Merge remote-tracking branch 'common/android-4.4' into android-4.4.y

4 files changed, 414 insertions, 29 deletions

diff --git a/mm/Makefile b/mm/Makefile
index 2ed43191fc3b..8b532c94008f 100644
--- a/mm/Makefile
+++ b/mm/Makefile
@@ -5,6 +5,9 @@
 KASAN_SANITIZE_slab_common.o := n
 KASAN_SANITIZE_slub.o := n
 
+# Since __builtin_frame_address does work as used, disable the warning.
+CFLAGS_usercopy.o += $(call cc-disable-warning, frame-address)
+
 mmu-y			:= nommu.o
 mmu-$(CONFIG_MMU)	:= gup.o highmem.o memory.o mincore.o \
 			   mlock.o mmap.o mprotect.o mremap.o msync.o rmap.o \
@@ -81,3 +84,4 @@ obj-$(CONFIG_CMA_DEBUGFS) += cma_debug.o
 obj-$(CONFIG_USERFAULTFD) += userfaultfd.o
 obj-$(CONFIG_IDLE_PAGE_TRACKING) += page_idle.o
 obj-$(CONFIG_FRAME_VECTOR) += frame_vector.o
+obj-$(CONFIG_HARDENED_USERCOPY) += usercopy.o
diff --git a/mm/slab.c b/mm/slab.c
index 4765c97ce690..24a615d42d74 100644
--- a/mm/slab.c
+++ b/mm/slab.c
@@ -4228,6 +4228,36 @@ static int __init slab_proc_init(void)
 module_init(slab_proc_init);
 #endif
 
+#ifdef CONFIG_HARDENED_USERCOPY
+/*
+ * Rejects objects that are incorrectly sized.
+ *
+ * Returns NULL if check passes, otherwise const char * to name of cache
+ * to indicate an error.
+ */
+const char *__check_heap_object(const void *ptr, unsigned long n,
+				struct page *page)
+{
+	struct kmem_cache *cachep;
+	unsigned int objnr;
+	unsigned long offset;
+
+	/* Find and validate object. */
+	cachep = page->slab_cache;
+	objnr = obj_to_index(cachep, page, (void *)ptr);
+	BUG_ON(objnr >= cachep->num);
+
+	/* Find offset within object. */
+	offset = ptr - index_to_obj(cachep, page, objnr) - obj_offset(cachep);
+
+	/* Allow address range falling entirely within object size. */
+	if (offset <= cachep->object_size && n <= cachep->object_size - offset)
+		return NULL;
+
+	return cachep->name;
+}
+#endif /* CONFIG_HARDENED_USERCOPY */
+
 /**
  * ksize - get the actual amount of memory allocated for a given object
  * @objp: Pointer to the object
diff --git a/mm/slub.c b/mm/slub.c
index 65d5f92d51d2..41f7cae64a49 100644
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -124,6 +124,14 @@ static inline int kmem_cache_debug(struct kmem_cache *s)
 #endif
 }
 
+static inline void *fixup_red_left(struct kmem_cache *s, void *p)
+{
+	if (kmem_cache_debug(s) && s->flags & SLAB_RED_ZONE)
+		p += s->red_left_pad;
+
+	return p;
+}
+
 static inline bool kmem_cache_has_cpu_partial(struct kmem_cache *s)
 {
 #ifdef CONFIG_SLUB_CPU_PARTIAL
@@ -224,24 +232,6 @@ static inline void stat(const struct kmem_cache *s, enum stat_item si)
  * 			Core slab cache functions
  *******************************************************************/
 
-/* Verify that a pointer has an address that is valid within a slab page */
-static inline int check_valid_pointer(struct kmem_cache *s,
-				struct page *page, const void *object)
-{
-	void *base;
-
-	if (!object)
-		return 1;
-
-	base = page_address(page);
-	if (object < base || object >= base + page->objects * s->size ||
-		(object - base) % s->size) {
-		return 0;
-	}
-
-	return 1;
-}
-
 static inline void *get_freepointer(struct kmem_cache *s, void *object)
 {
 	return *(void **)(object + s->offset);
@@ -271,12 +261,14 @@ static inline void set_freepointer(struct kmem_cache *s, void *object, void *fp)
 
