X-Git-Url: https://err.no/cgi-bin/gitweb.cgi?a=blobdiff_plain;f=kernel%2Fcapability.c;h=0101e847603e675d46cbfd53154455e3ba8943de;hb=37193fb4639fa94f91cbbab1e8aca596300e1d94;hp=39e8193b41ea658f1d67fca1d91edb38e698edea;hpb=26b6f2236615649a0ae6a0de2e9e71a2f9ffeba7;p=linux-2.6

diff --git a/kernel/capability.c b/kernel/capability.c
index 39e8193b41..0101e84760 100644
--- a/kernel/capability.c
+++ b/kernel/capability.c
@@ -53,28 +53,42 @@ static void warn_legacy_capability_use(void)
 }
 
 /*
- * For sys_getproccap() and sys_setproccap(), any of the three
- * capability set pointers may be NULL -- indicating that that set is
- * uninteresting and/or not to be changed.
+ * Version 2 capabilities worked fine, but the linux/capability.h file
+ * that accompanied their introduction encouraged their use without
+ * the necessary user-space source code changes. As such, we have
+ * created a version 3 with equivalent functionality to version 2, but
+ * with a header change to protect legacy source code from using
+ * version 2 when it wanted to use version 1. If your system has code
+ * that trips the following warning, it is using version 2 specific
+ * capabilities and may be doing so insecurely.
+ *
+ * The remedy is to either upgrade your version of libcap (to 2.10+,
+ * if the application is linked against it), or recompile your
+ * application with modern kernel headers and this warning will go
+ * away.
  */
 
-/**
- * sys_capget - get the capabilities of a given process.
- * @header: pointer to struct that contains capability version and
- *	target pid data
- * @dataptr: pointer to struct that contains the effective, permitted,
- *	and inheritable capabilities that are returned
- *
- * Returns 0 on success and < 0 on error.
+static void warn_deprecated_v2(void)
+{
+	static int warned;
+
+	if (!warned) {
+		char name[sizeof(current->comm)];
+
+		printk(KERN_INFO "warning: `%s' uses deprecated v2"
+		       " capabilities in a way that may be insecure.\n",
+		       get_task_comm(name, current));
+		warned = 1;
+	}
+}
+
+/*
+ * Version check. Return the number of u32s in each capability flag
+ * array, or a negative value on error.
  */
-asmlinkage long sys_capget(cap_user_header_t header, cap_user_data_t dataptr)
+static int cap_validate_magic(cap_user_header_t header, unsigned *tocopy)
 {
-	int ret = 0;
-	pid_t pid;
 	__u32 version;
-	struct task_struct *target;
-	unsigned tocopy;
-	kernel_cap_t pE, pI, pP;
 
 	if (get_user(version, &header->version))
 		return -EFAULT;
@@ -82,22 +96,36 @@ asmlinkage long sys_capget(cap_user_header_t header, cap_user_data_t dataptr)
 	switch (version) {
 	case _LINUX_CAPABILITY_VERSION_1:
 		warn_legacy_capability_use();
-		tocopy = _LINUX_CAPABILITY_U32S_1;
+		*tocopy = _LINUX_CAPABILITY_U32S_1;
 		break;
 	case _LINUX_CAPABILITY_VERSION_2:
-		tocopy = _LINUX_CAPABILITY_U32S_2;
+		warn_deprecated_v2();
+		/*
+		 * fall through - v3 is otherwise equivalent to v2.
+		 */
+	case _LINUX_CAPABILITY_VERSION_3:
+		*tocopy = _LINUX_CAPABILITY_U32S_3;
 		break;
 	default:
-		if (put_user(_LINUX_CAPABILITY_VERSION, &header->version))
+		if (put_user((u32)_KERNEL_CAPABILITY_VERSION, &header->version))
 			return -EFAULT;
 		return -EINVAL;
 	}
 
