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Received: from foss.arm.com ([217.140.110.172]) by bombadil.infradead.org with esmtp (Exim 4.94 #2 (Red Hat Linux)) id 1licQx-00Dl7m-Re for linux-arm-kernel@lists.infradead.org; Mon, 17 May 2021 12:33:26 +0000 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 346A1113E; Mon, 17 May 2021 05:33:19 -0700 (PDT) Received: from e112269-lin.arm.com (unknown [172.31.20.19]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 2CBBB3F73B; Mon, 17 May 2021 05:33:16 -0700 (PDT) From: Steven Price To: Catalin Marinas , Marc Zyngier , Will Deacon Cc: Steven Price , James Morse , Julien Thierry , Suzuki K Poulose , kvmarm@lists.cs.columbia.edu, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, Dave Martin , Mark Rutland , Thomas Gleixner , qemu-devel@nongnu.org, Juan Quintela , "Dr. David Alan Gilbert" , Richard Henderson , Peter Maydell , Haibo Xu , Andrew Jones Subject: [PATCH v12 3/8] arm64: mte: Sync tags for pages where PTE is untagged Date: Mon, 17 May 2021 13:32:34 +0100 Message-Id: <20210517123239.8025-4-steven.price@arm.com> X-Mailer: git-send-email 2.20.1 In-Reply-To: <20210517123239.8025-1-steven.price@arm.com> References: <20210517123239.8025-1-steven.price@arm.com> MIME-Version: 1.0 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20210517_053320_014641_DE6AB1E9 X-CRM114-Status: GOOD ( 16.44 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org A KVM guest could store tags in a page even if the VMM hasn't mapped the page with PROT_MTE. So when restoring pages from swap we will need to check to see if there are any saved tags even if !pte_tagged(). However don't check pages for which pte_access_permitted() returns false as these will not have been swapped out. Signed-off-by: Steven Price --- arch/arm64/include/asm/pgtable.h | 9 +++++++-- arch/arm64/kernel/mte.c | 16 ++++++++++++++-- 2 files changed, 21 insertions(+), 4 deletions(-) diff --git a/arch/arm64/include/asm/pgtable.h b/arch/arm64/include/asm/pgtable.h index 0b10204e72fc..275178a810c1 100644 --- a/arch/arm64/include/asm/pgtable.h +++ b/arch/arm64/include/asm/pgtable.h @@ -314,8 +314,13 @@ static inline void set_pte_at(struct mm_struct *mm, unsigned long addr, if (pte_present(pte) && pte_user_exec(pte) && !pte_special(pte)) __sync_icache_dcache(pte); - if (system_supports_mte() && - pte_present(pte) && pte_tagged(pte) && !pte_special(pte)) + /* + * If the PTE would provide user space access to the tags associated + * with it then ensure that the MTE tags are synchronised. Exec-only + * mappings don't expose tags (instruction fetches don't check tags). + */ + if (system_supports_mte() && pte_present(pte) && + pte_access_permitted(pte, false) && !pte_special(pte)) mte_sync_tags(ptep, pte); __check_racy_pte_update(mm, ptep, pte); diff --git a/arch/arm64/kernel/mte.c b/arch/arm64/kernel/mte.c index c88e778c2fa9..a604818c52c1 100644 --- a/arch/arm64/kernel/mte.c +++ b/arch/arm64/kernel/mte.c @@ -33,11 +33,15 @@ DEFINE_STATIC_KEY_FALSE(mte_async_mode); EXPORT_SYMBOL_GPL(mte_async_mode); #endif -static void mte_sync_page_tags(struct page *page, pte_t *ptep, bool check_swap) +static void mte_sync_page_tags(struct page *page, pte_t *ptep, bool check_swap, + bool pte_is_tagged) { unsigned long flags; pte_t old_pte = READ_ONCE(*ptep); + if (!is_swap_pte(old_pte) && !pte_is_tagged) + return; + spin_lock_irqsave(&tag_sync_lock, flags); /* Recheck with the lock held */ @@ -53,6 +57,9 @@ static void mte_sync_page_tags(struct page *page, pte_t *ptep, bool check_swap) } } + if (!pte_is_tagged) + goto out; + page_kasan_tag_reset(page); /* * We need smp_wmb() in between setting the flags and clearing the @@ -76,10 +83,15 @@ void mte_sync_tags(pte_t *ptep, pte_t pte) bool check_swap = nr_pages == 1; bool pte_is_tagged = pte_tagged(pte); + /* Early out if there's nothing to do */ + if (!check_swap && !pte_is_tagged) + return; + /* if PG_mte_tagged is set, tags have already been initialised */ for (i = 0; i < nr_pages; i++, page++) { if (!test_bit(PG_mte_tagged, &page->flags)) - mte_sync_page_tags(page, ptep, check_swap); + mte_sync_page_tags(page, ptep, check_swap, + pte_is_tagged); } } -- 2.20.1 _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel