File-copy from v4.4.100
This is the result of 'cp' from a linux-stable tree with the 'v4.4.100'
tag checked out (commit 26d6298789e695c9f627ce49a7bbd2286405798a) on
git://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git
Please refer to that tree for all history prior to this point.
Change-Id: I8a9ee2aea93cd29c52c847d0ce33091a73ae6afe
diff --git a/security/commoncap.c b/security/commoncap.c
new file mode 100644
index 0000000..48071ed
--- /dev/null
+++ b/security/commoncap.c
@@ -0,0 +1,1096 @@
+/* Common capabilities, needed by capability.o.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ */
+
+#include <linux/capability.h>
+#include <linux/audit.h>
+#include <linux/module.h>
+#include <linux/init.h>
+#include <linux/kernel.h>
+#include <linux/lsm_hooks.h>
+#include <linux/file.h>
+#include <linux/mm.h>
+#include <linux/mman.h>
+#include <linux/pagemap.h>
+#include <linux/swap.h>
+#include <linux/skbuff.h>
+#include <linux/netlink.h>
+#include <linux/ptrace.h>
+#include <linux/xattr.h>
+#include <linux/hugetlb.h>
+#include <linux/mount.h>
+#include <linux/sched.h>
+#include <linux/prctl.h>
+#include <linux/securebits.h>
+#include <linux/user_namespace.h>
+#include <linux/binfmts.h>
+#include <linux/personality.h>
+
+/*
+ * If a non-root user executes a setuid-root binary in
+ * !secure(SECURE_NOROOT) mode, then we raise capabilities.
+ * However if fE is also set, then the intent is for only
+ * the file capabilities to be applied, and the setuid-root
+ * bit is left on either to change the uid (plausible) or
+ * to get full privilege on a kernel without file capabilities
+ * support. So in that case we do not raise capabilities.
+ *
+ * Warn if that happens, once per boot.
+ */
+static void warn_setuid_and_fcaps_mixed(const char *fname)
+{
+ static int warned;
+ if (!warned) {
+ printk(KERN_INFO "warning: `%s' has both setuid-root and"
+ " effective capabilities. Therefore not raising all"
+ " capabilities.\n", fname);
+ warned = 1;
+ }
+}
+
+/**
+ * cap_capable - Determine whether a task has a particular effective capability
+ * @cred: The credentials to use
+ * @ns: The user namespace in which we need the capability
+ * @cap: The capability to check for
+ * @audit: Whether to write an audit message or not
+ *
+ * Determine whether the nominated task has the specified capability amongst
+ * its effective set, returning 0 if it does, -ve if it does not.
+ *
+ * NOTE WELL: cap_has_capability() cannot be used like the kernel's capable()
+ * and has_capability() functions. That is, it has the reverse semantics:
+ * cap_has_capability() returns 0 when a task has a capability, but the
+ * kernel's capable() and has_capability() returns 1 for this case.
+ */
+int cap_capable(const struct cred *cred, struct user_namespace *targ_ns,
+ int cap, int audit)
+{
+ struct user_namespace *ns = targ_ns;
+
+ /* See if cred has the capability in the target user namespace
+ * by examining the target user namespace and all of the target
+ * user namespace's parents.
+ */
+ for (;;) {
+ /* Do we have the necessary capabilities? */
+ if (ns == cred->user_ns)
+ return cap_raised(cred->cap_effective, cap) ? 0 : -EPERM;
+
+ /* Have we tried all of the parent namespaces? */
+ if (ns == &init_user_ns)
+ return -EPERM;
+
+ /*
+ * The owner of the user namespace in the parent of the
+ * user namespace has all caps.
+ */
+ if ((ns->parent == cred->user_ns) && uid_eq(ns->owner, cred->euid))
+ return 0;
+
+ /*
+ * If you have a capability in a parent user ns, then you have
+ * it over all children user namespaces as well.
