Messages in this thread | | | Date | Thu, 12 Jan 2012 13:19:54 -0800 (PST) | From | David Rientjes <> | Subject | Re: [PATCH] mm: Don't warn if memdup_user fails |
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On Thu, 12 Jan 2012, Pekka Enberg wrote:
> I think you missed Andrew's point. We absolutely want to issue a > kernel warning here because ecryptfs is misusing the memdup_user() > API. We must not let userspace processes allocate large amounts of > memory arbitrarily. >
I think it's good to fix ecryptfs like Tyler is doing and, at the same time, ensure that the len passed to memdup_user() makes sense prior to kmallocing memory with GFP_KERNEL. Perhaps something like
if (WARN_ON(len > PAGE_SIZE << PAGE_ALLOC_COSTLY_ORDER)) return ERR_PTR(-ENOMEM);
in which case __GFP_NOWARN is irrelevant. I think memdup_user() should definitely be taking gfp flags, though, so the caller can specify things like __GFP_NORETRY on its own to avoid infinitely looping in the page allocator trying reclaim and possibly calling the oom killer.
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