1 files changed, 147 insertions, 88 deletions

diff --git a/mm/vmalloc.c b/mm/vmalloc.c
index 978194dc2bb8..5291c6f02cf7 100644
--- a/mm/vmalloc.c
+++ b/mm/vmalloc.c
@@ -33,11 +33,11 @@
 #include <linux/compiler.h>
 #include <linux/memcontrol.h>
 #include <linux/llist.h>
+#include <linux/uio.h>
 #include <linux/bitops.h>
 #include <linux/rbtree_augmented.h>
 #include <linux/overflow.h>
 #include <linux/pgtable.h>
-#include <linux/uaccess.h>
 #include <linux/hugetlb.h>
 #include <linux/sched/mm.h>
 #include <asm/tlbflush.h>
@@ -3442,62 +3442,96 @@ void *vmalloc_32_user(unsigned long size)
 EXPORT_SYMBOL(vmalloc_32_user);
 
 /*
- * small helper routine , copy contents to buf from addr.
- * If the page is not present, fill zero.
+ * Atomically zero bytes in the iterator.
+ *
+ * Returns the number of zeroed bytes.
  */
+static size_t zero_iter(struct iov_iter *iter, size_t count)
+{
+	size_t remains = count;
+
+	while (remains > 0) {
+		size_t num, copied;
+
+		num = remains < PAGE_SIZE ? remains : PAGE_SIZE;
+		copied = copy_page_to_iter_nofault(ZERO_PAGE(0), 0, num, iter);
+		remains -= copied;
+
+		if (copied < num)
+			break;
+	}
 
-static int aligned_vread(char *buf, char *addr, unsigned long count)
+	return count - remains;
+}
+
+/*
+ * small helper routine, copy contents to iter from addr.
+ * If the page is not present, fill zero.
+ *
+ * Returns the number of copied bytes.
+ */
+static size_t aligned_vread_iter(struct iov_iter *iter,
+				 const char *addr, size_t count)
 {
-	struct page *p;
-	int copied = 0;
+	size_t remains = count;
+	struct page *page;
 
-	while (count) {
+	while (remains > 0) {
 		unsigned long offset, length;
+		size_t copied = 0;
 
 		offset = offset_in_page(addr);
 		length = PAGE_SIZE - offset;
-		if (length > count)
-			length = count;
-		p = vmalloc_to_page(addr);
+		if (length > remains)
+			length = remains;
+		page = vmalloc_to_page(addr);
 		/*
-		 * To do safe access to this _mapped_ area, we need
-		 * lock. But adding lock here means that we need to add
-		 * overhead of vmalloc()/vfree() calls for this _debug_
-		 * interface, rarely used. Instead of that, we'll use
-		 * kmap() and get small overhead in this access function.
+		 * To do safe access to this _mapped_ area, we need lock. But
+		 * adding lock here means that we need to add overhead of
+		 * vmalloc()/vfree() calls for this _debug_ interface, rarely
+		 * used. Instead of that, we'll use an local mapping via
+		 * copy_page_to_iter_nofault() and accept a small overhead in
+		 * this access function.
 		 */
-		if (p) {
-			/* We can expect USER0 is not used -- see vread() */
-			void *map = kmap_atomic(p);
-			memcpy(buf, map + offset, length);
-			kunmap_atomic(map);
-		} else
-			memset(buf, 0, length);
+		if (page)
+			copied = copy_page_to_iter_nofault(page, offset,
+							   length, iter);
+		else
+			copied = zero_iter(iter, length);
 
-		addr += length;
-		buf += length;
-		copied += length;
-		count -= length;
+		addr += copied;
+		remains -= copied;
+
+		if (copied != length)
+			break;
 	}
-	return copied;
+
+	return count - remains;
 }
 
-static void vmap_ram_vread(char *buf, char *addr, int count, unsigned long flags)
+/*
+ * Read from a vm_map_ram region of memory.
+ *
+ * Returns the number of copied bytes.
+ */
+static size_t vmap_ram_vread_iter(struct iov_iter *iter, const char *addr,
+				  size_t count, unsigned long flags)
 {
 	char *start;
 	struct vmap_block *vb;
 	unsigned long offset;
-	unsigned int rs, re, n;
+	unsigned int rs, re;
+	size_t remains, n;
 
 	/*
 	 * If it's area created by vm_map_ram() interface directly, but
 	 * not further subdividing and delegating management to vmap_block,
 	 * handle it here.
 	 */
-	if (!(flags & VMAP_BLOCK)) {
-		aligned_vread(buf, addr, count);
-		return;
-	}
+	if (!(flags & VMAP_BLOCK))
+		return aligned_vread_iter(iter, addr, count);
+
+	remains = count;
 
 	/*
 	 * Area is split into regions and tracked with vmap_block, read out
@@ -3505,50 +3539,64 @@ static void vmap_ram_vread(char *buf, char *addr, int count, unsigned long flags
 	 */
 	vb = xa_load(&vmap_blocks, addr_to_vb_idx((unsigned long)addr));
 	if (!vb)
-		goto finished;
+		goto finished_zero;
 
 	spin_lock(&vb->lock);
 	if (bitmap_empty(vb->used_map, VMAP_BBMAP_BITS)) {
 		spin_unlock(&vb->lock);
-		goto finished;
+		goto finished_zero;
 	}
+
 	for_each_set_bitrange(rs, re, vb->used_map, VMAP_BBMAP_BITS) {
-		if (!count)
-			break;
+		size_t copied;
+
+		if (remains == 0)
+			goto finished;
+
 		start = vmap_block_vaddr(vb->va->va_start, rs);
-		while (addr < start) {
-			if (count == 0)
-				goto unlock;
-			*buf = '\0';
-			buf++;
-			addr++;
-			count--;
+
+		if (addr < start) {
+			size_t to_zero = min_t(size_t, start - addr, remains);
+			size_t zeroed = zero_iter(iter, to_zero);
+
+			addr += zeroed;
+			remains -= zeroed;
+
+			if (remains == 0 || zeroed != to_zero)
+				goto finished;
 		}
+
 		/*it could start reading from the middle of used region*/
 		offset = offset_in_page(addr);
 		n = ((re - rs + 1) << PAGE_SHIFT) - offset;
-		if (n > count)
-			n = count;
-		aligned_vread(buf, start+offset, n);
+		if (n > remains)
+			n = remains;
+
+		copied = aligned_vread_iter(iter, start + offset, n);
 