+ */
+ ns = ns->parent;
+ }
+
+ /* We never get here */
+}
+
+/**
+ * cap_settime - Determine whether the current process may set the system clock
+ * @ts: The time to set
+ * @tz: The timezone to set
+ *
+ * Determine whether the current process may set the system clock and timezone
+ * information, returning 0 if permission granted, -ve if denied.
+ */
+int cap_settime(const struct timespec *ts, const struct timezone *tz)
+{
+ if (!capable(CAP_SYS_TIME))
+ return -EPERM;
+ return 0;
+}
+
+/**
+ * cap_ptrace_access_check - Determine whether the current process may access
+ * another
+ * @child: The process to be accessed
+ * @mode: The mode of attachment.
+ *
+ * If we are in the same or an ancestor user_ns and have all the target
+ * task's capabilities, then ptrace access is allowed.
+ * If we have the ptrace capability to the target user_ns, then ptrace
+ * access is allowed.
+ * Else denied.
+ *
+ * Determine whether a process may access another, returning 0 if permission
+ * granted, -ve if denied.
+ */
+int cap_ptrace_access_check(struct task_struct *child, unsigned int mode)
+{
+ int ret = 0;
+ const struct cred *cred, *child_cred;
+ const kernel_cap_t *caller_caps;
+
+ rcu_read_lock();
+ cred = current_cred();
+ child_cred = __task_cred(child);
+ if (mode & PTRACE_MODE_FSCREDS)
+ caller_caps = &cred->cap_effective;
+ else
+ caller_caps = &cred->cap_permitted;
+ if (cred->user_ns == child_cred->user_ns &&
+ cap_issubset(child_cred->cap_permitted, *caller_caps))
+ goto out;
+ if (ns_capable(child_cred->user_ns, CAP_SYS_PTRACE))
+ goto out;
+ ret = -EPERM;
+out:
+ rcu_read_unlock();
+ return ret;
+}
+
+/**
+ * cap_ptrace_traceme - Determine whether another process may trace the current
+ * @parent: The task proposed to be the tracer
+ *
+ * If parent is in the same or an ancestor user_ns and has all current's
+ * capabilities, then ptrace access is allowed.
+ * If parent has the ptrace capability to current's user_ns, then ptrace
+ * access is allowed.
+ * Else denied.
+ *
+ * Determine whether the nominated task is permitted to trace the current
+ * process, returning 0 if permission is granted, -ve if denied.
+ */
+int cap_ptrace_traceme(struct task_struct *parent)
+{
+ int ret = 0;
+ const struct cred *cred, *child_cred;
+
+ rcu_read_lock();
+ cred = __task_cred(parent);
+ child_cred = current_cred();
+ if (cred->user_ns == child_cred->user_ns &&
+ cap_issubset(child_cred->cap_permitted, cred->cap_permitted))
+ goto out;
+ if (has_ns_capability(parent, child_cred->user_ns, CAP_SYS_PTRACE))
+ goto out;
+ ret = -EPERM;
+out:
+ rcu_read_unlock();
+ return ret;
+}
+
+/**
+ * cap_capget - Retrieve a task's capability sets
+ * @target: The task from which to retrieve the capability sets
+ * @effective: The place to record the effective set
+ * @inheritable: The place to record the inheritable set
+ * @permitted: The place to record the permitted set
+ *
+ * This function retrieves the capabilities of the nominated task and returns
+ * them to the caller.
+ */
+int cap_capget(struct task_struct *target, kernel_cap_t *effective,
+ kernel_cap_t *inheritable, kernel_cap_t *permitted)
+{
+ const struct cred *cred;
+
+ /* Derived from kernel/capability.c:sys_capget. */
+ rcu_read_lock();
+ cred = __task_cred(target);
+ *effective = cred->cap_effective;
+ *inheritable = cred->cap_inheritable;
+ *permitted = cred->cap_permitted;
+ rcu_read_unlock();
+ return 0;
+}
+
+/*
+ * Determine whether the inheritable capabilities are limited to the old
+ * permitted set. Returns 1 if they are limited, 0 if they are not.