 /* Loop over all objects in a slab */
 #define for_each_object(__p, __s, __addr, __objects) \
-	for (__p = (__addr); __p < (__addr) + (__objects) * (__s)->size;\
-			__p += (__s)->size)
+	for (__p = fixup_red_left(__s, __addr); \
+		__p < (__addr) + (__objects) * (__s)->size; \
+		__p += (__s)->size)
 
 #define for_each_object_idx(__p, __idx, __s, __addr, __objects) \
-	for (__p = (__addr), __idx = 1; __idx <= __objects;\
-			__p += (__s)->size, __idx++)
+	for (__p = fixup_red_left(__s, __addr), __idx = 1; \
+		__idx <= __objects; \
+		__p += (__s)->size, __idx++)
 
 /* Determine object index from a given position */
 static inline int slab_index(void *p, struct kmem_cache *s, void *addr)
@@ -456,6 +448,22 @@ static void get_map(struct kmem_cache *s, struct page *page, unsigned long *map)
 		set_bit(slab_index(p, s, addr), map);
 }
 
+static inline int size_from_object(struct kmem_cache *s)
+{
+	if (s->flags & SLAB_RED_ZONE)
+		return s->size - s->red_left_pad;
+
+	return s->size;
+}
+
+static inline void *restore_red_left(struct kmem_cache *s, void *p)
+{
+	if (s->flags & SLAB_RED_ZONE)
+		p -= s->red_left_pad;
+
+	return p;
+}
+
 /*
  * Debug settings:
  */
@@ -489,6 +497,26 @@ static inline void metadata_access_disable(void)
 /*
  * Object debugging
  */
+
+/* Verify that a pointer has an address that is valid within a slab page */
+static inline int check_valid_pointer(struct kmem_cache *s,
+				struct page *page, void *object)
+{
+	void *base;
+
+	if (!object)
+		return 1;
+
+	base = page_address(page);
+	object = restore_red_left(s, object);
+	if (object < base || object >= base + page->objects * s->size ||
+		(object - base) % s->size) {
+		return 0;
+	}
+
+	return 1;
+}
+
 static void print_section(char *text, u8 *addr, unsigned int length)
 {
 	metadata_access_enable();
@@ -628,7 +656,9 @@ static void print_trailer(struct kmem_cache *s, struct page *page, u8 *p)
 	pr_err("INFO: Object 0x%p @offset=%tu fp=0x%p\n\n",
 	       p, p - addr, get_freepointer(s, p));
 
-	if (p > addr + 16)
+	if (s->flags & SLAB_RED_ZONE)
+		print_section("Redzone ", p - s->red_left_pad, s->red_left_pad);
+	else if (p > addr + 16)
 		print_section("Bytes b4 ", p - 16, 16);
 
 	print_section("Object ", p, min_t(unsigned long, s->object_size,
@@ -645,9 +675,9 @@ static void print_trailer(struct kmem_cache *s, struct page *page, u8 *p)
 	if (s->flags & SLAB_STORE_USER)
 		off += 2 * sizeof(struct track);
 
-	if (off != s->size)
+	if (off != size_from_object(s))
 		/* Beginning of the filler is the free pointer */
-		print_section("Padding ", p + off, s->size - off);
+		print_section("Padding ", p + off, size_from_object(s) - off);
 
 	dump_stack();
 }
@@ -677,6 +707,9 @@ static void init_object(struct kmem_cache *s, void *object, u8 val)
 {
 	u8 *p = object;
 
+	if (s->flags & SLAB_RED_ZONE)
+		memset(p - s->red_left_pad, val, s->red_left_pad);
+
 	if (s->flags & __OBJECT_POISON) {
 		memset(p, POISON_FREE, s->object_size - 1);
 		p[s->object_size - 1] = POISON_END;
@@ -769,11 +802,11 @@ static int check_pad_bytes(struct kmem_cache *s, struct page *page, u8 *p)
 		/* We also have user information there */
 		off += 2 * sizeof(struct track);
 
