Messages in this thread | | | Subject | Re: [PATCH] powerpc/mm: bail out early when flushing TLB page | From | Scott Wood <> | Date | Fri, 30 Jan 2015 15:53:01 -0600 |
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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.
-Scott
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