Date: Thu, 8 Feb 2018 20:47:57 -0500 From: Daniel Micay <danielmicay@...il.com> To: Matthew Wilcox <willy@...radead.org> Cc: Jann Horn <jannh@...gle.com>, linux-mm@...ck.org, Kernel Hardening <kernel-hardening@...ts.openwall.com>, kernel list <linux-kernel@...r.kernel.org>, "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>, Kees Cook <keescook@...omium.org> Subject: Re: [RFC] Warn the user when they could overflow mapcount I think there are likely legitimate programs mapping something a bunch of times. Falling back to a global object -> count mapping (an rbtree / radix trie or whatever) with a lock once it hits saturation wouldn't risk breaking something. It would permanently leave the inline count saturated and just use the address of the inline counter as the key for the map to find the 64-bit counter. Once it gets to 0 in the map, it can delete it from the map and do the standard freeing process, avoiding leaks. It would really just make it a 64-bit reference count heavily size optimized for the common case. It would work elsewhere too, not just this case.
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