From mboxrd@z Thu Jan 1 00:00:00 1970 From: Nadav Amit Date: Fri, 26 Nov 2021 17:49:01 +0000 Subject: Re: [PATCH 4.9] hugetlbfs: flush TLBs correctly after huge_pmd_unshare Message-Id: List-Id: References: <3BD89231-2CB9-4CE5-B0FA-5B58419D7CB8@gmail.com> <7a2feed4-7c73-c7ad-881e-c980235c8293@cambridgegreys.com> In-Reply-To: <7a2feed4-7c73-c7ad-881e-c980235c8293@cambridgegreys.com> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: Anton Ivanov Cc: Nick Piggin , Peter Zijlstra , Will Deacon , "Aneesh Kumar K.V" , LKML , Linux-MM , linux-s390 , linux-ia64@vger.kernel.org, linux-sh@vger.kernel.org, linux-um@lists.infradead.org, linux-arm-kernel@lists.infradead.org, linux-arch , Mike Kravetz > On Nov 26, 2021, at 2:21 AM, Anton Ivanov wrote: > > > > On 26/11/2021 06:08, Nadav Amit wrote: >> Below is a patch to address CVE-2021-4002 [1] that I created to backport >> to 4.9. The stable kernels of 4.14 and prior ones do not have unified >> TLB flushing code, and I managed to mess up the arch code a couple of >> times. >> Now that the CVE is public, I would appreciate your review of this >> patch. I send 4.9 for review - the other ones (4.14 and prior) are >> pretty similar. >> [1] https://www.openwall.com/lists/oss-security/2021/11/25/1 >> Thanks, >> Nadav > > I do not quite see the rationale for patching um > > It supports only standard size pages. You should not be able to map a huge page there (and hugetlbfs). > > I have "non-standard page size" somewhere towards the end of my queue, but it keeps falling through - not enough spare time to work on it. Thanks for your review. I did not look at the dependencies, so I did not even look if hugetlbfs depends on !um. Do you prefer that for um, I will just do a BUG()? I prefer to have a stub just to avoid potential build issues.