CRED: Wrap task credential accesses in the capabilities code

Wrap access to task credentials so that they can be separated more easily from
the task_struct during the introduction of COW creds.

Change most current->(|e|s|fs)[ug]id to current_(|e|s|fs)[ug]id().

Change some task->e?[ug]id to task_e?[ug]id().  In some places it makes more
sense to use RCU directly rather than a convenient wrapper; these will be
addressed by later patches.

Signed-off-by: David Howells <dhowells@redhat.com>
Reviewed-by: James Morris <jmorris@namei.org>
Acked-by: Serge Hallyn <serue@us.ibm.com>
Cc: Andrew G. Morgan <morgan@kernel.org>
Signed-off-by: James Morris <jmorris@namei.org>

1 files changed, 18 insertions, 12 deletions

diff --git a/security/commoncap.c b/security/commoncap.c
index dc06c0086b55..8283271f0768 100644
--- a/security/commoncap.c
+++ b/security/commoncap.c
@@ -362,7 +362,7 @@ int cap_bprm_set_security (struct linux_binprm *bprm)
                  * If only the real uid is 0, we do not set the effective
                  * bit.
                  */
-                if (bprm->e_uid == 0 || current->uid == 0) {
+                if (bprm->e_uid == 0 || current_uid() == 0) {
                         /* pP' = (cap_bset & ~0) | (pI & ~0) */
                         bprm->cap_post_exec_permitted = cap_combine(
                                 current->cap_bset, current->cap_inheritable
@@ -379,8 +379,12 @@ void cap_bprm_apply_creds (struct linux_binprm *bprm, int unsafe)
 {
         kernel_cap_t pP = current->cap_permitted;
         kernel_cap_t pE = current->cap_effective;
+        uid_t uid;
+        gid_t gid;
 
-        if (bprm->e_uid != current->uid || bprm->e_gid != current->gid ||
+        current_uid_gid(&uid, &gid);
+
+        if (bprm->e_uid != uid || bprm->e_gid != gid ||
             !cap_issubset(bprm->cap_post_exec_permitted,
                           current->cap_permitted)) {
                 set_dumpable(current->mm, suid_dumpable);
@@ -388,8 +392,8 @@ void cap_bprm_apply_creds (struct linux_binprm *bprm, int unsafe)
 
                 if (unsafe & ~LSM_UNSAFE_PTRACE_CAP) {
                         if (!capable(CAP_SETUID)) {
-                                bprm->e_uid = current->uid;
-                                bprm->e_gid = current->gid;
+                                bprm->e_uid = uid;
+                                bprm->e_gid = gid;
                         }
                         if (cap_limit_ptraced_target()) {
                                 bprm->cap_post_exec_permitted = cap_intersect(
@@ -437,15 +441,15 @@ void cap_bprm_apply_creds (struct linux_binprm *bprm, int unsafe)
 
 int cap_bprm_secureexec (struct linux_binprm *bprm)
 {
-        if (current->uid != 0) {
+        if (current_uid() != 0) {
                 if (bprm->cap_effective)
                         return 1;
                 if (!cap_isclear(bprm->cap_post_exec_permitted))
                         return 1;
         }
 
-        return (current->euid != current->uid ||
-                current->egid != current->gid);
+        return (current_euid() != current_uid() ||
+                current_egid() != current_gid());
 }
 
 int cap_inode_setxattr(struct dentry *dentry, const char *name,
@@ -508,16 +512,18 @@ int cap_inode_removexattr(struct dentry *dentry, const char *name)
 static inline void cap_emulate_setxuid (int old_ruid, int old_euid,
                                         int old_suid)
 {
+        uid_t euid = current_euid();
+
         if ((old_ruid == 0 || old_euid == 0 || old_suid == 0) &&
-            (current->uid != 0 && current->euid != 0 && current->suid != 0) &&
+            (current_uid()  != 0 && euid != 0 && current_suid() != 0) &&
             !issecure(SECURE_KEEP_CAPS)) {
                 cap_clear (current->cap_permitted);
                 cap_clear (current->cap_effective);
         }
-        if (old_euid == 0 && current->euid != 0) {
+        if (old_euid == 0 && euid != 0) {
                 cap_clear (current->cap_effective);
         }
-        if (old_euid != 0 && current->euid == 0) {
+        if (old_euid != 0 && euid == 0) {
                 current->cap_effective = current->cap_permitted;
         }
 }
@@ -546,12 +552,12 @@ int cap_task_post_setuid (uid_t old_ruid, uid_t old_euid, uid_t old_suid,
                          */
 
                         if (!issecure (SECURE_NO_SETUID_FIXUP)) {
-                                if (old_fsuid == 0 && current->fsuid != 0) {
+                                if (old_fsuid == 0 && current_fsuid() != 0) {
                                         current->cap_effective =
                                                 cap_drop_fs_set(
                                                     current->cap_effective);
                                 }
-                                if (old_fsuid != 0 && current->fsuid == 0) {
+                                if (old_fsuid != 0 && current_fsuid() == 0) {
                                         current->cap_effective =
                                                 cap_raise_fs_set(
                                                     current->cap_effective,