+ */
+static inline int cap_inh_is_capped(void)
+{
+
+ /* they are so limited unless the current task has the CAP_SETPCAP
+ * capability
+ */
+ if (cap_capable(current_cred(), current_cred()->user_ns,
+ CAP_SETPCAP, SECURITY_CAP_AUDIT) == 0)
+ return 0;
+ return 1;
+}
+
+/**
+ * cap_capset - Validate and apply proposed changes to current's capabilities
+ * @new: The proposed new credentials; alterations should be made here
+ * @old: The current task's current credentials
+ * @effective: A pointer to the proposed new effective capabilities set
+ * @inheritable: A pointer to the proposed new inheritable capabilities set
+ * @permitted: A pointer to the proposed new permitted capabilities set
+ *
+ * This function validates and applies a proposed mass change to the current
+ * process's capability sets. The changes are made to the proposed new
+ * credentials, and assuming no error, will be committed by the caller of LSM.
+ */
+int cap_capset(struct cred *new,
+ const struct cred *old,
+ const kernel_cap_t *effective,
+ const kernel_cap_t *inheritable,
+ const kernel_cap_t *permitted)
+{
+ if (cap_inh_is_capped() &&
+ !cap_issubset(*inheritable,
+ cap_combine(old->cap_inheritable,
+ old->cap_permitted)))
+ /* incapable of using this inheritable set */
+ return -EPERM;
+
+ if (!cap_issubset(*inheritable,
+ cap_combine(old->cap_inheritable,
+ old->cap_bset)))
+ /* no new pI capabilities outside bounding set */
+ return -EPERM;
+
+ /* verify restrictions on target's new Permitted set */
+ if (!cap_issubset(*permitted, old->cap_permitted))
+ return -EPERM;
+
+ /* verify the _new_Effective_ is a subset of the _new_Permitted_ */
+ if (!cap_issubset(*effective, *permitted))
+ return -EPERM;
+
+ 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;
+}
+
+/*
+ * Clear proposed capability sets for execve().
+ */
+static inline void bprm_clear_caps(struct linux_binprm *bprm)
+{
+ cap_clear(bprm->cred->cap_permitted);
+ bprm->cap_effective = false;
+}
+
+/**
+ * cap_inode_need_killpriv - Determine if inode change affects privileges
+ * @dentry: The inode/dentry in being changed with change marked ATTR_KILL_PRIV
+ *
+ * Determine if an inode having a change applied that's marked ATTR_KILL_PRIV
+ * affects the security markings on that inode, and if it is, should
+ * inode_killpriv() be invoked or the change rejected?
+ *
+ * Returns 0 if granted; +ve if granted, but inode_killpriv() is required; and
+ * -ve to deny the change.
+ */
+int cap_inode_need_killpriv(struct dentry *dentry)
+{
+ struct inode *inode = d_backing_inode(dentry);
+ int error;
+
+ if (!inode->i_op->getxattr)
+ return 0;
+
+ error = inode->i_op->getxattr(dentry, XATTR_NAME_CAPS, NULL, 0);
+ if (error <= 0)
+ return 0;
+ return 1;
+}
+
+/**
+ * cap_inode_killpriv - Erase the security markings on an inode
+ * @dentry: The inode/dentry to alter
+ *
+ * Erase the privilege-enhancing security markings on an inode.
+ *
+ * Returns 0 if successful, -ve on error.
+ */
+int cap_inode_killpriv(struct dentry *dentry)
+{
+ struct inode *inode = d_backing_inode(dentry);
+
+ if (!inode->i_op->removexattr)
+ return 0;
+
+ return inode->i_op->removexattr(dentry, XATTR_NAME_CAPS);
+}
+
+/*
+ * Calculate the new process capability sets from the capability sets attached
+ * to a file.
