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Wed, 26 May 2021 04:28:03 -0700 (PDT) MIME-Version: 1.0 References: <20210525130043.186290-1-gerald.schaefer@linux.ibm.com> <20210525130043.186290-2-gerald.schaefer@linux.ibm.com> In-Reply-To: <20210525130043.186290-2-gerald.schaefer@linux.ibm.com> From: Anatoly Pugachev Date: Wed, 26 May 2021 14:27:52 +0300 Message-ID: Subject: Re: [PATCH 1/1] mm/debug_vm_pgtable: fix alignment for pmd/pud_advanced_tests() To: Gerald Schaefer Cc: Andrew Morton , Anshuman Khandual , linux-mm , LKML , linux-arch , linux-sparc , linux-s390 , stable@vger.kernel.org Content-Type: text/plain; charset="UTF-8" X-Rspamd-Queue-Id: C2FD120007E0 Authentication-Results: imf18.hostedemail.com; dkim=pass header.d=gmail.com header.s=20161025 header.b="D/enDesM"; dmarc=pass (policy=none) header.from=gmail.com; spf=pass (imf18.hostedemail.com: domain of matorola@gmail.com designates 209.85.219.173 as permitted sender) smtp.mailfrom=matorola@gmail.com X-Rspamd-Server: rspam03 X-Stat-Signature: ddfbkj4z4fzu8mxzcsuef8k3gyam4cf3 X-HE-Tag: 1622028477-188516 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, May 25, 2021 at 4:03 PM Gerald Schaefer wrote: > > In pmd/pud_advanced_tests(), the vaddr is aligned up to the next pmd/pud > entry, and so it does not match the given pmdp/pudp and (aligned down) pfn > any more. > > For s390, this results in memory corruption, because the IDTE instruction > used e.g. in xxx_get_and_clear() will take the vaddr for some calculations, > in combination with the given pmdp. It will then end up with a wrong table > origin, ending on ...ff8, and some of those wrongly set low-order bits will > also select a wrong pagetable level for the index addition. IDTE could > therefore invalidate (or 0x20) something outside of the page tables, > depending on the wrongly picked index, which in turn depends on the random > vaddr. > > As result, we sometimes see "BUG task_struct (Not tainted): Padding > overwritten" on s390, where one 0x5a padding value got overwritten with > 0x7a. > > Fix this by aligning down, similar to how the pmd/pud_aligned pfns are > calculated. > > Fixes: a5c3b9ffb0f40 ("mm/debug_vm_pgtable: add tests validating advanced arch page table helpers") > Cc: # v5.9+ > Signed-off-by: Gerald Schaefer boot tested on sparc64 with quick run of stress-ng ( --class memory --sequential -1 --timeout 10s -v --pathological --oomable --metrics-brief ) stress-ng: debug: [371408] system: Linux ttip 5.13.0-rc3-00043-gad9f25d33860-dirty #218 SMP Wed May 26 11:55:54 MSK 2021 sparc64 Tested-by: Anatoly Pugachev