1 files changed, 122 insertions, 53 deletions

diff --git a/security/commoncap.c b/security/commoncap.c
index 98ff4630f9f..aa5120e59b4 100644
--- a/security/commoncap.c
+++ b/security/commoncap.c
@@ -274,6 +274,16 @@ int cap_capset(struct cred *new,
 	new->cap_effective   = *effective;
 	new->cap_inheritable = *inheritable;
 	new->cap_permitted   = *permitted;
+
+	/*
+	 * Mask off ambient bits that are no longer both permitted and
+	 * inheritable.
+	 */
+	new->cap_ambient = cap_intersect(new->cap_ambient,
+					 cap_intersect(*permitted,
+						       *inheritable));
+	if (WARN_ON(!cap_ambient_invariant_ok(new)))
+		return -EINVAL;
 	return 0;
 }
 
@@ -354,6 +364,7 @@ static inline int bprm_caps_from_vfs_caps(struct cpu_vfs_cap_data *caps,
 
 		/*
 		 * pP' = (X & fP) | (pI & fI)
+		 * The addition of pA' is handled later.
 		 */
 		new->cap_permitted.cap[i] =
 			(new->cap_bset.cap[i] & permitted) |
@@ -482,9 +493,12 @@ int cap_bprm_set_creds(struct linux_binprm *bprm)
 {
 	const struct cred *old = current_cred();
 	struct cred *new = bprm->cred;
-	bool effective, has_cap = false;
+	bool effective, has_cap = false, is_setid;
 	int ret;
 
+	if (WARN_ON(!cap_ambient_invariant_ok(old)))
+		return -EPERM;
+
 	effective = false;
 	ret = get_file_caps(bprm, &effective, &has_cap);
 	if (ret < 0)
@@ -527,8 +541,9 @@ skip:
 	 *
 	 * In addition, if NO_NEW_PRIVS, then ensure we get no new privs.
 	 */
-	if ((new->euid != old->uid ||
-	     new->egid != old->gid ||
+	is_setid = new->euid != old->uid || new->egid != old->gid;
+
+	if ((is_setid ||
 	     !cap_issubset(new->cap_permitted, old->cap_permitted)) &&
 	    bprm->unsafe & ~LSM_UNSAFE_PTRACE_CAP) {
 		/* downgrade; they get no more than they had, and maybe less */
@@ -544,10 +559,28 @@ skip:
 	new->suid = new->fsuid = new->euid;
 	new->sgid = new->fsgid = new->egid;
 
+	/* File caps or setid cancels ambient. */
+	if (has_cap || is_setid)
+		cap_clear(new->cap_ambient);
+
+	/*
+	 * Now that we've computed pA', update pP' to give:
+	 *   pP' = (X & fP) | (pI & fI) | pA'
+	 */
+	new->cap_permitted = cap_combine(new->cap_permitted, new->cap_ambient);
+
+	/*
+	 * Set pE' = (fE ? pP' : pA').  Because pA' is zero if fE is set,
+	 * this is the same as pE' = (fE ? pP' : 0) | pA'.
+	 */
 	if (effective)
 		new->cap_effective = new->cap_permitted;
 	else
-		cap_clear(new->cap_effective);
+		new->cap_effective = new->cap_ambient;
+
+	if (WARN_ON(!cap_ambient_invariant_ok(new)))
+		return -EPERM;
+
 	bprm->cap_effective = effective;
 
 	/*
@@ -562,7 +595,7 @@ skip:
 	 * Number 1 above might fail if you don't have a full bset, but I think
 	 * that is interesting information to audit.
 	 */
-	if (!cap_isclear(new->cap_effective)) {
+	if (!cap_issubset(new->cap_effective, new->cap_ambient)) {
 		if (!cap_issubset(CAP_FULL_SET, new->cap_effective) ||
 		    new->euid != 0 || new->uid != 0 ||
 		    issecure(SECURE_NOROOT)) {
@@ -573,6 +606,10 @@ skip:
 	}
 
 	new->securebits &= ~issecure_mask(SECURE_KEEP_CAPS);
+
+	if (WARN_ON(!cap_ambient_invariant_ok(new)))
+		return -EPERM;
+
 	return 0;
 }
 