-	if (s->size == off)
+	if (size_from_object(s) == off)
 		return 1;
 
 	return check_bytes_and_report(s, page, p, "Object padding",
-				p + off, POISON_INUSE, s->size - off);
+			p + off, POISON_INUSE, size_from_object(s) - off);
 }
 
 /* Check the pad bytes at the end of a slab page */
@@ -818,6 +851,10 @@ static int check_object(struct kmem_cache *s, struct page *page,
 
 	if (s->flags & SLAB_RED_ZONE) {
 		if (!check_bytes_and_report(s, page, object, "Redzone",
+			object - s->red_left_pad, val, s->red_left_pad))
+			return 0;
+
+		if (!check_bytes_and_report(s, page, object, "Redzone",
 			endobject, val, s->inuse - s->object_size))
 			return 0;
 	} else {
@@ -1468,7 +1505,7 @@ static struct page *allocate_slab(struct kmem_cache *s, gfp_t flags, int node)
 			set_freepointer(s, p, NULL);
 	}
 
-	page->freelist = start;
+	page->freelist = fixup_red_left(s, start);
 	page->inuse = page->objects;
 	page->frozen = 1;
 
@@ -3283,7 +3320,7 @@ static int calculate_sizes(struct kmem_cache *s, int forced_order)
 		 */
 		size += 2 * sizeof(struct track);
 
-	if (flags & SLAB_RED_ZONE)
+	if (flags & SLAB_RED_ZONE) {
 		/*
 		 * Add some empty padding so that we can catch
 		 * overwrites from earlier objects rather than let
@@ -3292,6 +3329,11 @@ static int calculate_sizes(struct kmem_cache *s, int forced_order)
 		 * of the object.
 		 */
 		size += sizeof(void *);
+
+		s->red_left_pad = sizeof(void *);
+		s->red_left_pad = ALIGN(s->red_left_pad, s->align);
+		size += s->red_left_pad;
+	}
 #endif
 
 	/*
@@ -3585,6 +3627,46 @@ void *__kmalloc_node(size_t size, gfp_t flags, int node)
 EXPORT_SYMBOL(__kmalloc_node);
 #endif
 