+ */
+static inline int bprm_caps_from_vfs_caps(struct cpu_vfs_cap_data *caps,
+ struct linux_binprm *bprm,
+ bool *effective,
+ bool *has_cap)
+{
+ struct cred *new = bprm->cred;
+ unsigned i;
+ int ret = 0;
+
+ if (caps->magic_etc & VFS_CAP_FLAGS_EFFECTIVE)
+ *effective = true;
+
+ if (caps->magic_etc & VFS_CAP_REVISION_MASK)
+ *has_cap = true;
+
+ CAP_FOR_EACH_U32(i) {
+ __u32 permitted = caps->permitted.cap[i];
+ __u32 inheritable = caps->inheritable.cap[i];
+
+ /*
+ * pP' = (X & fP) | (pI & fI)
+ * The addition of pA' is handled later.
+ */
+ new->cap_permitted.cap[i] =
+ (new->cap_bset.cap[i] & permitted) |
+ (new->cap_inheritable.cap[i] & inheritable);
+
+ if (permitted & ~new->cap_permitted.cap[i])
+ /* insufficient to execute correctly */
+ ret = -EPERM;
+ }
+
+ /*
+ * For legacy apps, with no internal support for recognizing they
+ * do not have enough capabilities, we return an error if they are
+ * missing some "forced" (aka file-permitted) capabilities.
+ */
+ return *effective ? ret : 0;
+}
+
+/*
+ * Extract the on-exec-apply capability sets for an executable file.
+ */
+int get_vfs_caps_from_disk(const struct dentry *dentry, struct cpu_vfs_cap_data *cpu_caps)
+{
+ struct inode *inode = d_backing_inode(dentry);
+ __u32 magic_etc;
+ unsigned tocopy, i;
+ int size;
+ struct vfs_cap_data caps;
+
+ memset(cpu_caps, 0, sizeof(struct cpu_vfs_cap_data));
+
+ if (!inode || !inode->i_op->getxattr)
+ return -ENODATA;
+
+ size = inode->i_op->getxattr((struct dentry *)dentry, XATTR_NAME_CAPS, &caps,
+ XATTR_CAPS_SZ);
+ if (size == -ENODATA || size == -EOPNOTSUPP)
+ /* no data, that's ok */
+ return -ENODATA;
+ if (size < 0)
+ return size;
+
+ if (size < sizeof(magic_etc))
+ return -EINVAL;
+
+ cpu_caps->magic_etc = magic_etc = le32_to_cpu(caps.magic_etc);
+
+ switch (magic_etc & VFS_CAP_REVISION_MASK) {
+ case VFS_CAP_REVISION_1:
+ if (size != XATTR_CAPS_SZ_1)
+ return -EINVAL;
+ tocopy = VFS_CAP_U32_1;
+ break;
+ case VFS_CAP_REVISION_2:
+ if (size != XATTR_CAPS_SZ_2)
+ return -EINVAL;
+ tocopy = VFS_CAP_U32_2;
+ break;
+ default:
+ return -EINVAL;
+ }
+
+ CAP_FOR_EACH_U32(i) {
+ if (i >= tocopy)
+ break;
+ cpu_caps->permitted.cap[i] = le32_to_cpu(caps.data[i].permitted);
+ cpu_caps->inheritable.cap[i] = le32_to_cpu(caps.data[i].inheritable);
+ }
+
+ cpu_caps->permitted.cap[CAP_LAST_U32] &= CAP_LAST_U32_VALID_MASK;
+ cpu_caps->inheritable.cap[CAP_LAST_U32] &= CAP_LAST_U32_VALID_MASK;
+
+ return 0;
+}
+
+/*
+ * Attempt to get the on-exec apply capability sets for an executable file from
+ * its xattrs and, if present, apply them to the proposed credentials being
+ * constructed by execve().
