12 files changed, 141 insertions, 60 deletions

diff --git a/include/linux/capability.h b/include/linux/capability.h
index 7d50ff6d269f..eaab759b1460 100644
--- a/include/linux/capability.h
+++ b/include/linux/capability.h
@@ -155,6 +155,7 @@ typedef struct kernel_cap_struct {
  *   Add any capability from current's capability bounding set
  *       to the current process' inheritable set
  *   Allow taking bits out of capability bounding set
+ *   Allow modification of the securebits for a process
  */
 
 #define CAP_SETPCAP          8
@@ -490,8 +491,6 @@ extern const kernel_cap_t __cap_init_eff_set;
 int capable(int cap);
 int __capable(struct task_struct *t, int cap);
 
-extern long cap_prctl_drop(unsigned long cap);
-
 #endif /* __KERNEL__ */
 
 #endif /* !_LINUX_CAPABILITY_H */
diff --git a/include/linux/init_task.h b/include/linux/init_task.h
index 37a6f5bc4a92..bf6b8a61f8db 100644
--- a/include/linux/init_task.h
+++ b/include/linux/init_task.h
@@ -9,6 +9,7 @@
 #include <linux/ipc.h>
 #include <linux/pid_namespace.h>
 #include <linux/user_namespace.h>
+#include <linux/securebits.h>
 #include <net/net_namespace.h>
 
 #define INIT_FDTABLE \
@@ -172,7 +173,7 @@ extern struct group_info init_groups;
         .cap_inheritable = CAP_INIT_INH_SET,                            \
         .cap_permitted  = CAP_FULL_SET,                                 \
         .cap_bset       = CAP_INIT_BSET,                                \
-        .keep_capabilities = 0,                                         \
+        .securebits     = SECUREBITS_DEFAULT,                           \
         .user           = INIT_USER,                                    \
         .comm           = "swapper",                                    \
         .thread         = INIT_THREAD,                                  \
diff --git a/include/linux/prctl.h b/include/linux/prctl.h
index 5c80b1939636..5ad79198d6f9 100644
--- a/include/linux/prctl.h
+++ b/include/linux/prctl.h
@@ -16,7 +16,8 @@
 # define PR_UNALIGN_NOPRINT     1       /* silently fix up unaligned user accesses */
 # define PR_UNALIGN_SIGBUS      2       /* generate SIGBUS on unaligned user access */
 
-/* Get/set whether or not to drop capabilities on setuid() away from uid 0 */
+/* Get/set whether or not to drop capabilities on setuid() away from
+ * uid 0 (as per security/commoncap.c) */
 #define PR_GET_KEEPCAPS   7
 #define PR_SET_KEEPCAPS   8
 
@@ -63,7 +64,7 @@
 #define PR_GET_SECCOMP  21
 #define PR_SET_SECCOMP  22
 
-/* Get/set the capability bounding set */
+/* Get/set the capability bounding set (as per security/commoncap.c) */
 #define PR_CAPBSET_READ 23
 #define PR_CAPBSET_DROP 24
 
@@ -73,4 +74,8 @@
 # define PR_TSC_ENABLE          1       /* allow the use of the timestamp counter */
 # define PR_TSC_SIGSEGV         2       /* throw a SIGSEGV instead of reading the TSC */
 
+/* Get/set securebits (as per security/commoncap.c) */
+#define PR_GET_SECUREBITS 27
+#define PR_SET_SECUREBITS 28
+
 #endif /* _LINUX_PRCTL_H */
diff --git a/include/linux/sched.h b/include/linux/sched.h
index 9a4f3e63e3bf..024d72b47a0c 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -68,7 +68,6 @@ struct sched_param {
 #include <linux/smp.h>
 #include <linux/sem.h>
 #include <linux/signal.h>
-#include <linux/securebits.h>
 #include <linux/fs_struct.h>
 #include <linux/compiler.h>
 #include <linux/completion.h>
@@ -1133,7 +1132,7 @@ struct task_struct {
         gid_t gid,egid,sgid,fsgid;
         struct group_info *group_info;
         kernel_cap_t   cap_effective, cap_inheritable, cap_permitted, cap_bset;
-        unsigned keep_capabilities:1;
+        unsigned securebits;
         struct user_struct *user;
 #ifdef CONFIG_KEYS
         struct key *request_key_auth;   /* assumed request_key authority */
diff --git a/include/linux/securebits.h b/include/linux/securebits.h
index 5b0617840fa4..c1f19dbceb05 100644
--- a/include/linux/securebits.h
+++ b/include/linux/securebits.h
@@ -3,28 +3,39 @@
 
