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Date: Sat, 31 Jan 2015 11:18:37 +0700 From: Arseny Solokha <asolokha@...kras.ru> To: Scott Wood <scottwood@...escale.com> CC: Benjamin Herrenschmidt <benh@...nel.crashing.org>, Paul Mackerras <paulus@...ba.org>, Michael Ellerman <mpe@...erman.id.au>, linuxppc-dev@...ts.ozlabs.org, linux-kernel@...r.kernel.org Subject: Re: [PATCH] powerpc/mm: bail out early when flushing TLB page > On Fri, 2015-01-30 at 19:08 +0700, Arseny Solokha wrote: >> MMU_NO_CONTEXT is conditionally defined as 0 or (unsigned int)-1. > > For nohash it is specifically -1. >> However, in __flush_tlb_page() a corresponding variable is only tested >> for open coded 0, which can cause NULL pointer dereference if `mm' >> argument was legitimately passed as such. >> >> Bail out early in case the first argument is NULL, thus eliminate confusion >> between different values of MMU_NO_CONTEXT and avoid disabling and then >> re-enabling preemption unnecessarily. > > How did you notice this? Did you see an oops, or was it code > inspection? I'm wondering what codepath gets here with mm == NULL. Just a code inspection. It didn't seemed right at the first glance. Arsény > > -Scott -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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