+ */
+static int get_file_caps(struct linux_binprm *bprm, bool *effective, bool *has_cap)
+{
+ int rc = 0;
+ struct cpu_vfs_cap_data vcaps;
+
+ bprm_clear_caps(bprm);
+
+ if (!file_caps_enabled)
+ return 0;
+
+ if (bprm->file->f_path.mnt->mnt_flags & MNT_NOSUID)
+ return 0;
+
+ rc = get_vfs_caps_from_disk(bprm->file->f_path.dentry, &vcaps);
+ if (rc < 0) {
+ if (rc == -EINVAL)
+ printk(KERN_NOTICE "%s: get_vfs_caps_from_disk returned %d for %s\n",
+ __func__, rc, bprm->filename);
+ else if (rc == -ENODATA)
+ rc = 0;
+ goto out;
+ }
+
+ rc = bprm_caps_from_vfs_caps(&vcaps, bprm, effective, has_cap);
+ if (rc == -EINVAL)
+ printk(KERN_NOTICE "%s: cap_from_disk returned %d for %s\n",
+ __func__, rc, bprm->filename);
+
+out:
+ if (rc)
+ bprm_clear_caps(bprm);
+
+ return rc;
+}
+
+/**
+ * cap_bprm_set_creds - Set up the proposed credentials for execve().
+ * @bprm: The execution parameters, including the proposed creds
+ *
+ * Set up the proposed credentials for a new execution context being
+ * constructed by execve(). The proposed creds in @bprm->cred is altered,
+ * which won't take effect immediately. Returns 0 if successful, -ve on error.
+ */
+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, is_setid;
+ int ret;
+ kuid_t root_uid;
+
+ if (WARN_ON(!cap_ambient_invariant_ok(old)))
+ return -EPERM;
+
+ effective = false;
+ ret = get_file_caps(bprm, &effective, &has_cap);
+ if (ret < 0)
+ return ret;
+
+ root_uid = make_kuid(new->user_ns, 0);
+
+ if (!issecure(SECURE_NOROOT)) {
+ /*
+ * If the legacy file capability is set, then don't set privs
+ * for a setuid root binary run by a non-root user. Do set it
+ * for a root user just to cause least surprise to an admin.
+ */
+ if (has_cap && !uid_eq(new->uid, root_uid) && uid_eq(new->euid, root_uid)) {
+ warn_setuid_and_fcaps_mixed(bprm->filename);
+ goto skip;
+ }
+ /*
+ * To support inheritance of root-permissions and suid-root
+ * executables under compatibility mode, we override the
+ * capability sets for the file.
+ *
+ * If only the real uid is 0, we do not set the effective bit.
+ */
+ if (uid_eq(new->euid, root_uid) || uid_eq(new->uid, root_uid)) {
+ /* pP' = (cap_bset & ~0) | (pI & ~0) */
+ new->cap_permitted = cap_combine(old->cap_bset,
+ old->cap_inheritable);
+ }
+ if (uid_eq(new->euid, root_uid))
+ effective = true;
+ }
+skip:
+
+ /* if we have fs caps, clear dangerous personality flags */
+ if (!cap_issubset(new->cap_permitted, old->cap_permitted))
+ bprm->per_clear |= PER_CLEAR_ON_SETID;
+
+
+ /* Don't let someone trace a set[ug]id/setpcap binary with the revised
+ * credentials unless they have the appropriate permit.
+ *
+ * In addition, if NO_NEW_PRIVS, then ensure we get no new privs.