 #define SECUREBITS_DEFAULT 0x00000000
 
-extern unsigned securebits;
-
 /* When set UID 0 has no special privileges. When unset, we support
    inheritance of root-permissions and suid-root executable under
    compatibility mode. We raise the effective and inheritable bitmasks
    *of the executable file* if the effective uid of the new process is
    0. If the real uid is 0, we raise the inheritable bitmask of the
    executable file. */
-#define SECURE_NOROOT            0
+#define SECURE_NOROOT                   0
+#define SECURE_NOROOT_LOCKED            1  /* make bit-0 immutable */
 
 /* When set, setuid to/from uid 0 does not trigger capability-"fixes"
    to be compatible with old programs relying on set*uid to loose
    privileges. When unset, setuid doesn't change privileges. */
-#define SECURE_NO_SETUID_FIXUP   2
+#define SECURE_NO_SETUID_FIXUP          2
+#define SECURE_NO_SETUID_FIXUP_LOCKED   3  /* make bit-2 immutable */
+
+/* When set, a process can retain its capabilities even after
+   transitioning to a non-root user (the set-uid fixup suppressed by
+   bit 2). Bit-4 is cleared when a process calls exec(); setting both
+   bit 4 and 5 will create a barrier through exec that no exec()'d
+   child can use this feature again. */
+#define SECURE_KEEP_CAPS                4
+#define SECURE_KEEP_CAPS_LOCKED         5  /* make bit-4 immutable */
 
 /* Each securesetting is implemented using two bits. One bit specify
    whether the setting is on or off. The other bit specify whether the
    setting is fixed or not. A setting which is fixed cannot be changed
    from user-level. */
+#define issecure_mask(X)        (1 << (X))
+#define issecure(X)             (issecure_mask(X) & current->securebits)
 
-#define issecure(X) ( (1 << (X+1)) & SECUREBITS_DEFAULT ?       \
-                      (1 << (X)) & SECUREBITS_DEFAULT :         \
-                      (1 << (X)) & securebits )
+#define SECURE_ALL_BITS         (issecure_mask(SECURE_NOROOT) | \
+                                 issecure_mask(SECURE_NO_SETUID_FIXUP) | \
+                                 issecure_mask(SECURE_KEEP_CAPS))
+#define SECURE_ALL_LOCKS        (SECURE_ALL_BITS << 1)
 
 #endif /* !_LINUX_SECUREBITS_H */
diff --git a/include/linux/security.h b/include/linux/security.h
index 53a34539382a..e6299e50e210 100644
--- a/include/linux/security.h
+++ b/include/linux/security.h
@@ -34,8 +34,6 @@
 #include <linux/xfrm.h>
 #include <net/flow.h>
 
-extern unsigned securebits;
-
 /* Maximum number of letters for an LSM name string */
 #define SECURITY_NAME_MAX       10
 
@@ -61,6 +59,8 @@ extern int cap_inode_need_killpriv(struct dentry *dentry);
 extern int cap_inode_killpriv(struct dentry *dentry);
 extern int cap_task_post_setuid (uid_t old_ruid, uid_t old_euid, uid_t old_suid, int flags);
 extern void cap_task_reparent_to_init (struct task_struct *p);
+extern int cap_task_prctl(int option, unsigned long arg2, unsigned long arg3,
+                          unsigned long arg4, unsigned long arg5, long *rc_p);
 extern int cap_task_setscheduler (struct task_struct *p, int policy, struct sched_param *lp);
 extern int cap_task_setioprio (struct task_struct *p, int ioprio);
 extern int cap_task_setnice (struct task_struct *p, int nice);
@@ -720,7 +720,9 @@ static inline void security_free_mnt_opts(struct security_mnt_opts *opts)
  *      @arg3 contains a argument.
  *      @arg4 contains a argument.
  *      @arg5 contains a argument.
- *      Return 0 if permission is granted.
+ *      @rc_p contains a pointer to communicate back the forced return code
+ *      Return 0 if permission is granted, and non-zero if the security module
+ *      has taken responsibility (setting *rc_p) for the prctl call.
  * @task_reparent_to_init:
  *      Set the security attributes in @p->security for a kernel thread that
  *      is being reparented to the init task.
@@ -1420,7 +1422,7 @@ struct security_operations {
         int (*task_wait) (struct task_struct * p);
         int (*task_prctl) (int option, unsigned long arg2,
                            unsigned long arg3, unsigned long arg4,
-                           unsigned long arg5);
+                           unsigned long arg5, long *rc_p);
         void (*task_reparent_to_init) (struct task_struct * p);
         void (*task_to_inode)(struct task_struct *p, struct inode *inode);
 
