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b=zSBbGZ8wsMBZ/5fbDWSTqmBjWK679FRGmfXXqPj09EDIrYSieZBhDOZPWFQ8YZtg8t rjOYhnDVDszCfz6X8LPGSkpURkl46volUHuqwWx98Cez4Gk8mFp1gulMsRYoQE+0R2iq w9ipRP9Bp38u1OMhrJIvTE5SWJX1lL0bYbCq+4MmG0KSJXgaTpkKiUyNauSMRqEy6LSM hjinYiRhvwPGBaO3JUKerxixv5qHSLAs1Rfhp72ckjXsMXlgj0hsf8kR/GuwhB3SkQKE Tl2REC0KN66PZQOxqCsmvkgIU1nUAVa0kw+hDNoVKD60z+6wacd/CUo+Mz7bixx5KFVj yXwg== X-Gm-Message-State: AOAM532v6FjGiv95BmNfb1KVOiXdBihZ8OOvFCMADl0RwwMCDudwgu6A /8XKTQ6FOXTX3PDmiKheyejFskkCydwt9ht5IGOxNJ+hk+Y4rsAAAuG6HqGv2pONHcVQIRNu1wm Y4lYuliYd1mXR/dv8DVKH9QBeBk99KWjCBeBr1qPcCHBG X-Received: by 2002:a17:907:3e0a:: with SMTP id hp10mr5178688ejc.156.1635248012166; Tue, 26 Oct 2021 04:33:32 -0700 (PDT) X-Google-Smtp-Source: ABdhPJwk9yh1otC2FcE4T7DFXV6h0+OXQXCBzAm5yVnfRbJ0//wWZH92fSunNBiBY+8wfJj6PEUCHJI5uenfImglgdM= X-Received: by 2002:a17:907:3e0a:: with SMTP id hp10mr5178648ejc.156.1635248011842; Tue, 26 Oct 2021 04:33:31 -0700 (PDT) MIME-Version: 1.0 References: <990a894c-1806-5ab2-775e-a6f2355c2299@ghiti.fr> In-Reply-To: From: Alexandre Ghiti Date: Tue, 26 Oct 2021 13:33:20 +0200 Message-ID: Subject: Re: [PATCH] kasan: Always respect CONFIG_KASAN_STACK To: Dmitry Vyukov Cc: Alexandre ghiti , Nathan Chancellor , Palmer Dabbelt , elver@google.com, akpm@linux-foundation.org, ryabinin.a.a@gmail.com, glider@google.com, andreyknvl@gmail.com, ndesaulniers@google.com, Arnd Bergmann , kasan-dev@googlegroups.com, linux-kernel@vger.kernel.org, llvm@lists.linux.dev, linux-riscv@lists.infradead.org, Paul Walmsley , aou@eecs.berkeley.edu, linux-mm@kvack.org Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Rspamd-Queue-Id: B2DA090001BC Authentication-Results: imf29.hostedemail.com; dkim=pass header.d=canonical.com header.s=20210705 header.b=rN0uXx2t; spf=pass (imf29.hostedemail.com: domain of alexandre.ghiti@canonical.com designates 185.125.188.122 as permitted sender) smtp.mailfrom=alexandre.ghiti@canonical.com; dmarc=pass (policy=none) header.from=canonical.com X-Stat-Signature: gmb7xdafpr5p4z3ikr87pz53z19uqnrn X-Rspamd-Server: rspam06 X-HE-Tag: 1635248016-19447 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 Tue, Oct 26, 2021 at 6:48 AM Dmitry Vyukov wrote: > > On Tue, 26 Oct 2021 at 06:39, Alexandre Ghiti > wrote: > > > > Hi, > > > > On Fri, Oct 15, 2021 at 3:08 PM Alexandre ghiti wrote: > > > > > > On 10/14/21 8:31 PM, Alex Ghiti wrote: > > > > Hi Nathan, > > > > > > > > Le 14/10/2021 =C3=A0 18:55, Nathan Chancellor a =C3=A9crit : > > > >> On Fri, Oct 08, 2021 at 11:46:55AM -0700, Palmer Dabbelt wrote: > > > >>> On Thu, 23 Sep 2021 07:59:46 PDT (-0700), nathan@kernel.org wrote= : > > > >>>> On Thu, Sep 23, 2021 at 12:07:17PM +0200, Marco Elver wrote: > > > >>>>> On Wed, 22 Sept 2021 at 22:55, Nathan Chancellor > > > >>>>> wrote: > > > >>>>>> Currently, the asan-stack parameter is only passed along if > > > >>>>>> CFLAGS_KASAN_SHADOW is not empty, which requires > > > >>>>>> KASAN_SHADOW_OFFSET to > > > >>>>>> be defined in Kconfig so that the value can be checked. In RIS= C-V's > > > >>>>>> case, KASAN_SHADOW_OFFSET is not defined in Kconfig, which mea= ns > > > >>>>>> that > > > >>>>>> asan-stack does not get disabled with clang even when > > > >>>>>> CONFIG_KASAN_STACK > > > >>>>>> is disabled, resulting in large stack warnings with allmodconf= ig: > > > >>>>>> > > > >>>>>> drivers/video/fbdev/omap2/omapfb/displays/panel-lgphilips-lb03= 5q02.c:117:12: > > > >>>>>> > > > >>>>>> error: stack frame size (14400) exceeds limit (2048) in functi= on > > > >>>>>> 'lb035q02_connect' [-Werror,-Wframe-larger-than] > > > >>>>>> static int lb035q02_connect(struct omap_dss_device *dssdev) > > > >>>>>> ^ > > > >>>>>> 1 error generated. > > > >>>>>> > > > >>>>>> Ensure that the value of CONFIG_KASAN_STACK is always passed > > > >>>>>> along to > > > >>>>>> the compiler so that these warnings do not happen when > > > >>>>>> CONFIG_KASAN_STACK is disabled. > > > >>>>>> > > > >>>>>> Link: https://github.com/ClangBuiltLinux/linux/issues/1453 > > > >>>>>> References: 6baec880d7a5 ("kasan: turn off asan-stack for clan= g-8 > > > >>>>>> and earlier") > > > >>>>>> Signed-off-by: Nathan Chancellor > > > >>>>> > > > >>>>> Reviewed-by: Marco Elver > > > >>>> > > > >>>> Thanks! > > > >>>> > > > >>>>> [ Which tree are you planning to take it through? ] > > > >>>> > > > >>>> Gah, I was intending for it to go through -mm, then I cc'd neith= er > > > >>>> Andrew nor linux-mm... :/ Andrew, do you want me to resend or ca= n you > > > >>>> grab it from LKML? > > > >>> > > > >>> Acked-by: