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a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:sender:date:in-reply-to:message-id:mime-version :references:subject:from:to:cc; bh=utlsD1mw0rorOhWh+9V4hpftFWJXg/4VW/2wSqx9Lr0=; b=JH/xd9f2ZbP760TK25ld45HXpnE8mukbGY/Q4M5HIqOlQSLouemqxdzMSIdNynG9zV 57l3InHwrxVAP8mWntESey2MGtBKn3JAJJ5haGRgQxvGaAHCFewTSIYt/qI6TWTGasFw UJym/UAuphFzzNm7z4UUemV6k6OG1eSQRnRrz4MAhQrK3ZbEMkhclcGNPL38/f/9qPdk vCLtSxpBDxawMwOFfkrEuSSBaEPF+vXMeK/OTVSwrvuLLoF/lD8q8e2rQeluo+a4VMHS oz9K9Gzpz5sT0HcPu0leD4tCY8Eo9J9ZzrtPEUBue8R+Gap8dWDqz43byTzVRoUYRA1A EZsw== X-Gm-Message-State: AOAM531exBGPNOgvkpyMf2uc3gD0sCQ8Rih4At8cZ1FGHRvOkvcEN5hN DF/jFRZt+mdM3M44GQnoDcNgCaOndhboOZmT X-Google-Smtp-Source: ABdhPJzgONaFTZU/h3JPqsgZz6R2sgr3ZA9iJYvpwZvYvUFgReYxzWPEWMFsJd+B8VTgu3nwC5HgaPBLZj2SDWUW X-Received: from andreyknvl3.muc.corp.google.com ([2a00:79e0:15:13:7220:84ff:fe09:7e9d]) (user=andreyknvl job=sendgmr) by 2002:a7b:c84a:: with SMTP id c10mr612311wml.44.1606162168044; Mon, 23 Nov 2020 12:09:28 -0800 (PST) Date: Mon, 23 Nov 2020 21:07:50 +0100 In-Reply-To: Message-Id: <9073d4e973747a6f78d5bdd7ebe17f290d087096.1606161801.git.andreyknvl@google.com> Mime-Version: 1.0 References: X-Mailer: git-send-email 2.29.2.454.gaff20da3a2-goog Subject: [PATCH mm v11 26/42] arm64: mte: Reset the page tag in page->flags From: Andrey Konovalov To: Andrew Morton X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20201123_150933_110849_9E33340D X-CRM114-Status: GOOD ( 19.18 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: linux-arm-kernel@lists.infradead.org, Marco Elver , Catalin Marinas , Kevin Brodsky , Will Deacon , Branislav Rankov , kasan-dev@googlegroups.com, linux-kernel@vger.kernel.org, linux-mm@kvack.org, Alexander Potapenko , Evgenii Stepanov , Andrey Konovalov , Andrey Ryabinin , Vincenzo Frascino , Dmitry Vyukov 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 From: Vincenzo Frascino The hardware tag-based KASAN for compatibility with the other modes stores the tag associated to a page in page->flags. Due to this the kernel faults on access when it allocates a page with an initial tag and the user changes the tags. Reset the tag associated by the kernel to a page in all the meaningful places to prevent kernel faults on access. Note: An alternative to this approach could be to modify page_to_virt(). This though could end up being racy, in fact if a CPU checks the PG_mte_tagged bit and decides that the page is not tagged but another CPU maps the same with PROT_MTE and becomes tagged the subsequent kernel access would fail. Signed-off-by: Vincenzo Frascino Signed-off-by: Andrey Konovalov Reviewed-by: Catalin Marinas --- Change-Id: I8451d438bb63364de2a3e68041e3a27866921d4e --- arch/arm64/kernel/hibernate.c | 5 +++++ arch/arm64/kernel/mte.c | 9 +++++++++ arch/arm64/mm/copypage.c | 9 +++++++++ arch/arm64/mm/mteswap.c | 9 +++++++++ 4 files changed, 32 insertions(+) diff --git a/arch/arm64/kernel/hibernate.c b/arch/arm64/kernel/hibernate.c index 42003774d261..9c9f47e9f7f4 100644 --- a/arch/arm64/kernel/hibernate.c +++ b/arch/arm64/kernel/hibernate.c @@ -371,6 +371,11 @@ static void swsusp_mte_restore_tags(void) unsigned long pfn = xa_state.xa_index; struct page *page = pfn_to_online_page(pfn); + /* + * It is not required to invoke page_kasan_tag_reset(page) + * at this point since the tags stored in page->flags are + * already restored. + */ mte_restore_page_tags(page_address(page), tags); mte_free_tag_storage(tags); diff --git a/arch/arm64/kernel/mte.c b/arch/arm64/kernel/mte.c index 8f99c65837fd..86d554ce98b6 100644 --- a/arch/arm64/kernel/mte.c +++ b/arch/arm64/kernel/mte.c @@ -34,6 +34,15 @@ static void mte_sync_page_tags(struct page *page, pte_t *ptep, bool check_swap) return; } + page_kasan_tag_reset(page); + /* + * We need smp_wmb() in between setting the flags and clearing the + * tags because if another thread reads page->flags and builds a + * tagged address out of it, there is an actual dependency to the + * memory access, but on the current thread we do not guarantee that + * the new page->flags are visible before the tags were updated. + */ + smp_wmb(); mte_clear_page_tags(page_address(page)); } diff --git a/arch/arm64/mm/copypage.c b/arch/arm64/mm/copypage.c index 70a71f38b6a9..b5447e53cd73 100644 --- a/arch/arm64/mm/copypage.c +++ b/arch/arm64/mm/copypage.c @@ -23,6 +23,15 @@ void copy_highpage(struct page *to, struct page *from) if (system_supports_mte() && test_bit(PG_mte_tagged, &from->flags)) { set_bit(PG_mte_tagged, &to->flags); + page_kasan_tag_reset(to); + /* + * We need smp_wmb() in between setting the flags and clearing the + * tags because if another thread reads page->flags and builds a + * tagged address out of it, there is an actual dependency to the + * memory access, but on the current thread we do not guarantee that + * the new page->flags are visible before the tags were updated. + */ + smp_wmb(); mte_copy_page_tags(kto, kfrom); } } diff --git a/arch/arm64/mm/mteswap.c b/arch/arm64/mm/mteswap.c index c52c1847079c..7c4ef56265ee 100644 --- a/arch/arm64/mm/mteswap.c +++ b/arch/arm64/mm/mteswap.c @@ -53,6 +53,15 @@ bool mte_restore_tags(swp_entry_t entry, struct page *page) if (!tags) return false; + page_kasan_tag_reset(page); + /* + * We need smp_wmb() in between setting the flags and clearing the + * tags because if another thread reads page->flags and builds a + * tagged address out of it, there is an actual dependency to the + * memory access, but on the current thread we do not guarantee that + * the new page->flags are visible before the tags were updated. + */ + smp_wmb(); mte_restore_page_tags(page_address(page), tags); return true; -- 2.29.2.454.gaff20da3a2-goog _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel