Merge tag 'usercopy-v4.16-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/kees/linux

Pull hardened usercopy whitelisting from Kees Cook:
 "Currently, hardened usercopy performs dynamic bounds checking on slab
  cache objects. This is good, but still leaves a lot of kernel memory
  available to be copied to/from userspace in the face of bugs.

  To further restrict what memory is available for copying, this creates
  a way to whitelist specific areas of a given slab cache object for
  copying to/from userspace, allowing much finer granularity of access
  control.

  Slab caches that are never exposed to userspace can declare no
  whitelist for their objects, thereby keeping them unavailable to
  userspace via dynamic copy operations. (Note, an implicit form of
  whitelisting is the use of constant sizes in usercopy operations and
  get_user()/put_user(); these bypass all hardened usercopy checks since
  these sizes cannot change at runtime.)

  This new check is WARN-by-default, so any mistakes can be found over
  the next several releases without breaking anyone's system.

  The series has roughly the following sections:
   - remove %p and improve reporting with offset
   - prepare infrastructure and whitelist kmalloc
   - update VFS subsystem with whitelists
   - update SCSI subsystem with whitelists
   - update network subsystem with whitelists
   - update process memory with whitelists
   - update per-architecture thread_struct with whitelists
   - update KVM with whitelists and fix ioctl bug
   - mark all other allocations as not whitelisted
   - update lkdtm for more sensible test overage"

* tag 'usercopy-v4.16-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/kees/linux: (38 commits)
  lkdtm: Update usercopy tests for whitelisting
  usercopy: Restrict non-usercopy caches to size 0
  kvm: x86: fix KVM_XEN_HVM_CONFIG ioctl
  kvm: whitelist struct kvm_vcpu_arch
  arm: Implement thread_struct whitelist for hardened usercopy
  arm64: Implement thread_struct whitelist for hardened usercopy
  x86: Implement thread_struct whitelist for hardened usercopy
  fork: Provide usercopy whitelisting for task_struct
  fork: Define usercopy region in thread_stack slab caches
  fork: Define usercopy region in mm_struct slab caches
  net: Restrict unwhitelisted proto caches to size 0
  sctp: Copy struct sctp_sock.autoclose to userspace using put_user()
  sctp: Define usercopy region in SCTP proto slab cache
  caif: Define usercopy region in caif proto slab cache
  ip: Define usercopy region in IP proto slab cache
  net: Define usercopy region in struct proto slab cache
  scsi: Define usercopy region in scsi_sense_cache slab cache
  cifs: Define usercopy region in cifs_request slab cache
  vxfs: Define usercopy region in vxfs_inode slab cache
  ufs: Define usercopy region in ufs_inode_cache slab cache
  ...

1 files changed, 37 insertions, 12 deletions

diff --git a/mm/slub.c b/mm/slub.c
index 693b707..cc71176 100644
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -3813,13 +3813,15 @@ EXPORT_SYMBOL(__kmalloc_node);
 
 #ifdef CONFIG_HARDENED_USERCOPY
 /*
- * Rejects objects that are incorrectly sized.
+ * Rejects incorrectly sized objects and objects that are to be copied
+ * to/from userspace but do not fall entirely within the containing slab
+ * cache's usercopy region.
  *
  * 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)
+void __check_heap_object(const void *ptr, unsigned long n, struct page *page,
+			 bool to_user)
 {
 	struct kmem_cache *s;
 	unsigned long offset;
@@ -3827,11 +3829,11 @@ const char *__check_heap_object(const void *ptr, unsigned long n,
 
 	/* 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;
+		usercopy_abort("SLUB object not in SLUB page?!", NULL,
+			       to_user, 0, n);
 
 	/* Find offset within object. */
 	offset = (ptr - page_address(page)) % s->size;
@@ -3839,15 +3841,31 @@ const char *__check_heap_object(const void *ptr, unsigned long n,
 	/* 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;
+			usercopy_abort("SLUB object in left red zone",
+				       s->name, to_user, offset, n);
 		offset -= s->red_left_pad;
 	}
 
-	/* Allow address range falling entirely within object size. */
-	if (offset <= object_size && n <= object_size - offset)
-		return NULL;
+	/* Allow address range falling entirely within usercopy region. */
+	if (offset >= s->useroffset &&
+	    offset - s->useroffset <= s->usersize &&
+	    n <= s->useroffset - offset + s->usersize)
+		return;
+
+	/*
+	 * If the copy is still within the allocated object, produce
+	 * a warning instead of rejecting the copy. This is intended
+	 * to be a temporary method to find any missing usercopy
+	 * whitelists.
+	 */
+	object_size = slab_ksize(s);
+	if (usercopy_fallback &&
+	    offset <= object_size && n <= object_size - offset) {
+		usercopy_warn("SLUB object", s->name, to_user, offset, n);
+		return;
+	}
 
-	return s->name;
+	usercopy_abort("SLUB object", s->name, to_user, offset, n);
 }
 #endif /* CONFIG_HARDENED_USERCOPY */
 
@@ -4181,7 +4199,7 @@ void __init kmem_cache_init(void)
 	kmem_cache = &boot_kmem_cache;
 
 	create_boot_cache(kmem_cache_node, "kmem_cache_node",
-		sizeof(struct kmem_cache_node), SLAB_HWCACHE_ALIGN);
+		sizeof(struct kmem_cache_node), SLAB_HWCACHE_ALIGN, 0, 0);
 
 	register_hotmemory_notifier(&slab_memory_callback_nb);
 
@@ -4191,7 +4209,7 @@ void __init kmem_cache_init(void)
 	create_boot_cache(kmem_cache, "kmem_cache",
 			offsetof(struct kmem_cache, node) +
 				nr_node_ids * sizeof(struct kmem_cache_node *),
-		       SLAB_HWCACHE_ALIGN);
+		       SLAB_HWCACHE_ALIGN, 0, 0);
 
 	kmem_cache = bootstrap(&boot_kmem_cache);
 
@@ -5061,6 +5079,12 @@ static ssize_t cache_dma_show(struct kmem_cache *s, char *buf)
 SLAB_ATTR_RO(cache_dma);
 #endif
 
+static ssize_t usersize_show(struct kmem_cache *s, char *buf)
+{
+	return sprintf(buf, "%zu\n", s->usersize);
+}
+SLAB_ATTR_RO(usersize);
+
 static ssize_t destroy_by_rcu_show(struct kmem_cache *s, char *buf)
 {
 	return sprintf(buf, "%d\n", !!(s->flags & SLAB_TYPESAFE_BY_RCU));
@@ -5435,6 +5459,7 @@ static struct attribute *slab_attrs[] = {
 #ifdef CONFIG_FAILSLAB
 	&failslab_attr.attr,
 #endif
+	&usersize_attr.attr,
 
 	NULL
 };