Palmer Dabbelt > > > >>> > > > >>> (assuming you still want it through somewhere else) > > > >> > > > >> Thanks, it is now in mainline as commit 19532869feb9 ("kasan: alwa= ys > > > >> respect CONFIG_KASAN_STACK"). > > > >> > > > >>>>> Note, arch/riscv/include/asm/kasan.h mentions KASAN_SHADOW_OFFS= ET in > > > >>>>> comment (copied from arm64). Did RISC-V just forget to copy ove= r the > > > >>>>> Kconfig option? > > > >>>> > > > >>>> I do see it defined in that file as well but you are right that > > > >>>> they did > > > >>>> not copy the Kconfig logic, even though it was present in the tr= ee > > > >>>> when > > > >>>> RISC-V KASAN was implemented. Perhaps they should so that they g= et > > > >>>> access to the other flags in the "else" branch? > > > >>> > > > >>> Ya, looks like we just screwed this up. I'm seeing some warnings= like > > > >>> > > > >>> cc1: warning: =E2=80=98-fsanitize=3Dkernel-address=E2=80=99 w= ith stack protection > > > >>> is not supported without =E2=80=98-fasan-shadow-offset=3D=E2=80= =99 for this target > > > >> > > > >> Hmmm, I thought I did a GCC build with this change but I must not = have > > > >> :/ > > > >> > > > >>> which is how I ended up here, I'm assuming that's what you're > > > >>> talking about > > > >>> here? LMK if you were planning on sending along a fix or if you > > > >>> want me to > > > >>> go figure it out. > > > >> > > > >> I took a look at moving the logic into Kconfig like arm64 before s= ending > > > >> this change and I did not really understand it well enough to do s= o. I > > > >> think it would be best if you were able to do that so that nothing= gets > > > >> messed up. > > > >> > > > > > > > > I'll do it tomorrow, I'm the last one who touched kasan on riscv :) > > > > > > > > > > Adding KASAN_SHADOW_OFFSET config makes kasan kernel fails to boot. > > > It receives a *write* fault at the beginning of a memblock_alloc > > > function while populating the kernel shadow memory: the trap address = is > > > in the kasan shadow virtual address range and this corresponds to a > > > kernel address in init_stack. The question is: how do I populate the > > > stack shadow mapping without using memblock API? It's weird, I don't > > > find anything on other architectures. > > > > @kasan: Any idea what we are doing wrong in riscv to encounter the > > above situation? > > Hi Alex, Palmer, > > The patch changes the definition of the KASAN_SHADOW_OFFSET const. > Does it's value change as a result or not? Have you tried to print it > before/after? > If value does not change, then this is more mysterious. If it changes, > then there lots of possible explanations (points to unmapped region, > overlaps with something), but we need to know values before/after to So I debugged a bit more what happened here, and actually the culprit is the call to kasan_populate_early_shadow at the beginning of kasan_init which write-protects the access to kasan_early_shadow_page and hence the write fault later when using memblock. I don't see the point of this call anyway since we populate swapper_pg_dir in kasan_early_init and then we write-protect the access to kasan_early_shadow_page at the end of kasan_init. But that may not be ideal, so I'm open to a better suggestion than just removing the call to kasan_populate_early_shadow. Sorry I did not dig further before asking and thanks for your time, Alex > answer this. > > > > Thanks, > > > > Alex > > > > > > > > And just a short note: I have realized this will break with the sv48 > > > patchset as we decide at runtime the address space width and the kasa= n > > > shadow start address is different between sv39 and sv48. I will have = to > > > do like x86 and move the kasan shadow start at the end of the address > > > space so that it is the same for both sv39 and sv48. > > > > > > Thanks, > > > > > > Alex > > > > > > > > > > Thanks, > > > > > > > > Alex > > > > > > > >> Cheers, > > > >> Nathan > > > >> > > > >> _______________________________________________ > > > >> linux-riscv mailing list > > > >> linux-riscv@lists.infradead.org > > > >> http://lists.infradead.org/mailman/listinfo/linux-riscv > > > >> > > > > > > > > _______________________________________________ > > > > linux-riscv mailing list > > > > linux-riscv@lists.infradead.org > > > > http://lists.infradead.org/mailman/listinfo/linux-riscv > > > > > > _______________________________________________ > > > linux-riscv mailing list > > > linux-riscv@lists.infradead.org > > > http://lists.infradead.org/mailman/listinfo/linux-riscv