From 969f47d4b1986f2950ebfdba90012da60c2aab48 Mon Sep 17 00:00:00 2001 From: Jeff Vander Stoep Date: Thu, 22 Oct 2015 09:30:40 -0700 Subject: [PATCH] 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 --- security/selinux/ss/avtab.c | 69 ++++++++++++++++++++++++++++++++----- 1 file changed, 61 insertions(+), 8 deletions(-) diff --git a/security/selinux/ss/avtab.c b/security/selinux/ss/avtab.c index 3628d3a868b6..31345376aa9b 100644 --- a/security/selinux/ss/avtab.c +++ b/security/selinux/ss/avtab.c @@ -374,6 +374,32 @@ 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, @@ -398,6 +424,7 @@ 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; @@ -488,6 +515,13 @@ 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)) { @@ -518,10 +552,22 @@ 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) { @@ -607,15 +653,22 @@ 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; -- 2.20.1