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[46.139.12.213]) by smtp.gmail.com with ESMTPSA id h125sm147104wmf.31.2019.08.28.11.58.33 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 28 Aug 2019 11:58:34 -0700 (PDT) Date: Wed, 28 Aug 2019 20:58:32 +0200 From: Ingo Molnar To: Thomas Gleixner Cc: LKML , x86@kernel.org, Song Liu , Joerg Roedel , Dave Hansen , Andy Lutomirski , Peter Zijlstra , Rik van Riel Subject: Re: [patch 1/2] x86/mm/pti: Handle unaligned address gracefully in pti_clone_pagetable() Message-ID: <20190828185832.GA77809@gmail.com> References: <20190828142445.454151604@linutronix.de> <20190828143123.971884723@linutronix.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190828143123.971884723@linutronix.de> User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org * Thomas Gleixner wrote: > From: Song Liu > > pti_clone_pmds() assumes that the supplied address is either: > > - properly PUD/PMD aligned > or > - the address is actually mapped which means that independent > of the mapping level (PUD/PMD/PTE) the next higher mapping > exist. s/independent /independently s/exist /exists > If that's not the case the unaligned address can be incremented by PUD or > PMD size wrongly. All callers supply mapped and/or aligned addresses, but > for robustness sake, it's better to handle that case proper and to emit a > warning. s/wrongly /incorrectly s/robustness sake /robustness's sake s/proper /properly With that: > pud = pud_offset(p4d, addr); > if (pud_none(*pud)) { > - addr += PUD_SIZE; > + WARN_ON_ONCE(addr & PUD_MASK); > + addr = round_up(addr + 1, PUD_SIZE); > continue; > } > > pmd = pmd_offset(pud, addr); > if (pmd_none(*pmd)) { > - addr += PMD_SIZE; > + WARN_ON_ONCE(addr & PMD_MASK); > + addr = round_up(addr + 1, PMD_SIZE); So given that PUD_MASK and PMD_MASK are masking out the *offset*: arch/x86/include/asm/pgtable_64_types.h:#define PMD_MASK (~(PMD_SIZE - 1)) Didn't we want something like: WARN_ON_ONCE(addr & ~PUD_MASK); WARN_ON_ONCE(addr & ~PMD_MASK); to warn about an unaligned 'addr', or am I misreading the intent here? Thanks, Ingo