-	if (get_user(pid, &header->pid))
-		return -EFAULT;
+	return 0;
+}
 
-	if (pid < 0)
-		return -EINVAL;
+#ifndef CONFIG_SECURITY_FILE_CAPABILITIES
+
+/*
+ * Without filesystem capability support, we nominally support one process
+ * setting the capabilities of another
+ */
+static inline int cap_get_target_pid(pid_t pid, kernel_cap_t *pEp,
+				     kernel_cap_t *pIp, kernel_cap_t *pPp)
+{
+	struct task_struct *target;
+	int ret;
 
 	spin_lock(&task_capability_lock);
 	read_lock(&tasklist_lock);
@@ -111,48 +139,12 @@ asmlinkage long sys_capget(cap_user_header_t header, cap_user_data_t dataptr)
 	} else
 		target = current;
 
-	ret = security_capget(target, &pE, &pI, &pP);
+	ret = security_capget(target, pEp, pIp, pPp);
 
 out:
 	read_unlock(&tasklist_lock);
 	spin_unlock(&task_capability_lock);
 
-	if (!ret) {
-		struct __user_cap_data_struct kdata[_LINUX_CAPABILITY_U32S];
-		unsigned i;
-
-		for (i = 0; i < tocopy; i++) {
-			kdata[i].effective = pE.cap[i];
-			kdata[i].permitted = pP.cap[i];
-			kdata[i].inheritable = pI.cap[i];
-		}
-
-		/*
-		 * Note, in the case, tocopy < _LINUX_CAPABILITY_U32S,
-		 * we silently drop the upper capabilities here. This
-		 * has the effect of making older libcap
-		 * implementations implicitly drop upper capability
-		 * bits when they perform a: capget/modify/capset
-		 * sequence.
-		 *
-		 * This behavior is considered fail-safe
-		 * behavior. Upgrading the application to a newer
-		 * version of libcap will enable access to the newer
-		 * capabilities.
-		 *
-		 * An alternative would be to return an error here
-		 * (-ERANGE), but that causes legacy applications to
-		 * unexpectidly fail; the capget/modify/capset aborts
-		 * before modification is attempted and the application
-		 * fails.
-		 */
-
-		if (copy_to_user(dataptr, kdata, tocopy
-				 * sizeof(struct __user_cap_data_struct))) {
-			return -EFAULT;
-		}
-	}
-
 	return ret;
 }
 
@@ -161,30 +153,34 @@ out:
  * group.  We call this holding task_capability_lock and tasklist_lock.
  */
 static inline int cap_set_pg(int pgrp_nr, kernel_cap_t *effective,
-			      kernel_cap_t *inheritable,
-			      kernel_cap_t *permitted)
+			     kernel_cap_t *inheritable,
+			     kernel_cap_t *permitted)
 {
 	struct task_struct *g, *target;
 	int ret = -EPERM;
 	int found = 0;
 	struct pid *pgrp;
 
+	spin_lock(&task_capability_lock);
+	read_lock(&tasklist_lock);
+
 	pgrp = find_vpid(pgrp_nr);
 	do_each_pid_task(pgrp, PIDTYPE_PGID, g) {
 		target = g;
 		while_each_thread(g, target) {
 			if (!security_capset_check(target, effective,
-							inheritable,
-							permitted)) {
+						   inheritable, permitted)) {
 				security_capset_set(target, effective,
-							inheritable,
-							permitted);
+						    inheritable, permitted);
 				ret = 0;
 			}
 			found = 1;
 		}
 	} while_each_pid_task(pgrp, PIDTYPE_PGID, g);
 
