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selinux: Android kernel compatibility with M userspace

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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>
This commit is contained in:
Jeff Vander Stoep 2015-10-22 09:30:40 -07:00 committed by Zhao Wei Liew
parent 1e0918b3e9
commit cff5f5bf9b
1 changed files with 61 additions and 8 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

69
security/selinux/ss/avtab.c
View file

@ -335,6 +335,32 @@ void avtab_hash_eval(struct avtab *h, char *tag)
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 @@ int avtab_read_item(struct avtab *a, void *fp, struct policydb *pol,
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 @@ int avtab_read_item(struct avtab *a, void *fp, struct policydb *pol,
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 @@ int avtab_read_item(struct avtab *a, void *fp, struct policydb *pol,
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 @@ int avtab_write_item(struct policydb *p, struct avtab_node *cur, void *fp)
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;