selinux: Android kernel compatibility with M userspace
NOT intended for new Android devices - this commit is unnecessary
for a target device that does not have a previous M variant.
DO NOT upstream. Android only.
Motivation:
This commit mitigates a mismatch between selinux kernel and
selinux userspace. The selinux ioctl white-listing binary policy
format that was accepted into Android M differs slightly from what
was later accepted into the upstream kernel. This leaves Android
master branch kernels incompatible with Android M releases. This
patch restores backwards compatibility. This is important because:
1. kernels may be updated on a different cycle than the rest of the
OS e.g. security patching.
2. Android M bringup may still be ongoing for some devices. The
same kernel should work for both M and master.
Backwards compatibility is achieved by checking for an Android M
policy characteristic during initial policy read and converting to
upstream policy format. The inverse conversion is done for policy
write as required for CTS testing.
Bug: 22846070
Change-Id: I2f1ee2eee402f37cf3c9df9f9e03c1b9ddec1929
Signed-off-by: Jeff Vander Stoep <jeffv@google.com>
diff --git a/security/selinux/ss/avtab.c b/security/selinux/ss/avtab.c
index a6bef63..640c16b 100644
--- a/security/selinux/ss/avtab.c
+++ b/security/selinux/ss/avtab.c
@@ -335,6 +335,32 @@
chain2_len_sum);
}
+/*
+ * extended permissions compatibility. Make ToT Android kernels compatible
+ * with Android M releases
+ */
+#define AVTAB_OPTYPE_ALLOWED 0x1000
+#define AVTAB_OPTYPE_AUDITALLOW 0x2000
+#define AVTAB_OPTYPE_DONTAUDIT 0x4000
+#define AVTAB_OPTYPE (AVTAB_OPTYPE_ALLOWED | \
+ AVTAB_OPTYPE_AUDITALLOW | \
+ AVTAB_OPTYPE_DONTAUDIT)
+#define AVTAB_XPERMS_OPTYPE 4
+
+#define avtab_xperms_to_optype(x) (x << AVTAB_XPERMS_OPTYPE)
+#define avtab_optype_to_xperms(x) (x >> AVTAB_XPERMS_OPTYPE)
+
+static unsigned int avtab_android_m_compat;
+
+static void avtab_android_m_compat_set(void)
+{
+ if (!avtab_android_m_compat) {
+ pr_info("SELinux: Android master kernel running Android"
+ " M policy in compatibility mode.\n");
+ avtab_android_m_compat = 1;
+ }
+}
+
static uint16_t spec_order[] = {
AVTAB_ALLOWED,
AVTAB_AUDITDENY,
@@ -359,6 +385,7 @@
struct avtab_datum datum;
struct avtab_extended_perms xperms;
__le32 buf32[ARRAY_SIZE(xperms.perms.p)];
+ unsigned int android_m_compat_optype = 0;
int i, rc;
unsigned set;
@@ -449,6 +476,13 @@
key.target_class = le16_to_cpu(buf16[items++]);
key.specified = le16_to_cpu(buf16[items++]);
+ if ((key.specified & AVTAB_OPTYPE) &&
+ (vers == POLICYDB_VERSION_XPERMS_IOCTL)) {
+ key.specified = avtab_optype_to_xperms(key.specified);
+ android_m_compat_optype = 1;
+ avtab_android_m_compat_set();
+ }
+
if (!policydb_type_isvalid(pol, key.source_type) ||
!policydb_type_isvalid(pol, key.target_type) ||
!policydb_class_isvalid(pol, key.target_class)) {
@@ -479,10 +513,22 @@
printk(KERN_ERR "SELinux: avtab: truncated entry\n");
return rc;
}
- rc = next_entry(&xperms.driver, fp, sizeof(u8));
- if (rc) {
- printk(KERN_ERR "SELinux: avtab: truncated entry\n");
- return rc;
+ if (avtab_android_m_compat ||
+ ((xperms.specified != AVTAB_XPERMS_IOCTLFUNCTION) &&
+ (xperms.specified != AVTAB_XPERMS_IOCTLDRIVER) &&
+ (vers == POLICYDB_VERSION_XPERMS_IOCTL))) {
+ xperms.driver = xperms.specified;
+ if (android_m_compat_optype)
+ xperms.specified = AVTAB_XPERMS_IOCTLDRIVER;
+ else
+ xperms.specified = AVTAB_XPERMS_IOCTLFUNCTION;
+ avtab_android_m_compat_set();
+ } else {
+ rc = next_entry(&xperms.driver, fp, sizeof(u8));
+ if (rc) {
+ printk(KERN_ERR "SELinux: avtab: truncated entry\n");
+ return rc;
+ }
}
rc = next_entry(buf32, fp, sizeof(u32)*ARRAY_SIZE(xperms.perms.p));
if (rc) {
@@ -568,15 +614,22 @@
buf16[0] = cpu_to_le16(cur->key.source_type);
buf16[1] = cpu_to_le16(cur->key.target_type);
buf16[2] = cpu_to_le16(cur->key.target_class);
- buf16[3] = cpu_to_le16(cur->key.specified);
+ if (avtab_android_m_compat && (cur->key.specified & AVTAB_XPERMS) &&
+ (cur->datum.u.xperms->specified == AVTAB_XPERMS_IOCTLDRIVER))
+ buf16[3] = cpu_to_le16(avtab_xperms_to_optype(cur->key.specified));
+ else
+ buf16[3] = cpu_to_le16(cur->key.specified);
rc = put_entry(buf16, sizeof(u16), 4, fp);
if (rc)
return rc;
if (cur->key.specified & AVTAB_XPERMS) {
- rc = put_entry(&cur->datum.u.xperms->specified, sizeof(u8), 1, fp);
- if (rc)
- return rc;
+ if (avtab_android_m_compat == 0) {
+ rc = put_entry(&cur->datum.u.xperms->specified,
+ sizeof(u8), 1, fp);
+ if (rc)
+ return rc;
+ }
rc = put_entry(&cur->datum.u.xperms->driver, sizeof(u8), 1, fp);
if (rc)
return rc;
