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[80.71.142.58]) by smtp.gmail.com with ESMTPSA id n19-20020a509353000000b004aacec09ca6sm163389eda.42.2023.02.15.18.08.53 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 15 Feb 2023 18:08:53 -0800 (PST) Date: Thu, 16 Feb 2023 03:08:21 +0100 (CET) From: Jesper Juhl To: Mike Kravetz cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, Muchun Song , Andi Kleen , Sasha Levin , Anders Roxell , Andrew Morton , Naresh Kamboju , stable@vger.kernel.org Subject: Re: [PATCH] hugetlb: check for undefined shift on 32 bit architectures In-Reply-To: <20230216013542.138708-1-mike.kravetz@oracle.com> Message-ID: References: <20230216013542.138708-1-mike.kravetz@oracle.com> User-Agent: Alpine 2.26 (LNX 649 2022-06-02) MIME-Version: 1.0 Content-Type: text/plain; format=flowed; charset=US-ASCII X-Rspamd-Server: rspam07 X-Rspamd-Queue-Id: B6C98C0012 X-Rspam-User: X-Stat-Signature: bzerenumqbnstt9ijpnjghduycna8iib X-HE-Tag: 1676513335-136032 X-HE-Meta: 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 fL2CRvNM 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 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 Wed, 15 Feb 2023, Mike Kravetz wrote: > Users can specify the hugetlb page size in the mmap, shmget and > memfd_create system calls. This is done by using 6 bits within the > flags argument to encode the base-2 logarithm of the desired page size. > The routine hstate_sizelog() uses the log2 value to find the > corresponding hugetlb hstate structure. Converting the log2 value > (page_size_log) to potential hugetlb page size is the simple statement: > > 1UL << page_size_log > > Because only 6 bits are used for page_size_log, the left shift can not > be greater than 63. This is fine on 64 bit architectures where a long > is 64 bits. However, if a value greater than 31 is passed on a 32 bit > architecture (where long is 32 bits) the shift will result in undefined > behavior. This was generally not an issue as the result of the > undefined shift had to exactly match hugetlb page size to proceed. > > Recent improvements in runtime checking have resulted in this undefined > behavior throwing errors such as reported below. > > Fix by comparing page_size_log to BITS_PER_LONG before doing shift. > > Reported-by: Naresh Kamboju > Link: https://lore.kernel.org/lkml/CA+G9fYuei_Tr-vN9GS7SfFyU1y9hNysnf=PB7kT0=yv4MiPgVg@mail.gmail.com/ > Fixes: 42d7395feb56 ("mm: support more pagesizes for MAP_HUGETLB/SHM_HUGETLB") > Cc: > Signed-off-by: Mike Kravetz Looks good to me. Reviewed-by: Jesper Juhl