@@ -593,7 +630,7 @@ int cap_bprm_secureexec(struct linux_binprm *bprm)
 	if (cred->uid != 0) {
 		if (bprm->cap_effective)
 			return 1;
-		if (!cap_isclear(cred->cap_permitted))
+		if (!cap_issubset(cred->cap_permitted, cred->cap_ambient))
 			return 1;
 	}
 
@@ -689,10 +726,17 @@ int cap_inode_removexattr(struct dentry *dentry, const char *name)
 static inline void cap_emulate_setxuid(struct cred *new, const struct cred *old)
 {
 	if ((old->uid == 0 || old->euid == 0 || old->suid == 0) &&
-	    (new->uid != 0 && new->euid != 0 && new->suid != 0) &&
-	    !issecure(SECURE_KEEP_CAPS)) {
-		cap_clear(new->cap_permitted);
-		cap_clear(new->cap_effective);
+	    (new->uid != 0 && new->euid != 0 && new->suid != 0)) {
+		if (!issecure(SECURE_KEEP_CAPS)) {
+			cap_clear(new->cap_permitted);
+			cap_clear(new->cap_effective);
+		}
+		/*
+		 * Pre-ambient programs expect setresuid to nonroot followed
+		 * by exec to drop capabilities.  We should make sure that
+		 * this remains the case.
+		 */
+		cap_clear(new->cap_ambient);
 	}
 	if (old->euid == 0 && new->euid != 0)
 		cap_clear(new->cap_effective);
@@ -813,15 +857,20 @@ int cap_task_setnice(struct task_struct *p, int nice)
  * Implement PR_CAPBSET_DROP.  Attempt to remove the specified capability from
  * the current task's bounding set.  Returns 0 on success, -ve on error.
  */
-static long cap_prctl_drop(struct cred *new, unsigned long cap)
+static int cap_prctl_drop(unsigned long cap)
 {
-	if (!capable(CAP_SETPCAP))
+	struct cred *new;
+
+	if (!ns_capable(current_user_ns(), CAP_SETPCAP))
 		return -EPERM;
 	if (!cap_valid(cap))
 		return -EINVAL;
 
+	new = prepare_creds();
+	if (!new)
+		return -ENOMEM;
 	cap_lower(new->cap_bset, cap);
-	return 0;
+	return commit_creds(new);
 }
 
 /**
@@ -839,26 +888,17 @@ static long cap_prctl_drop(struct cred *new, unsigned long cap)
 int cap_task_prctl(int option, unsigned long arg2, unsigned long arg3,
 		   unsigned long arg4, unsigned long arg5)
 {
+	const struct cred *old = current_cred();
 	struct cred *new;
-	long error = 0;
-
-	new = prepare_creds();
-	if (!new)
-		return -ENOMEM;
 
 	switch (option) {
 	case PR_CAPBSET_READ:
-		error = -EINVAL;
 		if (!cap_valid(arg2))
-			goto error;
-		error = !!cap_raised(new->cap_bset, arg2);
-		goto no_change;
+			return -EINVAL;
+		return !!cap_raised(old->cap_bset, arg2);
 
 	case PR_CAPBSET_DROP:
-		error = cap_prctl_drop(new, arg2);
-		if (error < 0)
-			goto error;
-		goto changed;
+		return cap_prctl_drop(arg2);
 