+	read_unlock(&tasklist_lock);
+	spin_unlock(&task_capability_lock);
+
 	if (!found)
 		ret = 0;
 	return ret;
@@ -195,31 +191,222 @@ static inline int cap_set_pg(int pgrp_nr, kernel_cap_t *effective,
  * and self.  We call this holding task_capability_lock and tasklist_lock.
  */
 static inline int cap_set_all(kernel_cap_t *effective,
-			       kernel_cap_t *inheritable,
-			       kernel_cap_t *permitted)
+			      kernel_cap_t *inheritable,
+			      kernel_cap_t *permitted)
+{
+	struct task_struct *g, *target;
+	int ret = -EPERM;
+	int found = 0;
+
+	spin_lock(&task_capability_lock);
+	read_lock(&tasklist_lock);
+
+	do_each_thread(g, target) {
+		if (target == current
+		    || is_container_init(target->group_leader))
+			continue;
+		found = 1;
+		if (security_capset_check(target, effective, inheritable,
+					  permitted))
+			continue;
+		ret = 0;
+		security_capset_set(target, effective, inheritable, permitted);
+	} while_each_thread(g, target);
+
+	read_unlock(&tasklist_lock);
+	spin_unlock(&task_capability_lock);
+
+	if (!found)
+		ret = 0;
+
+	return ret;
+}
+
+/*
+ * Given the target pid does not refer to the current process we
+ * need more elaborate support... (This support is not present when
+ * filesystem capabilities are configured.)
+ */
+static inline int do_sys_capset_other_tasks(pid_t pid, kernel_cap_t *effective,
+					    kernel_cap_t *inheritable,
+					    kernel_cap_t *permitted)
+{
+	struct task_struct *target;
+	int ret;
+
+	if (!capable(CAP_SETPCAP))
+		return -EPERM;
+
+	if (pid == -1)	          /* all procs other than current and init */
+		return cap_set_all(effective, inheritable, permitted);
+
+	else if (pid < 0)                    /* all procs in process group */
+		return cap_set_pg(-pid, effective, inheritable, permitted);
+
+	/* target != current */
+	spin_lock(&task_capability_lock);
+	read_lock(&tasklist_lock);
+
+	target = find_task_by_vpid(pid);
+	if (!target)
+		ret = -ESRCH;
+	else {
+		ret = security_capset_check(target, effective, inheritable,
+					    permitted);
+
+		/* having verified that the proposed changes are legal,
+		   we now put them into effect. */
+		if (!ret)
+			security_capset_set(target, effective, inheritable,
+					    permitted);
+	}
+
+	read_unlock(&tasklist_lock);
+	spin_unlock(&task_capability_lock);
+
+	return ret;
+}
+
+#else /* ie., def CONFIG_SECURITY_FILE_CAPABILITIES */
+
+/*
+ * If we have configured with filesystem capability support, then the
+ * only thing that can change the capabilities of the current process
+ * is the current process. As such, we can't be in this code at the
+ * same time as we are in the process of setting capabilities in this
+ * process. The net result is that we can limit our use of locks to
+ * when we are reading the caps of another process.
+ */
+static inline int cap_get_target_pid(pid_t pid, kernel_cap_t *pEp,
+				     kernel_cap_t *pIp, kernel_cap_t *pPp)
+{
+	int ret;
+
+	if (pid && (pid != task_pid_vnr(current))) {
+		struct task_struct *target;
+
+		spin_lock(&task_capability_lock);
+		read_lock(&tasklist_lock);
+
+		target = find_task_by_vpid(pid);
+		if (!target)
+			ret = -ESRCH;
+		else
+			ret = security_capget(target, pEp, pIp, pPp);
+
+		read_unlock(&tasklist_lock);
+		spin_unlock(&task_capability_lock);
+	} else
+		ret = security_capget(current, pEp, pIp, pPp);
+
+	return ret;
+}
+
+/*
+ * With filesystem capability support configured, the kernel does not
+ * permit the changing of capabilities in one process by another
+ * process. (CAP_SETPCAP has much less broad semantics when configured
+ * this way.)
+ */
+static inline int do_sys_capset_other_tasks(pid_t pid,
+					    kernel_cap_t *effective,
+					    kernel_cap_t *inheritable,
+					    kernel_cap_t *permitted)
+{
+	return -EPERM;
+}
+
+#endif /* ie., ndef CONFIG_SECURITY_FILE_CAPABILITIES */
+
+/*
+ * Atomically modify the effective capabilities returning the original
+ * value. No permission check is performed here - it is assumed that the
+ * caller is permitted to set the desired effective capabilities.
+ */
+kernel_cap_t cap_set_effective(const kernel_cap_t pE_new)
 {
-     struct task_struct *g, *target;
-     int ret = -EPERM;
-     int found = 0;
-
-     do_each_thread(g, target) {
-             if (target == current || is_container_init(target->group_leader))
-                     continue;
-             found = 1;
-	     if (security_capset_check(target, effective, inheritable,
-						permitted))
-		     continue;
-	     ret = 0;
-	     security_capset_set(target, effective, inheritable, permitted);
-     } while_each_thread(g, target);
-
-     if (!found)
-	     ret = 0;
-     return ret;
+	kernel_cap_t pE_old;
+
+	spin_lock(&task_capability_lock);
+
+	pE_old = current->cap_effective;
+	current->cap_effective = pE_new;
+
+	spin_unlock(&task_capability_lock);
+
+	return pE_old;
 }
 
