linux-kernel - [PATCH v3 42/46] x86: kmsan: sync metadata pages on page fault

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Message-Id: <20220426164315.625149-43-glider@google.com>
Date:   Tue, 26 Apr 2022 18:43:11 +0200
From:   Alexander Potapenko <glider@...gle.com>
To:     glider@...gle.com
Cc:     Alexander Viro <viro@...iv.linux.org.uk>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Andrey Konovalov <andreyknvl@...gle.com>,
        Andy Lutomirski <luto@...nel.org>,
        Arnd Bergmann <arnd@...db.de>, Borislav Petkov <bp@...en8.de>,
        Christoph Hellwig <hch@....de>,
        Christoph Lameter <cl@...ux.com>,
        David Rientjes <rientjes@...gle.com>,
        Dmitry Vyukov <dvyukov@...gle.com>,
        Eric Dumazet <edumazet@...gle.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Herbert Xu <herbert@...dor.apana.org.au>,
        Ilya Leoshkevich <iii@...ux.ibm.com>,
        Ingo Molnar <mingo@...hat.com>, Jens Axboe <axboe@...nel.dk>,
        Joonsoo Kim <iamjoonsoo.kim@....com>,
        Kees Cook <keescook@...omium.org>,
        Marco Elver <elver@...gle.com>,
        Mark Rutland <mark.rutland@....com>,
        Matthew Wilcox <willy@...radead.org>,
        "Michael S. Tsirkin" <mst@...hat.com>,
        Pekka Enberg <penberg@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Petr Mladek <pmladek@...e.com>,
        Steven Rostedt <rostedt@...dmis.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Vasily Gorbik <gor@...ux.ibm.com>,
        Vegard Nossum <vegard.nossum@...cle.com>,
        Vlastimil Babka <vbabka@...e.cz>, kasan-dev@...glegroups.com,
        linux-mm@...ck.org, linux-arch@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: [PATCH v3 42/46] x86: kmsan: sync metadata pages on page fault

KMSAN assumes shadow and origin pages for every allocated page are
accessible. For pages between [VMALLOC_START, VMALLOC_END] those metadata
pages start at KMSAN_VMALLOC_SHADOW_START and
KMSAN_VMALLOC_ORIGIN_START, therefore we must sync a bigger memory
region.

Signed-off-by: Alexander Potapenko <glider@...gle.com>

---

v2:
 -- addressed reports from kernel test robot <lkp@...el.com>

Link: https://linux-review.googlesource.com/id/Ia5bd541e54f1ecc11b86666c3ec87c62ac0bdfb8
---
 arch/x86/mm/fault.c | 23 ++++++++++++++++++++++-
 1 file changed, 22 insertions(+), 1 deletion(-)

diff --git a/arch/x86/mm/fault.c b/arch/x86/mm/fault.c
index d0074c6ed31a3..f2250a32a10ca 100644
--- a/arch/x86/mm/fault.c
+++ b/arch/x86/mm/fault.c
@@ -260,7 +260,7 @@ static noinline int vmalloc_fault(unsigned long address)
 }
 NOKPROBE_SYMBOL(vmalloc_fault);
 
-void arch_sync_kernel_mappings(unsigned long start, unsigned long end)
+static void __arch_sync_kernel_mappings(unsigned long start, unsigned long end)
 {
 	unsigned long addr;
 
@@ -284,6 +284,27 @@ void arch_sync_kernel_mappings(unsigned long start, unsigned long end)
 	}
 }
 
+void arch_sync_kernel_mappings(unsigned long start, unsigned long end)
+{
+	__arch_sync_kernel_mappings(start, end);
+#ifdef CONFIG_KMSAN
+	/*
+	 * KMSAN maintains two additional metadata page mappings for the
+	 * [VMALLOC_START, VMALLOC_END) range. These mappings start at
+	 * KMSAN_VMALLOC_SHADOW_START and KMSAN_VMALLOC_ORIGIN_START and
+	 * have to be synced together with the vmalloc memory mapping.
+	 */
+	if (start >= VMALLOC_START && end < VMALLOC_END) {
+		__arch_sync_kernel_mappings(
+			start - VMALLOC_START + KMSAN_VMALLOC_SHADOW_START,
+			end - VMALLOC_START + KMSAN_VMALLOC_SHADOW_START);
+		__arch_sync_kernel_mappings(
+			start - VMALLOC_START + KMSAN_VMALLOC_ORIGIN_START,
+			end - VMALLOC_START + KMSAN_VMALLOC_ORIGIN_START);
+	}
+#endif
+}
+
 static bool low_pfn(unsigned long pfn)
 {
 	return pfn < max_low_pfn;
-- 
2.36.0.rc2.479.g8af0fa9b8e-goog