On Wed, 24 Sep 2014 22:51:14 +0200 Rickard Strandqvist <rickard_strandqv...@spectrumdigital.se> wrote:
> 2014-09-24 17:41 GMT+02:00 Dan Carpenter <dan.carpen...@oracle.com>: > > On Wed, Sep 24, 2014 at 07:35:55AM -0700, Andi Kleen wrote: > >> On Wed, Sep 24, 2014 at 10:52:06AM +0300, Dan Carpenter wrote: > >> > On Tue, Sep 23, 2014 at 06:17:53PM -0700, Andi Kleen wrote: > >> > > On Wed, Sep 24, 2014 at 12:13:36AM +0200, Rickard Strandqvist wrote: > >> > > > Added a function strzcpy which works the same as strncpy, > >> > > > but guaranteed to produce the trailing null character. > >> > > > >> > > Do we really need the bizarre strncpy padding semantics for anything? > >> > > Why not just use strlcpy? > >> > > >> > We do need the padding in many places to prevent information leaks. > >> > >> Like where? > >> > > > > You're asking what would break if we switched every strncpy() to > > strlcpy() but it's not an easy question to answer. > > > > I've looked a lot at information leaks, but strings are still a blind > > spot for my Smatch. My check only looks at normal variables, arrays. > > Eventually I hope to fix this, of course. > > > > I did a git search and Rickard has added some examples, but there were > > definitely other places that rely strncpy() padding before. > > > > regards, > > dan carpenter > > > Hi > > If you want to see examples of this type of error, you can check the > patches I've done over the past two months. > So in linux-next > > git log --patch-with-stat > > And search for my email address. > > And there is also an approximately 20 more patches I waited to see if > I will be able to use a potential strzcpy :-) I have to say, this email thread has been a good demonstration of the effects of incomplete changelogging :( How's about you try again and this time include a *full* explanation of why you believe the kernel needs strzcpy()? Describe the problem, provide those examples, explain the proposed solution, etc. Also... I misread the code - that implementation indeed zeroes out to the end of the destination. I'm not sure that it does it very efficiently though - it repeatedly dereferences `src' just to obtain a null byte? A second nulling loop would be clearer and perhaps faster. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