+EXPORT_SYMBOL(cap_set_effective);
+
 /**
- * sys_capset - set capabilities for a process or a group of processes
+ * sys_capget - get the capabilities of a given process.
+ * @header: pointer to struct that contains capability version and
+ *	target pid data
+ * @dataptr: pointer to struct that contains the effective, permitted,
+ *	and inheritable capabilities that are returned
+ *
+ * Returns 0 on success and < 0 on error.
+ */
+asmlinkage long sys_capget(cap_user_header_t header, cap_user_data_t dataptr)
+{
+	int ret = 0;
+	pid_t pid;
+	unsigned tocopy;
+	kernel_cap_t pE, pI, pP;
+
+	ret = cap_validate_magic(header, &tocopy);
+	if (ret != 0)
+		return ret;
+
+	if (get_user(pid, &header->pid))
+		return -EFAULT;
+
+	if (pid < 0)
+		return -EINVAL;
+
+	ret = cap_get_target_pid(pid, &pE, &pI, &pP);
+
+	if (!ret) {
+		struct __user_cap_data_struct kdata[_KERNEL_CAPABILITY_U32S];
+		unsigned i;
+
+		for (i = 0; i < tocopy; i++) {
+			kdata[i].effective = pE.cap[i];
+			kdata[i].permitted = pP.cap[i];
+			kdata[i].inheritable = pI.cap[i];
+		}
+
+		/*
+		 * Note, in the case, tocopy < _KERNEL_CAPABILITY_U32S,
+		 * we silently drop the upper capabilities here. This
+		 * has the effect of making older libcap
+		 * implementations implicitly drop upper capability
+		 * bits when they perform a: capget/modify/capset
+		 * sequence.
+		 *
+		 * This behavior is considered fail-safe
+		 * behavior. Upgrading the application to a newer
+		 * version of libcap will enable access to the newer
+		 * capabilities.
+		 *
+		 * An alternative would be to return an error here
+		 * (-ERANGE), but that causes legacy applications to
+		 * unexpectidly fail; the capget/modify/capset aborts
+		 * before modification is attempted and the application
+		 * fails.
+		 */
+		if (copy_to_user(dataptr, kdata, tocopy
+				 * sizeof(struct __user_cap_data_struct))) {
+			return -EFAULT;
+		}
+	}
+
+	return ret;
+}
+
+/**
+ * sys_capset - set capabilities for a process or (*) a group of processes
  * @header: pointer to struct that contains capability version and
  *	target pid data
  * @data: pointer to struct that contains the effective, permitted,
@@ -240,37 +427,19 @@ static inline int cap_set_all(kernel_cap_t *effective,
  */
 asmlinkage long sys_capset(cap_user_header_t header, const cap_user_data_t data)
 {
-	struct __user_cap_data_struct kdata[_LINUX_CAPABILITY_U32S];
+	struct __user_cap_data_struct kdata[_KERNEL_CAPABILITY_U32S];
 	unsigned i, tocopy;
 	kernel_cap_t inheritable, permitted, effective;
-	__u32 version;
-	struct task_struct *target;
 	int ret;
 	pid_t pid;
 
