problem: it was doing inplace
>> > rewrite, suppressing a prefix (doing basename(1) essentially).
>> 
>> Not sure what "inplace" means, but it sounds like it runs afoul of:
>
> simply something like : strcpy(buf, buf + shift);

That is undefined behavior, and thus wrong and needs to be fixed,
fortify or no.

>> and thus it is fair to alert on it.
>
> Yes, but the question was that it alerts only with arrays---but this is
> perhaps simply because it would be too costly to call strlen(3) or
> equivalent at runtime, and so, when the size is not known at compilation
> time, the alert doesn't work.

Perfectly ok to have a discussion  about how the tool can be improved,
but the code is UB and thus an alert is fair, being a member of the set
of all behaviors.

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