On Fri, Sep 12 2014, Andrew Morton <a...@linux-foundation.org> wrote:
> On Wed, 27 Aug 2014 09:36:01 +0200 Rasmus Villemoes > <li...@rasmusvillemoes.dk> wrote: > >> lib/string.c contains two functions, strnicmp and strncasecmp, which >> do roughly the same thing, namely compare two strings >> case-insensitively up to a given bound. They have slightly different >> implementations, but the only important difference is that strncasecmp >> doesn't handle len==0 appropriately; it effectively becomes strcasecmp >> in that case. strnicmp correctly says that two strings are always >> equal in their first 0 characters. >> >> strncasecmp is the POSIX name for this functionality. So rename the >> non-broken function to the standard name. To minimize the impact on >> the rest of the kernel (and since both are exported to modules), make >> strnicmp a wrapper for strncasecmp. > > I guess it's safe to assume that nobody was depending on the > strncasecmp() bug. Hm, I thought so as well, but decided to double check. I found one minor issue; maybe Tejun can tell if my analysis is correct. In drivers/ata/libata-core.c, ata_parse_force_one(), it is not immediately clear to me that val cannot end up being the empty string. With the buggy strncasecmp, the continue branch is always followed (since fp->name is not empty); however, with strncasecmp with the correct semantics, the empty string is obviously a prefix of every fp->name. So even though the comment says that "1.5" is an ok abbreviation of "1.5Gbps", I don't think the intention was to allow "" to be an abbreviation of everything. Anyway, the worst that can happen seems to be that "ambigious value" [sic] becomes the *reason instead of "unknown value". I may have overlooked similar issues; my checking was basically "is the length parameter an explicit non-zero number or strlen() of some static data in some table (where I assume empty strings do not lurk)". > Yes, please prepare the strnicmp()->strncasecmp() patches and let's get > them merged up. After a kernel release or two we can zap the > back-compat wrapper. Will do. Is there a fixed SHA1 I can refer to in the commit logs? > And it isn't just "out of tree modules" that we should be concerned > about - we'll commonly find that "to be in tree" code is using > interfaces which we're trying to alter or remove, so it takes a cycle > or two to get everything propagated. Most of this code can be found in > linux-next. Would it make sense to add a checkpatch warning to ensure new users are not introduced, and then remove it when the wrapper is also removed? Thanks, Rasmus -- 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/
