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Mon, 13 Apr 2020 07:14:32 -0700 (PDT) Received: from xz-x1 ([2607:9880:19c0:32::2]) by smtp.gmail.com with ESMTPSA id w2sm2374972qtv.42.2020.04.13.07.14.30 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 13 Apr 2020 07:14:31 -0700 (PDT) Date: Mon, 13 Apr 2020 10:14:29 -0400 From: Peter Xu To: Naresh Kamboju Cc: open list , "open list:KERNEL SELFTEST FRAMEWORK" , linux-mm , lkft-triage@lists.linaro.org, Shuah Khan , Anders Roxell , Christophe Leroy , Andrew Morton , Leonardo Bras , Michael Ellerman , Mike Rapoport , Arnd Bergmann , Jules Irenge , "Huang, Ying" , Pankaj Gupta , Rik van Riel , Hugh Dickins , Minchan Kim , Mel Gorman , Dave Hansen , Mateusz Nosek , Sebastian Andrzej Siewior , Kees Cook , Vlastimil Babka , Hillf Danton Subject: Re: i386: selftests: vm: compaction_test: BUG: kernel NULL pointer dereference, address: 00000000 Message-ID: <20200413141429.GE38470@xz-x1> References: <20200412214150.GB38470@xz-x1> MIME-Version: 1.0 In-Reply-To: X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable Content-Disposition: inline X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Mon, Apr 13, 2020 at 04:51:25PM +0530, Naresh Kamboju wrote: > On Mon, 13 Apr 2020 at 03:12, Peter Xu wrote: > > And since this one is very easy to reproduce, I finally noticed that > > we have wrongly enabled uffd-wp on x86_32, which is definely not going > > to work... Because we'll use bit 2 of swap entry assuming that's the > > uffd-wp bit, while that's part of swp offset on 32bit systems. > > > > Naresh, could you try whether below change fixes the issue for you? > > > > diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig > > index 8d078642b4be..7ac524d1316e 100644 > > --- a/arch/x86/Kconfig > > +++ b/arch/x86/Kconfig > > @@ -149,7 +149,7 @@ config X86 > > select HAVE_ARCH_TRACEHOOK > > select HAVE_ARCH_TRANSPARENT_HUGEPAGE > > select HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD if X86_64 > > - select HAVE_ARCH_USERFAULTFD_WP if USERFAULTFD > > + select HAVE_ARCH_USERFAULTFD_WP if X86_64 && USERFAULTF= D > > select HAVE_ARCH_VMAP_STACK if X86_64 > > select HAVE_ARCH_WITHIN_STACK_FRAMES > > select HAVE_ASM_MODVERSIONS > > >=20 > Tested-by: Naresh Kamboju >=20 > The above patch tested and did not notice the crash. > + cd /opt/kselftests/default-in-kernel/vm/ > + ./compaction_test > No of huge pages allocated =3D 297 > + ./compaction_test > [ 46.059785] kauditd_printk_skb: 15 callbacks suppressed > [ 46.059786] audit: type=3D1334 audit(1586776582.927:25): prog-id=3D17 = op=3DUNLOAD > [ 46.071997] audit: type=3D1334 audit(1586776582.927:26): prog-id=3D16 = op=3DUNLOAD > No of huge pages allocated =3D 160 >=20 > Full test log, > https://lkft.validation.linaro.org/scheduler/job/1362495#L1308 >=20 > Build artifacts. > https://builds.tuxbuild.com/w0ol7cCsGan0wzPp7bNqkg/ Thanks! I'll post a formal patch soon. --=20 Peter Xu