@@ -1684,7 +1686,7 @@ int security_task_kill(struct task_struct *p, struct siginfo *info,
                         int sig, u32 secid);
 int security_task_wait(struct task_struct *p);
 int security_task_prctl(int option, unsigned long arg2, unsigned long arg3,
-                         unsigned long arg4, unsigned long arg5);
+                         unsigned long arg4, unsigned long arg5, long *rc_p);
 void security_task_reparent_to_init(struct task_struct *p);
 void security_task_to_inode(struct task_struct *p, struct inode *inode);
 int security_ipc_permission(struct kern_ipc_perm *ipcp, short flag);
@@ -2271,9 +2273,9 @@ static inline int security_task_wait (struct task_struct *p)
 static inline int security_task_prctl (int option, unsigned long arg2,
                                        unsigned long arg3,
                                        unsigned long arg4,
-                                       unsigned long arg5)
+                                       unsigned long arg5, long *rc_p)
 {
-        return 0;
+        return cap_task_prctl(option, arg2, arg3, arg3, arg5, rc_p);
 }
 
 static inline void security_task_reparent_to_init (struct task_struct *p)
diff --git a/kernel/sys.c b/kernel/sys.c
index 6a0cc71ee88d..f2a451366953 100644
--- a/kernel/sys.c
+++ b/kernel/sys.c
@@ -1632,10 +1632,9 @@ asmlinkage long sys_umask(int mask)
 asmlinkage long sys_prctl(int option, unsigned long arg2, unsigned long arg3,
                           unsigned long arg4, unsigned long arg5)
 {
-        long error;
+        long uninitialized_var(error);
 
-        error = security_task_prctl(option, arg2, arg3, arg4, arg5);
-        if (error)
+        if (security_task_prctl(option, arg2, arg3, arg4, arg5, &error))
                 return error;
 
         switch (option) {
@@ -1688,17 +1687,6 @@ asmlinkage long sys_prctl(int option, unsigned long arg2, unsigned long arg3,
                                 error = -EINVAL;
                         break;
 
-                case PR_GET_KEEPCAPS:
-                        if (current->keep_capabilities)
-                                error = 1;
-                        break;
-                case PR_SET_KEEPCAPS:
-                        if (arg2 != 0 && arg2 != 1) {
-                                error = -EINVAL;
-                                break;
-                        }
-                        current->keep_capabilities = arg2;
-                        break;
                 case PR_SET_NAME: {
                         struct task_struct *me = current;
                         unsigned char ncomm[sizeof(me->comm)];
@@ -1732,17 +1720,6 @@ asmlinkage long sys_prctl(int option, unsigned long arg2, unsigned long arg3,
                 case PR_SET_SECCOMP:
                         error = prctl_set_seccomp(arg2);
                         break;
-
-                case PR_CAPBSET_READ:
-                        if (!cap_valid(arg2))
-                                return -EINVAL;
-                        return !!cap_raised(current->cap_bset, arg2);
-                case PR_CAPBSET_DROP:
-#ifdef CONFIG_SECURITY_FILE_CAPABILITIES
-                        return cap_prctl_drop(arg2);
-#else
-                        return -EINVAL;
-#endif
                 case PR_GET_TSC:
                         error = GET_TSC_CTL(arg2);
                         break;
diff --git a/security/capability.c b/security/capability.c
index 2c6e06d18fab..38ac54e3aed1 100644
--- a/security/capability.c
+++ b/security/capability.c
@@ -44,6 +44,7 @@ static struct security_operations capability_ops = {
         .task_setioprio =               cap_task_setioprio,
         .task_setnice =                 cap_task_setnice,
         .task_post_setuid =             cap_task_post_setuid,
+        .task_prctl =                   cap_task_prctl,
         .task_reparent_to_init =        cap_task_reparent_to_init,
 