+ */
+ is_setid = !uid_eq(new->euid, old->uid) || !gid_eq(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 */
+ if (!capable(CAP_SETUID) ||
+ (bprm->unsafe & LSM_UNSAFE_NO_NEW_PRIVS)) {
+ new->euid = new->uid;
+ new->egid = new->gid;
+ }
+ new->cap_permitted = cap_intersect(new->cap_permitted,
+ old->cap_permitted);
+ }
+
+ 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
+ new->cap_effective = new->cap_ambient;
+
+ if (WARN_ON(!cap_ambient_invariant_ok(new)))
+ return -EPERM;
+
+ bprm->cap_effective = effective;
+
+ /*
+ * Audit candidate if current->cap_effective is set
+ *
+ * We do not bother to audit if 3 things are true:
+ * 1) cap_effective has all caps
+ * 2) we are root
+ * 3) root is supposed to have all caps (SECURE_NOROOT)
+ * Since this is just a normal root execing a process.
+ *
+ * Number 1 above might fail if you don't have a full bset, but I think
+ * that is interesting information to audit.
+ */
+ if (!cap_issubset(new->cap_effective, new->cap_ambient)) {
+ if (!cap_issubset(CAP_FULL_SET, new->cap_effective) ||
+ !uid_eq(new->euid, root_uid) || !uid_eq(new->uid, root_uid) ||
+ issecure(SECURE_NOROOT)) {
+ ret = audit_log_bprm_fcaps(bprm, new, old);
+ if (ret < 0)
+ return ret;
+ }
+ }
+
+ new->securebits &= ~issecure_mask(SECURE_KEEP_CAPS);
+
+ if (WARN_ON(!cap_ambient_invariant_ok(new)))
+ return -EPERM;
+
+ return 0;
+}
+
+/**
+ * cap_bprm_secureexec - Determine whether a secure execution is required
+ * @bprm: The execution parameters
+ *
+ * Determine whether a secure execution is required, return 1 if it is, and 0
+ * if it is not.
+ *
+ * The credentials have been committed by this point, and so are no longer
+ * available through @bprm->cred.
+ */
+int cap_bprm_secureexec(struct linux_binprm *bprm)
+{
+ const struct cred *cred = current_cred();
+ kuid_t root_uid = make_kuid(cred->user_ns, 0);
+
+ if (!uid_eq(cred->uid, root_uid)) {
+ if (bprm->cap_effective)
+ return 1;
+ if (!cap_issubset(cred->cap_permitted, cred->cap_ambient))
+ return 1;
+ }
+
+ return (!uid_eq(cred->euid, cred->uid) ||
+ !gid_eq(cred->egid, cred->gid));
+}
+
+/**
+ * cap_inode_setxattr - Determine whether an xattr may be altered
+ * @dentry: The inode/dentry being altered
+ * @name: The name of the xattr to be changed
+ * @value: The value that the xattr will be changed to
+ * @size: The size of value
+ * @flags: The replacement flag
+ *
+ * Determine whether an xattr may be altered or set on an inode, returning 0 if
+ * permission is granted, -ve if denied.
+ *
+ * This is used to make sure security xattrs don't get updated or set by those
+ * who aren't privileged to do so.
+ */
+int cap_inode_setxattr(struct dentry *dentry, const char *name,
+ const void *value, size_t size, int flags)
+{
+ if (!strcmp(name, XATTR_NAME_CAPS)) {
+ if (!capable(CAP_SETFCAP))
+ return -EPERM;
+ return 0;
+ }
+
+ if (!strncmp(name, XATTR_SECURITY_PREFIX,
+ sizeof(XATTR_SECURITY_PREFIX) - 1) &&
+ !capable(CAP_SYS_ADMIN))
+ return -EPERM;
+ return 0;
+}
+
+/**
+ * cap_inode_removexattr - Determine whether an xattr may be removed
+ * @dentry: The inode/dentry being altered
+ * @name: The name of the xattr to be changed
+ *
+ * Determine whether an xattr may be removed from an inode, returning 0 if
+ * permission is granted, -ve if denied.
+ *
+ * This is used to make sure security xattrs don't get removed by those who
+ * aren't privileged to remove them.
