dma: kmsan: unpoison DMA mappings

KMSAN doesn't know about DMA memory writes performed by devices.  We
unpoison such memory when it's mapped to avoid false positive reports.

Link: https://lkml.kernel.org/r/20220915150417.722975-22-glider@google.comSigned-off-by: Alexander Potapenko <glider@google.com>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: Alexei Starovoitov <ast@kernel.org>
Cc: Andrey Konovalov <andreyknvl@gmail.com>
Cc: Andrey Konovalov <andreyknvl@google.com>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Christoph Lameter <cl@linux.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Eric Biggers <ebiggers@google.com>
Cc: Eric Biggers <ebiggers@kernel.org>
Cc: Eric Dumazet <edumazet@google.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Herbert Xu <herbert@gondor.apana.org.au>
Cc: Ilya Leoshkevich <iii@linux.ibm.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Marco Elver <elver@google.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Michael S. Tsirkin <mst@redhat.com>
Cc: Pekka Enberg <penberg@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Petr Mladek <pmladek@suse.com>
Cc: Stephen Rothwell <sfr@canb.auug.org.au>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Vasily Gorbik <gor@linux.ibm.com>
Cc: Vegard Nossum <vegard.nossum@oracle.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

include/linux/kmsan.h

@@ -9,6 +9,7 @@
 #ifndef _LINUX_KMSAN_H
 #define _LINUX_KMSAN_H
 
+#include <linux/dma-direction.h>
 #include <linux/gfp.h>
 #include <linux/kmsan-checks.h>
 #include <linux/types.h>
@@ -16,6 +17,7 @@
 struct page;
 struct kmem_cache;
 struct task_struct;
+struct scatterlist;
 
 #ifdef CONFIG_KMSAN
 
@@ -172,6 +174,35 @@ void kmsan_ioremap_page_range(unsigned long addr, unsigned long end,
  */
 void kmsan_iounmap_page_range(unsigned long start, unsigned long end);
 
+/**
+ * kmsan_handle_dma() - Handle a DMA data transfer.
+ * @page:   first page of the buffer.
+ * @offset: offset of the buffer within the first page.
+ * @size:   buffer size.
+ * @dir:    one of possible dma_data_direction values.
+ *
+ * Depending on @direction, KMSAN:
+ * * checks the buffer, if it is copied to device;
+ * * initializes the buffer, if it is copied from device;
+ * * does both, if this is a DMA_BIDIRECTIONAL transfer.
+ */
+void kmsan_handle_dma(struct page *page, size_t offset, size_t size,
+		      enum dma_data_direction dir);
+
+/**
+ * kmsan_handle_dma_sg() - Handle a DMA transfer using scatterlist.
+ * @sg:    scatterlist holding DMA buffers.
+ * @nents: number of scatterlist entries.
+ * @dir:   one of possible dma_data_direction values.
+ *
+ * Depending on @direction, KMSAN:
+ * * checks the buffers in the scatterlist, if they are copied to device;
+ * * initializes the buffers, if they are copied from device;
+ * * does both, if this is a DMA_BIDIRECTIONAL transfer.
+ */
+void kmsan_handle_dma_sg(struct scatterlist *sg, int nents,
+			 enum dma_data_direction dir);
+
 #else
 
 static inline void kmsan_init_shadow(void)
@@ -254,6 +285,16 @@ static inline void kmsan_iounmap_page_range(unsigned long start,
 {
 }
 
+static inline void kmsan_handle_dma(struct page *page, size_t offset,
+				    size_t size, enum dma_data_direction dir)
+{
+}
+
+static inline void kmsan_handle_dma_sg(struct scatterlist *sg, int nents,
+				       enum dma_data_direction dir)
+{
+}
+
 #endif
 