-		buf += n;
-		addr += n;
-		count -= n;
+		addr += copied;
+		remains -= copied;
+
+		if (copied != n)
+			goto finished;
 	}
-unlock:
+
 	spin_unlock(&vb->lock);
 
-finished:
+finished_zero:
 	/* zero-fill the left dirty or free regions */
-	if (count)
-		memset(buf, 0, count);
+	return count - remains + zero_iter(iter, remains);
+finished:
+	/* We couldn't copy/zero everything */
+	spin_unlock(&vb->lock);
+	return count - remains;
 }
 
 /**
- * vread() - read vmalloc area in a safe way.
- * @buf:     buffer for reading data
- * @addr:    vm address.
- * @count:   number of bytes to be read.
+ * vread_iter() - read vmalloc area in a safe way to an iterator.
+ * @iter:         the iterator to which data should be written.
+ * @addr:         vm address.
+ * @count:        number of bytes to be read.
  *
  * This function checks that addr is a valid vmalloc'ed area, and
  * copy data from that area to a given buffer. If the given memory range
@@ -3568,13 +3616,12 @@ finished:
  * (same number as @count) or %0 if [addr...addr+count) doesn't
  * include any intersection with valid vmalloc area
  */
-long vread(char *buf, char *addr, unsigned long count)
+long vread_iter(struct iov_iter *iter, const char *addr, size_t count)
 {
 	struct vmap_area *va;
 	struct vm_struct *vm;
-	char *vaddr, *buf_start = buf;
-	unsigned long buflen = count;
-	unsigned long n, size, flags;
+	char *vaddr;
+	size_t n, size, flags, remains;
 
 	addr = kasan_reset_tag(addr);
 
@@ -3582,18 +3629,22 @@ long vread(char *buf, char *addr, unsigned long count)
 	if ((unsigned long) addr + count < count)
 		count = -(unsigned long) addr;
 
+	remains = count;
+
 	spin_lock(&vmap_area_lock);
 	va = find_vmap_area_exceed_addr((unsigned long)addr);
 	if (!va)
-		goto finished;
+		goto finished_zero;
 
 	/* no intersects with alive vmap_area */
-	if ((unsigned long)addr + count <= va->va_start)
-		goto finished;
+	if ((unsigned long)addr + remains <= va->va_start)
+		goto finished_zero;
 
 	list_for_each_entry_from(va, &vmap_area_list, list) {
-		if (!count)
-			break;
+		size_t copied;
+
+		if (remains == 0)
+			goto finished;
 
 		vm = va->vm;
 		flags = va->flags & VMAP_FLAGS_MASK;
@@ -3608,6 +3659,7 @@ long vread(char *buf, char *addr, unsigned long count)
 
 		if (vm && (vm->flags & VM_UNINITIALIZED))
 			continue;
+
 		/* Pair with smp_wmb() in clear_vm_uninitialized_flag() */
 		smp_rmb();
 
@@ -3616,38 +3668,45 @@ long vread(char *buf, char *addr, unsigned long count)
 
 		if (addr >= vaddr + size)
 			continue;
-		while (addr < vaddr) {
-			if (count == 0)
+
+		if (addr < vaddr) {
+			size_t to_zero = min_t(size_t, vaddr - addr, remains);
+			size_t zeroed = zero_iter(iter, to_zero);
+
+			addr += zeroed;
+			remains -= zeroed;
+
+			if (remains == 0 || zeroed != to_zero)
 				goto finished;
-			*buf = '\0';
-			buf++;
-			addr++;
-			count--;
 		}
+
 		n = vaddr + size - addr;
-		if (n > count)
-			n = count;
+		if (n > remains)
+			n = remains;
 
 		if (flags & VMAP_RAM)
-			vmap_ram_vread(buf, addr, n, flags);
+			copied = vmap_ram_vread_iter(iter, addr, n, flags);
 		else if (!(vm->flags & VM_IOREMAP))
-			aligned_vread(buf, addr, n);
+			copied = aligned_vread_iter(iter, addr, n);
 		else /* IOREMAP area is treated as memory hole */
-			memset(buf, 0, n);
-		buf += n;
-		addr += n;
-		count -= n;
+			copied = zero_iter(iter, n);
+
+		addr += copied;
+		remains -= copied;
+
+		if (copied != n)
+			goto finished;
 	}
-finished:
-	spin_unlock(&vmap_area_lock);
 
-	if (buf == buf_start)
-		return 0;
+finished_zero:
+	spin_unlock(&vmap_area_lock);
 	/* zero-fill memory holes */
-	if (buf != buf_start + buflen)
-		memset(buf, 0, buflen - (buf - buf_start));
+	return count - remains + zero_iter(iter, remains);
+finished:
+	/* Nothing remains, or We couldn't copy/zero everything. */
+	spin_unlock(&vmap_area_lock);
 
-	return buflen;
+	return count - remains;
 }
 
 /**