+#ifdef CONFIG_HARDENED_USERCOPY
+/*
+ * Rejects objects that are incorrectly sized.
+ *
+ * Returns NULL if check passes, otherwise const char * to name of cache
+ * to indicate an error.
+ */
+const char *__check_heap_object(const void *ptr, unsigned long n,
+				struct page *page)
+{
+	struct kmem_cache *s;
+	unsigned long offset;
+	size_t object_size;
+
+	/* Find object and usable object size. */
+	s = page->slab_cache;
+	object_size = slab_ksize(s);
+
+	/* Reject impossible pointers. */
+	if (ptr < page_address(page))
+		return s->name;
+
+	/* Find offset within object. */
+	offset = (ptr - page_address(page)) % s->size;
+
+	/* Adjust for redzone and reject if within the redzone. */
+	if (kmem_cache_debug(s) && s->flags & SLAB_RED_ZONE) {
+		if (offset < s->red_left_pad)
+			return s->name;
+		offset -= s->red_left_pad;
+	}
+
+	/* Allow address range falling entirely within object size. */
+	if (offset <= object_size && n <= object_size - offset)
+		return NULL;
+
+	return s->name;
+}
+#endif /* CONFIG_HARDENED_USERCOPY */
+
 static size_t __ksize(const void *object)
 {
 	struct page *page;
diff --git a/mm/usercopy.c b/mm/usercopy.c
new file mode 100644
index 000000000000..f78015e8b1e5
--- /dev/null
+++ b/mm/usercopy.c
@@ -0,0 +1,269 @@
+/*
+ * This implements the various checks for CONFIG_HARDENED_USERCOPY*,
+ * which are designed to protect kernel memory from needless exposure
+ * and overwrite under many unintended conditions. This code is based
+ * on PAX_USERCOPY, which is:
+ *
+ * Copyright (C) 2001-2016 PaX Team, Bradley Spengler, Open Source
+ * Security Inc.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ *
+ */
+#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
+
+#include <linux/mm.h>
+#include <linux/sched.h>
+#include <linux/slab.h>
+#include <asm/sections.h>
+
+enum {
+	BAD_STACK = -1,
+	NOT_STACK = 0,
+	GOOD_FRAME,
+	GOOD_STACK,
+};
+
+/*
+ * Checks if a given pointer and length is contained by the current
+ * stack frame (if possible).
+ *
+ * Returns:
+ *	NOT_STACK: not at all on the stack
+ *	GOOD_FRAME: fully within a valid stack frame
+ *	GOOD_STACK: fully on the stack (when can't do frame-checking)
+ *	BAD_STACK: error condition (invalid stack position or bad stack frame)
+ */
+static noinline int check_stack_object(const void *obj, unsigned long len)
+{
+	const void * const stack = task_stack_page(current);
+	const void * const stackend = stack + THREAD_SIZE;
+	int ret;
+
+	/* Object is not on the stack at all. */
+	if (obj + len <= stack || stackend <= obj)
+		return NOT_STACK;
+
+	/*
+	 * Reject: object partially overlaps the stack (passing the
+	 * the check above means at least one end is within the stack,
+	 * so if this check fails, the other end is outside the stack).
+	 */
+	if (obj < stack || stackend < obj + len)
+		return BAD_STACK;
+
+	/* Check if object is safely within a valid frame. */
+	ret = arch_within_stack_frames(stack, stackend, obj, len);
+	if (ret)
+		return ret;
+
+	return GOOD_STACK;
+}
+
+static void report_usercopy(const void *ptr, unsigned long len,
+			    bool to_user, const char *type)
+{
+	pr_emerg("kernel memory %s attempt detected %s %p (%s) (%lu bytes)\n",
+		to_user ? "exposure" : "overwrite",
+		to_user ? "from" : "to", ptr, type ? : "unknown", len);
+	/*
+	 * For greater effect, it would be nice to do do_group_exit(),
+	 * but BUG() actually hooks all the lock-breaking and per-arch
+	 * Oops code, so that is used here instead.
+	 */
+	BUG();
+}
+
+/* Returns true if any portion of [ptr,ptr+n) over laps with [low,high). */
+static bool overlaps(const void *ptr, unsigned long n, unsigned long low,
+		     unsigned long high)
+{
+	unsigned long check_low = (uintptr_t)ptr;
+	unsigned long check_high = check_low + n;
+
+	/* Does not overlap if entirely above or entirely below. */
+	if (check_low >= high || check_high <= low)
+		return false;
+
+	return true;
+}
+
+/* Is this address range in the kernel text area? */
+static inline const char *check_kernel_text_object(const void *ptr,
+						   unsigned long n)
+{
+	unsigned long textlow = (unsigned long)_stext;
+	unsigned long texthigh = (unsigned long)_etext;
+	unsigned long textlow_linear, texthigh_linear;
+
+	if (overlaps(ptr, n, textlow, texthigh))
+		return "<kernel text>";
+
+	/*
+	 * Some architectures have virtual memory mappings with a secondary
+	 * mapping of the kernel text, i.e. there is more than one virtual