         .syslog =                       cap_syslog,
diff --git a/security/commoncap.c b/security/commoncap.c
index 852905789caf..e8c3f5e46705 100644
--- a/security/commoncap.c
+++ b/security/commoncap.c
@@ -24,11 +24,8 @@
 #include <linux/hugetlb.h>
 #include <linux/mount.h>
 #include <linux/sched.h>
-
-/* Global security state */
-
-unsigned securebits = SECUREBITS_DEFAULT; /* systemwide security settings */
-EXPORT_SYMBOL(securebits);
+#include <linux/prctl.h>
+#include <linux/securebits.h>
 
 int cap_netlink_send(struct sock *sk, struct sk_buff *skb)
 {
@@ -368,7 +365,7 @@ void cap_bprm_apply_creds (struct linux_binprm *bprm, int unsafe)
 
         /* AUD: Audit candidate if current->cap_effective is set */
 
-        current->keep_capabilities = 0;
+        current->securebits &= ~issecure_mask(SECURE_KEEP_CAPS);
 }
 
 int cap_bprm_secureexec (struct linux_binprm *bprm)
@@ -448,7 +445,7 @@ static inline void cap_emulate_setxuid (int old_ruid, int old_euid,
 {
         if ((old_ruid == 0 || old_euid == 0 || old_suid == 0) &&
             (current->uid != 0 && current->euid != 0 && current->suid != 0) &&
-            !current->keep_capabilities) {
+            !issecure(SECURE_KEEP_CAPS)) {
                 cap_clear (current->cap_permitted);
                 cap_clear (current->cap_effective);
         }
@@ -547,7 +544,7 @@ int cap_task_setnice (struct task_struct *p, int nice)
  * this task could get inconsistent info.  There can be no
  * racing writer bc a task can only change its own caps.
  */
-long cap_prctl_drop(unsigned long cap)
+static long cap_prctl_drop(unsigned long cap)
 {
         if (!capable(CAP_SETPCAP))
                 return -EPERM;
@@ -556,6 +553,7 @@ long cap_prctl_drop(unsigned long cap)
         cap_lower(current->cap_bset, cap);
         return 0;
 }
+
 #else
 int cap_task_setscheduler (struct task_struct *p, int policy,
                            struct sched_param *lp)
@@ -572,12 +570,99 @@ int cap_task_setnice (struct task_struct *p, int nice)
 }
 #endif
 