 #endif /* _LINUX_KMSAN_H */

kernel/dma/mapping.c

@@ -10,6 +10,7 @@
 #include <linux/dma-map-ops.h>
 #include <linux/export.h>
 #include <linux/gfp.h>
+#include <linux/kmsan.h>
 #include <linux/of_device.h>
 #include <linux/slab.h>
 #include <linux/vmalloc.h>
@@ -156,6 +157,7 @@ dma_addr_t dma_map_page_attrs(struct device *dev, struct page *page,
 		addr = dma_direct_map_page(dev, page, offset, size, dir, attrs);
 	else
 		addr = ops->map_page(dev, page, offset, size, dir, attrs);
+	kmsan_handle_dma(page, offset, size, dir);
 	debug_dma_map_page(dev, page, offset, size, dir, addr, attrs);
 
 	return addr;
@@ -194,11 +196,13 @@ static int __dma_map_sg_attrs(struct device *dev, struct scatterlist *sg,
 	else
 		ents = ops->map_sg(dev, sg, nents, dir, attrs);
 
-	if (ents > 0)
+	if (ents > 0) {
+		kmsan_handle_dma_sg(sg, nents, dir);
 		debug_dma_map_sg(dev, sg, nents, ents, dir, attrs);
-	else if (WARN_ON_ONCE(ents != -EINVAL && ents != -ENOMEM &&
-			      ents != -EIO && ents != -EREMOTEIO))
+	} else if (WARN_ON_ONCE(ents != -EINVAL && ents != -ENOMEM &&
+				ents != -EIO && ents != -EREMOTEIO)) {
 		return -EIO;
+	}
 
 	return ents;
 }

mm/kmsan/hooks.c

@@ -10,10 +10,12 @@
  */
 
 #include <linux/cacheflush.h>
+#include <linux/dma-direction.h>
 #include <linux/gfp.h>
 #include <linux/kmsan.h>
 #include <linux/mm.h>
 #include <linux/mm_types.h>
+#include <linux/scatterlist.h>
 #include <linux/slab.h>
 #include <linux/uaccess.h>
 
@@ -243,6 +245,63 @@ void kmsan_copy_to_user(void __user *to, const void *from, size_t to_copy,
 }
 EXPORT_SYMBOL(kmsan_copy_to_user);
 
+static void kmsan_handle_dma_page(const void *addr, size_t size,
+				  enum dma_data_direction dir)
+{
+	switch (dir) {
+	case DMA_BIDIRECTIONAL:
+		kmsan_internal_check_memory((void *)addr, size, /*user_addr*/ 0,
+					    REASON_ANY);
+		kmsan_internal_unpoison_memory((void *)addr, size,
+					       /*checked*/ false);
+		break;
+	case DMA_TO_DEVICE:
+		kmsan_internal_check_memory((void *)addr, size, /*user_addr*/ 0,
+					    REASON_ANY);
+		break;
+	case DMA_FROM_DEVICE:
+		kmsan_internal_unpoison_memory((void *)addr, size,
+					       /*checked*/ false);
+		break;
+	case DMA_NONE:
+		break;
+	}
+}
+
+/* Helper function to handle DMA data transfers. */
+void kmsan_handle_dma(struct page *page, size_t offset, size_t size,
+		      enum dma_data_direction dir)
+{
+	u64 page_offset, to_go, addr;
+
+	if (PageHighMem(page))
+		return;
+	addr = (u64)page_address(page) + offset;
+	/*
+	 * The kernel may occasionally give us adjacent DMA pages not belonging
+	 * to the same allocation. Process them separately to avoid triggering
+	 * internal KMSAN checks.
+	 */
+	while (size > 0) {
+		page_offset = addr % PAGE_SIZE;
+		to_go = min(PAGE_SIZE - page_offset, (u64)size);
+		kmsan_handle_dma_page((void *)addr, to_go, dir);
+		addr += to_go;
+		size -= to_go;
+	}
+}
+
+void kmsan_handle_dma_sg(struct scatterlist *sg, int nents,
+			 enum dma_data_direction dir)
+{
+	struct scatterlist *item;
+	int i;
+
+	for_each_sg(sg, item, nents, i)
+		kmsan_handle_dma(sg_page(item), item->offset, item->length,
+				 dir);
+}
+
 /* Functions from kmsan-checks.h follow. */
 void kmsan_poison_memory(const void *address, size_t size, gfp_t flags)
 {