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[174.169.122.120]) by smtp.gmail.com with ESMTPSA id 6a1803df08f44-6dd181c0fbasm19229356d6.94.2024.12.20.10.20.23 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 20 Dec 2024 10:20:24 -0800 (PST) Date: Fri, 20 Dec 2024 13:20:20 -0500 From: Rafael Aquini To: Matthew Wilcox Cc: Audra Mitchell , linux-mm@kvack.org, aris@redhat.com, akpm@linux-foundation.org, william.kucharski@oracle.com, linux-kernel@vger.kernel.org Subject: Re: [PATCH] mm: Stop PMD alignment for PIE shared objects Message-ID: References: <20241219211552.1450226-1-audra@redhat.com> MIME-Version: 1.0 In-Reply-To: X-Mimecast-Spam-Score: 0 X-Mimecast-MFC-PROC-ID: AX8LHw4mbriajHtk_A0u3rCCMe8PZoWXyYn5tyKlpvQ_1734718825 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=us-ascii Content-Disposition: inline X-Rspamd-Queue-Id: 02D9340017 X-Rspamd-Server: rspam12 X-Stat-Signature: yqerzf4u73sen5gp1qp17xtg78b1i5kt X-Rspam-User: X-HE-Tag: 1734718796-574451 X-HE-Meta: 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 5KtP2dJp iNODda9GaRe5KyMqJJSE1M5ly72++s0hy/1N0I6xP7s9gnOiO/20YNCJG39y8W2DaOe/kPLjTgc0lo0/t9M1g4TO8l+mVCpJjfKRTIXm97JACbro9jPk5ppFoId+upjmhhP0Srgk5I7eP0BaXxZvsOS6jl6vYCR9BweNsPhUGERgTDLVn1JLkJeiBp/TLuKkjNnQUQX2hCcfv5xZMAxAWdUX7esvcehZeSaMUIu+vyzB51R0CFWRxzd27oa8RIpovFSrcgB8ndlmRTLwoHOylgVPjD3wXlxs5uU+YuxXSLuh2JeZVOqgZ7/oFy7pMmxSgp7euiUn4jPf8PSGQVIMLpSKdg9/g/RbC+HlKwBmQ4M5FEJMe8nyK9tuR8FvHghyOv1ctM8fwFhhUp79bqvFEYoeGLw== X-Bogosity: Ham, tests=bogofilter, spamicity=0.048185, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Thu, Dec 19, 2024 at 09:30:58PM +0000, Matthew Wilcox wrote: > On Thu, Dec 19, 2024 at 04:15:52PM -0500, Audra Mitchell wrote: > > After commit 1854bc6e2420 ("mm/readahead: Align file mappings for non-DAX") > > any request through thp_get_unmapped_area would align to a PMD_SIZE, > > causing shared objects to have less randomization than previously (9 less > > bits for 2MB PMDs). As these lower 9 bits are the most impactful for > > ASLR, this change could be argued to have an impact on security. > > Yes, very tiresome people have been making that argument for a long > time. Do you have anything further to add to the discussion that > happened here: > > https://lore.kernel.org/linux-mm/20240118133504.2910955-1-shy828301@gmail.com/ > > particularly in light of 3afb76a66b55 existing. > Linus, however, disliked the config question and ended up reverting 3afb76a66b55 a while after.