-	if (get_user(version, &header->version))
-		return -EFAULT;
-
-	switch (version) {
-	case _LINUX_CAPABILITY_VERSION_1:
-		warn_legacy_capability_use();
-		tocopy = _LINUX_CAPABILITY_U32S_1;
-		break;
-	case _LINUX_CAPABILITY_VERSION_2:
-		tocopy = _LINUX_CAPABILITY_U32S_2;
-		break;
-	default:
-		if (put_user(_LINUX_CAPABILITY_VERSION, &header->version))
-			return -EFAULT;
-		return -EINVAL;
-	}
+	ret = cap_validate_magic(header, &tocopy);
+	if (ret != 0)
+		return ret;
 
 	if (get_user(pid, &header->pid))
 		return -EFAULT;
 
-	if (pid && pid != task_pid_vnr(current) && !capable(CAP_SETPCAP))
-		return -EPERM;
-
 	if (copy_from_user(&kdata, data, tocopy
 			   * sizeof(struct __user_cap_data_struct))) {
 		return -EFAULT;
@@ -281,47 +450,38 @@ asmlinkage long sys_capset(cap_user_header_t header, const cap_user_data_t data)
 		permitted.cap[i] = kdata[i].permitted;
 		inheritable.cap[i] = kdata[i].inheritable;
 	}
-	while (i < _LINUX_CAPABILITY_U32S) {
+	while (i < _KERNEL_CAPABILITY_U32S) {
 		effective.cap[i] = 0;
 		permitted.cap[i] = 0;
 		inheritable.cap[i] = 0;
 		i++;
 	}
 
-	spin_lock(&task_capability_lock);
-	read_lock(&tasklist_lock);
-
-	if (pid > 0 && pid != task_pid_vnr(current)) {
-		target = find_task_by_vpid(pid);
-		if (!target) {
-			ret = -ESRCH;
-			goto out;
-		}
-	} else
-		target = current;
-
-	ret = 0;
-
-	/* having verified that the proposed changes are legal,
-	   we now put them into effect. */
-	if (pid < 0) {
-		if (pid == -1)	/* all procs other than current and init */
-			ret = cap_set_all(&effective, &inheritable, &permitted);
+	if (pid && (pid != task_pid_vnr(current)))
+		ret = do_sys_capset_other_tasks(pid, &effective, &inheritable,
+						&permitted);
+	else {
+		/*
+		 * This lock is required even when filesystem
+		 * capability support is configured - it protects the
+		 * sys_capget() call from returning incorrect data in
+		 * the case that the targeted process is not the
+		 * current one.
+		 */
+		spin_lock(&task_capability_lock);
 
-		else		/* all procs in process group */
-			ret = cap_set_pg(-pid, &effective, &inheritable,
-					 &permitted);
-	} else {
-		ret = security_capset_check(target, &effective, &inheritable,
+		ret = security_capset_check(current, &effective, &inheritable,
 					    &permitted);
+		/*
+		 * Having verified that the proposed changes are
+		 * legal, we now put them into effect.
+		 */
 		if (!ret)
-			security_capset_set(target, &effective, &inheritable,
+			security_capset_set(current, &effective, &inheritable,
 					    &permitted);
+		spin_unlock(&task_capability_lock);
 	}
 
-out:
-	read_unlock(&tasklist_lock);
-	spin_unlock(&task_capability_lock);
 
 	return ret;
 }