+	 * kernel address that points to the kernel image. It is usually
+	 * when there is a separate linear physical memory mapping, in that
+	 * __pa() is not just the reverse of __va(). This can be detected
+	 * and checked:
+	 */
+	textlow_linear = (unsigned long)__va(__pa(textlow));
+	/* No different mapping: we're done. */
+	if (textlow_linear == textlow)
+		return NULL;
+
+	/* Check the secondary mapping... */
+	texthigh_linear = (unsigned long)__va(__pa(texthigh));
+	if (overlaps(ptr, n, textlow_linear, texthigh_linear))
+		return "<linear kernel text>";
+
+	return NULL;
+}
+
+static inline const char *check_bogus_address(const void *ptr, unsigned long n)
+{
+	/* Reject if object wraps past end of memory. */
+	if ((unsigned long)ptr + n < (unsigned long)ptr)
+		return "<wrapped address>";
+
+	/* Reject if NULL or ZERO-allocation. */
+	if (ZERO_OR_NULL_PTR(ptr))
+		return "<null>";
+
+	return NULL;
+}
+
+static inline const char *check_heap_object(const void *ptr, unsigned long n,
+					    bool to_user)
+{
+	struct page *page, *endpage;
+	const void *end = ptr + n - 1;
+	bool is_reserved, is_cma;
+
+	/*
+	 * Some architectures (arm64) return true for virt_addr_valid() on
+	 * vmalloced addresses. Work around this by checking for vmalloc
+	 * first.
+	 */
+	if (is_vmalloc_addr(ptr))
+		return NULL;
+
+	if (!virt_addr_valid(ptr))
+		return NULL;
+
+	page = virt_to_head_page(ptr);
+
+	/* Check slab allocator for flags and size. */
+	if (PageSlab(page))
+		return __check_heap_object(ptr, n, page);
+
+	/*
+	 * Sometimes the kernel data regions are not marked Reserved (see
+	 * check below). And sometimes [_sdata,_edata) does not cover
+	 * rodata and/or bss, so check each range explicitly.
+	 */
+
+	/* Allow reads of kernel rodata region (if not marked as Reserved). */
+	if (ptr >= (const void *)__start_rodata &&
+	    end <= (const void *)__end_rodata) {
+		if (!to_user)
+			return "<rodata>";
+		return NULL;
+	}
+
+	/* Allow kernel data region (if not marked as Reserved). */
+	if (ptr >= (const void *)_sdata && end <= (const void *)_edata)
+		return NULL;
+
+	/* Allow kernel bss region (if not marked as Reserved). */
+	if (ptr >= (const void *)__bss_start &&
+	    end <= (const void *)__bss_stop)
+		return NULL;
+
+	/* Is the object wholly within one base page? */
+	if (likely(((unsigned long)ptr & (unsigned long)PAGE_MASK) ==
+		   ((unsigned long)end & (unsigned long)PAGE_MASK)))
+		return NULL;
+
+	/* Allow if start and end are inside the same compound page. */
+	endpage = virt_to_head_page(end);
+	if (likely(endpage == page))
+		return NULL;
+
+	/*
+	 * Reject if range is entirely either Reserved (i.e. special or
+	 * device memory), or CMA. Otherwise, reject since the object spans
+	 * several independently allocated pages.
+	 */
+	is_reserved = PageReserved(page);
+	is_cma = is_migrate_cma_page(page);
+	if (!is_reserved && !is_cma)
+		goto reject;
+
+	for (ptr += PAGE_SIZE; ptr <= end; ptr += PAGE_SIZE) {
+		page = virt_to_head_page(ptr);
+		if (is_reserved && !PageReserved(page))
+			goto reject;
+		if (is_cma && !is_migrate_cma_page(page))
+			goto reject;
+	}
+
+	return NULL;
+
+reject:
+	return "<spans multiple pages>";
+}
+
+/*
+ * Validates that the given object is:
+ * - not bogus address
+ * - known-safe heap or stack object
+ * - not in kernel text
+ */
+void __check_object_size(const void *ptr, unsigned long n, bool to_user)
+{
+	const char *err;
+
+	/* Skip all tests if size is zero. */
+	if (!n)
+		return;
+
+	/* Check for invalid addresses. */
+	err = check_bogus_address(ptr, n);
+	if (err)
+		goto report;
+
+	/* Check for bad heap object. */
+	err = check_heap_object(ptr, n, to_user);
+	if (err)
+		goto report;
+
+	/* Check for bad stack object. */
+	switch (check_stack_object(ptr, n)) {
+	case NOT_STACK:
+		/* Object is not touching the current process stack. */
+		break;
+	case GOOD_FRAME:
+	case GOOD_STACK:
+		/*
+		 * Object is either in the correct frame (when it
+		 * is possible to check) or just generally on the
+		 * process stack (when frame checking not available).
+		 */
+		return;
+	default:
+		err = "<process stack>";
+		goto report;
+	}
+
+	/* Check for object in kernel to avoid text exposure. */
+	err = check_kernel_text_object(ptr, n);
+	if (!err)
+		return;
+
+report:
+	report_usercopy(ptr, n, to_user, err);
+}
+EXPORT_SYMBOL(__check_object_size);