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[46.139.12.213]) by smtp.gmail.com with ESMTPSA id r15sm476059wrj.68.2019.08.28.16.22.34 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 28 Aug 2019 16:22:35 -0700 (PDT) Date: Thu, 29 Aug 2019 01:22:33 +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 V3 1/2] x86/mm/pti: Handle unaligned address gracefully in pti_clone_pagetable() Message-ID: <20190828232233.GA99597@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: 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 independently > of the mapping level (PUD/PMD/PTE) the next higher mapping > exists. > > If that's not the case the unaligned address can be incremented by PUD or > PMD size incorrectly. All callers supply mapped and/or aligned addresses, > but for the sake of robustness it's better to handle that case properly and > to emit a warning. > > [ tglx: Rewrote changelog and added WARN_ON_ONCE() ] > > Signed-off-by: Song Liu > Signed-off-by: Thomas Gleixner > --- > V2: Negate P[UM]D_MASK for checking whether the offset part is 0 > V3: Fix changelog > --- > arch/x86/mm/pti.c | 6 ++++-- > 1 file changed, 4 insertions(+), 2 deletions(-) > > --- a/arch/x86/mm/pti.c > +++ b/arch/x86/mm/pti.c > @@ -330,13 +330,15 @@ pti_clone_pgtable(unsigned long start, u > > 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); > continue; > } Reviewed-by: Ingo Molnar Thanks, Ingo