+ */
+int cap_inode_removexattr(struct dentry *dentry, const char *name)
+{
+ if (!strcmp(name, XATTR_NAME_CAPS)) {
+ if (!capable(CAP_SETFCAP))
+ return -EPERM;
+ return 0;
+ }
+
+ if (!strncmp(name, XATTR_SECURITY_PREFIX,
+ sizeof(XATTR_SECURITY_PREFIX) - 1) &&
+ !capable(CAP_SYS_ADMIN))
+ return -EPERM;
+ return 0;
+}
+
+/*
+ * cap_emulate_setxuid() fixes the effective / permitted capabilities of
+ * a process after a call to setuid, setreuid, or setresuid.
+ *
+ * 1) When set*uiding _from_ one of {r,e,s}uid == 0 _to_ all of
+ * {r,e,s}uid != 0, the permitted and effective capabilities are
+ * cleared.
+ *
+ * 2) When set*uiding _from_ euid == 0 _to_ euid != 0, the effective
+ * capabilities of the process are cleared.
+ *
+ * 3) When set*uiding _from_ euid != 0 _to_ euid == 0, the effective
+ * capabilities are set to the permitted capabilities.
+ *
+ * fsuid is handled elsewhere. fsuid == 0 and {r,e,s}uid!= 0 should
+ * never happen.
+ *
+ * -astor
+ *
+ * cevans - New behaviour, Oct '99
+ * A process may, via prctl(), elect to keep its capabilities when it
+ * calls setuid() and switches away from uid==0. Both permitted and
+ * effective sets will be retained.
+ * Without this change, it was impossible for a daemon to drop only some
+ * of its privilege. The call to setuid(!=0) would drop all privileges!
+ * Keeping uid 0 is not an option because uid 0 owns too many vital
+ * files..
+ * Thanks to Olaf Kirch and Peter Benie for spotting this.
+ */
+static inline void cap_emulate_setxuid(struct cred *new, const struct cred *old)
+{
+ kuid_t root_uid = make_kuid(old->user_ns, 0);
+
+ if ((uid_eq(old->uid, root_uid) ||
+ uid_eq(old->euid, root_uid) ||
+ uid_eq(old->suid, root_uid)) &&
+ (!uid_eq(new->uid, root_uid) &&
+ !uid_eq(new->euid, root_uid) &&
+ !uid_eq(new->suid, root_uid))) {
+ 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 (uid_eq(old->euid, root_uid) && !uid_eq(new->euid, root_uid))
+ cap_clear(new->cap_effective);
+ if (!uid_eq(old->euid, root_uid) && uid_eq(new->euid, root_uid))
+ new->cap_effective = new->cap_permitted;
+}
+
+/**
+ * cap_task_fix_setuid - Fix up the results of setuid() call
+ * @new: The proposed credentials
+ * @old: The current task's current credentials
+ * @flags: Indications of what has changed
+ *
+ * Fix up the results of setuid() call before the credential changes are
+ * actually applied, returning 0 to grant the changes, -ve to deny them.
+ */
+int cap_task_fix_setuid(struct cred *new, const struct cred *old, int flags)
+{
+ switch (flags) {
+ case LSM_SETID_RE:
+ case LSM_SETID_ID:
+ case LSM_SETID_RES:
+ /* juggle the capabilities to follow [RES]UID changes unless
+ * otherwise suppressed */
+ if (!issecure(SECURE_NO_SETUID_FIXUP))
+ cap_emulate_setxuid(new, old);
+ break;
+
+ case LSM_SETID_FS:
+ /* juggle the capabilties to follow FSUID changes, unless
+ * otherwise suppressed
+ *
+ * FIXME - is fsuser used for all CAP_FS_MASK capabilities?
+ * if not, we might be a bit too harsh here.