+int cap_task_prctl(int option, unsigned long arg2, unsigned long arg3,
+                   unsigned long arg4, unsigned long arg5, long *rc_p)
+{
+        long error = 0;
+
+        switch (option) {
+        case PR_CAPBSET_READ:
+                if (!cap_valid(arg2))
+                        error = -EINVAL;
+                else
+                        error = !!cap_raised(current->cap_bset, arg2);
+                break;
+#ifdef CONFIG_SECURITY_FILE_CAPABILITIES
+        case PR_CAPBSET_DROP:
+                error = cap_prctl_drop(arg2);
+                break;
+
+        /*
+         * The next four prctl's remain to assist with transitioning a
+         * system from legacy UID=0 based privilege (when filesystem
+         * capabilities are not in use) to a system using filesystem
+         * capabilities only - as the POSIX.1e draft intended.
+         *
+         * Note:
+         *
+         *  PR_SET_SECUREBITS =
+         *      issecure_mask(SECURE_KEEP_CAPS_LOCKED)
+         *    | issecure_mask(SECURE_NOROOT)
+         *    | issecure_mask(SECURE_NOROOT_LOCKED)
+         *    | issecure_mask(SECURE_NO_SETUID_FIXUP)
+         *    | issecure_mask(SECURE_NO_SETUID_FIXUP_LOCKED)
+         *
+         * will ensure that the current process and all of its
+         * children will be locked into a pure
+         * capability-based-privilege environment.
+         */
+        case PR_SET_SECUREBITS:
+                if ((((current->securebits & SECURE_ALL_LOCKS) >> 1)
+                     & (current->securebits ^ arg2))                  /*[1]*/
+                    || ((current->securebits & SECURE_ALL_LOCKS
+                         & ~arg2))                                    /*[2]*/
+                    || (arg2 & ~(SECURE_ALL_LOCKS | SECURE_ALL_BITS)) /*[3]*/
+                    || (cap_capable(current, CAP_SETPCAP) != 0)) {    /*[4]*/
+                        /*
+                         * [1] no changing of bits that are locked
+                         * [2] no unlocking of locks
+                         * [3] no setting of unsupported bits
+                         * [4] doing anything requires privilege (go read about
+                         *     the "sendmail capabilities bug")
+                         */
+                        error = -EPERM;  /* cannot change a locked bit */
+                } else {
+                        current->securebits = arg2;
+                }
+                break;
+        case PR_GET_SECUREBITS:
+                error = current->securebits;
+                break;
+
+#endif /* def CONFIG_SECURITY_FILE_CAPABILITIES */
+
+        case PR_GET_KEEPCAPS:
+                if (issecure(SECURE_KEEP_CAPS))
+                        error = 1;
+                break;
+        case PR_SET_KEEPCAPS:
+                if (arg2 > 1) /* Note, we rely on arg2 being unsigned here */
+                        error = -EINVAL;
+                else if (issecure(SECURE_KEEP_CAPS_LOCKED))
+                        error = -EPERM;
+                else if (arg2)
+                        current->securebits |= issecure_mask(SECURE_KEEP_CAPS);
+                else
+                        current->securebits &=
+                                ~issecure_mask(SECURE_KEEP_CAPS);
+                break;
+
+        default:
+                /* No functionality available - continue with default */
+                return 0;
+        }
+
+        /* Functionality provided */
+        *rc_p = error;
+        return 1;
+}
+
 void cap_task_reparent_to_init (struct task_struct *p)
 {
         cap_set_init_eff(p->cap_effective);
         cap_clear(p->cap_inheritable);
         cap_set_full(p->cap_permitted);
-        p->keep_capabilities = 0;
+        p->securebits = SECUREBITS_DEFAULT;
         return;
 }
 
diff --git a/security/dummy.c b/security/dummy.c
index b0232bbf427b..58d4dd1af5c7 100644
--- a/security/dummy.c
+++ b/security/dummy.c
@@ -604,7 +604,7 @@ static int dummy_task_kill (struct task_struct *p, struct siginfo *info,
 }
 
 static int dummy_task_prctl (int option, unsigned long arg2, unsigned long arg3,
-                             unsigned long arg4, unsigned long arg5)
+                             unsigned long arg4, unsigned long arg5, long *rc_p)
 {
         return 0;
 }
diff --git a/security/security.c b/security/security.c
index 8a285c7b9962..d5cb5898d967 100644
--- a/security/security.c
+++ b/security/security.c
@@ -733,9 +733,9 @@ int security_task_wait(struct task_struct *p)
 }
 
 int security_task_prctl(int option, unsigned long arg2, unsigned long arg3,
-                         unsigned long arg4, unsigned long arg5)
+                         unsigned long arg4, unsigned long arg5, long *rc_p)
 {
-        return security_ops->task_prctl(option, arg2, arg3, arg4, arg5);
+        return security_ops->task_prctl(option, arg2, arg3, arg4, arg5, rc_p);
 }
 
 void security_task_reparent_to_init(struct task_struct *p)
diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c
index 308e2cf17d75..04acb5af8317 100644
--- a/security/selinux/hooks.c
+++ b/security/selinux/hooks.c
@@ -3303,12 +3303,13 @@ static int selinux_task_prctl(int option,
                               unsigned long arg2,
                               unsigned long arg3,
                               unsigned long arg4,
-                              unsigned long arg5)
+                              unsigned long arg5,
+                              long *rc_p)
 {
         /* The current prctl operations do not appear to require
            any SELinux controls since they merely observe or modify
            the state of the current process. */
-        return 0;
+        return secondary_ops->task_prctl(option, arg2, arg3, arg4, arg5, rc_p);
 }
 
 static int selinux_task_wait(struct task_struct *p)