 	/*
 	 * The next four prctl's remain to assist with transitioning a
@@ -880,10 +920,9 @@ int cap_task_prctl(int option, unsigned long arg2, unsigned long arg3,
 	 * capability-based-privilege environment.
 	 */
 	case PR_SET_SECUREBITS:
-		error = -EPERM;
-		if ((((new->securebits & SECURE_ALL_LOCKS) >> 1)
-		     & (new->securebits ^ arg2))			/*[1]*/
-		    || ((new->securebits & SECURE_ALL_LOCKS & ~arg2))	/*[2]*/
+		if ((((old->securebits & SECURE_ALL_LOCKS) >> 1)
+		     & (old->securebits ^ arg2))			/*[1]*/
+		    || ((old->securebits & SECURE_ALL_LOCKS & ~arg2))	/*[2]*/
 		    || (arg2 & ~(SECURE_ALL_LOCKS | SECURE_ALL_BITS))	/*[3]*/
 		    || (cap_capable(current_cred(),
 				    current_cred()->user->user_ns, CAP_SETPCAP,
@@ -897,46 +936,76 @@ int cap_task_prctl(int option, unsigned long arg2, unsigned long arg3,
 			 */
 		    )
 			/* cannot change a locked bit */
-			goto error;
+			return -EPERM;
+
+		new = prepare_creds();
+		if (!new)
+			return -ENOMEM;
 		new->securebits = arg2;
-		goto changed;
+		return commit_creds(new);
 
 	case PR_GET_SECUREBITS:
-		error = new->securebits;
-		goto no_change;
+		return old->securebits;
 
 	case PR_GET_KEEPCAPS:
-		if (issecure(SECURE_KEEP_CAPS))
-			error = 1;
-		goto no_change;
+		return !!issecure(SECURE_KEEP_CAPS);
 
 	case PR_SET_KEEPCAPS:
-		error = -EINVAL;
 		if (arg2 > 1) /* Note, we rely on arg2 being unsigned here */
-			goto error;
-		error = -EPERM;
+			return -EINVAL;
 		if (issecure(SECURE_KEEP_CAPS_LOCKED))
-			goto error;
+			return -EPERM;
+
+		new = prepare_creds();
+		if (!new)
+			return -ENOMEM;
 		if (arg2)
 			new->securebits |= issecure_mask(SECURE_KEEP_CAPS);
 		else
 			new->securebits &= ~issecure_mask(SECURE_KEEP_CAPS);
-		goto changed;
+		return commit_creds(new);
+
+	case PR_CAP_AMBIENT:
+		if (arg2 == PR_CAP_AMBIENT_CLEAR_ALL) {
+			if (arg3 | arg4 | arg5)
+				return -EINVAL;
+
+			new = prepare_creds();
+			if (!new)
+				return -ENOMEM;
+			cap_clear(new->cap_ambient);
+			return commit_creds(new);
+		}
+
+		if (((!cap_valid(arg3)) | arg4 | arg5))
+			return -EINVAL;
+
+		if (arg2 == PR_CAP_AMBIENT_IS_SET) {
+			return !!cap_raised(current_cred()->cap_ambient, arg3);
+		} else if (arg2 != PR_CAP_AMBIENT_RAISE &&
+			   arg2 != PR_CAP_AMBIENT_LOWER) {
+			return -EINVAL;
+		} else {
+			if (arg2 == PR_CAP_AMBIENT_RAISE &&
+			    (!cap_raised(current_cred()->cap_permitted, arg3) ||
+			     !cap_raised(current_cred()->cap_inheritable,
+					 arg3)))
+				return -EPERM;
+
+			new = prepare_creds();
+			if (!new)
+				return -ENOMEM;
+			if (arg2 == PR_CAP_AMBIENT_RAISE)
+				cap_raise(new->cap_ambient, arg3);
+			else
+				cap_lower(new->cap_ambient, arg3);
+			return commit_creds(new);
+		}
 
 	default:
 		/* No functionality available - continue with default */
-		error = -ENOSYS;
-		goto error;
+		return -ENOSYS;
 	}
-
-	/* Functionality provided */
-changed:
-	return commit_creds(new);
-
-no_change:
-error:
-	abort_creds(new);
-	return error;
 }
 
 /**