+ */
+ if (!issecure(SECURE_NO_SETUID_FIXUP)) {
+ kuid_t root_uid = make_kuid(old->user_ns, 0);
+ if (uid_eq(old->fsuid, root_uid) && !uid_eq(new->fsuid, root_uid))
+ new->cap_effective =
+ cap_drop_fs_set(new->cap_effective);
+
+ if (!uid_eq(old->fsuid, root_uid) && uid_eq(new->fsuid, root_uid))
+ new->cap_effective =
+ cap_raise_fs_set(new->cap_effective,
+ new->cap_permitted);
+ }
+ break;
+
+ default:
+ return -EINVAL;
+ }
+
+ return 0;
+}
+
+/*
+ * Rationale: code calling task_setscheduler, task_setioprio, and
+ * task_setnice, assumes that
+ * . if capable(cap_sys_nice), then those actions should be allowed
+ * . if not capable(cap_sys_nice), but acting on your own processes,
+ * then those actions should be allowed
+ * This is insufficient now since you can call code without suid, but
+ * yet with increased caps.
+ * So we check for increased caps on the target process.
+ */
+static int cap_safe_nice(struct task_struct *p)
+{
+ int is_subset, ret = 0;
+
+ rcu_read_lock();
+ is_subset = cap_issubset(__task_cred(p)->cap_permitted,
+ current_cred()->cap_permitted);
+ if (!is_subset && !ns_capable(__task_cred(p)->user_ns, CAP_SYS_NICE))
+ ret = -EPERM;
+ rcu_read_unlock();
+
+ return ret;
+}
+
+/**
+ * cap_task_setscheduler - Detemine if scheduler policy change is permitted
+ * @p: The task to affect
+ *
+ * Detemine if the requested scheduler policy change is permitted for the
+ * specified task, returning 0 if permission is granted, -ve if denied.
+ */
+int cap_task_setscheduler(struct task_struct *p)
+{
+ return cap_safe_nice(p);
+}
+
+/**
+ * cap_task_ioprio - Detemine if I/O priority change is permitted
+ * @p: The task to affect
+ * @ioprio: The I/O priority to set
+ *
+ * Detemine if the requested I/O priority change is permitted for the specified
+ * task, returning 0 if permission is granted, -ve if denied.
+ */
+int cap_task_setioprio(struct task_struct *p, int ioprio)
+{
+ return cap_safe_nice(p);
+}
+
+/**
+ * cap_task_ioprio - Detemine if task priority change is permitted
+ * @p: The task to affect
+ * @nice: The nice value to set
+ *
+ * Detemine if the requested task priority change is permitted for the
+ * specified task, returning 0 if permission is granted, -ve if denied.
+ */
+int cap_task_setnice(struct task_struct *p, int nice)
+{
+ return cap_safe_nice(p);
+}
+
+/*
+ * 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 int cap_prctl_drop(unsigned long cap)
+{
+ 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 commit_creds(new);
+}
+
+/**
+ * cap_task_prctl - Implement process control functions for this security module
+ * @option: The process control function requested
+ * @arg2, @arg3, @arg4, @arg5: The argument data for this function
+ *
+ * Allow process control functions (sys_prctl()) to alter capabilities; may
+ * also deny access to other functions not otherwise implemented here.
+ *
+ * Returns 0 or +ve on success, -ENOSYS if this function is not implemented
+ * here, other -ve on error. If -ENOSYS is returned, sys_prctl() and other LSM
+ * modules will consider performing the function.
+ */
+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;
+
+ switch (option) {
+ case PR_CAPBSET_READ:
+ if (!cap_valid(arg2))
+ return -EINVAL;
+ return !!cap_raised(old->cap_bset, arg2);
+
+ case PR_CAPBSET_DROP:
+ return cap_prctl_drop(arg2);
+
+ /*
+ * 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 ((((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_ns, CAP_SETPCAP,
+ SECURITY_CAP_AUDIT) != 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")
+ */
+ )
+ /* cannot change a locked bit */
+ return -EPERM;
+
+ new = prepare_creds();
+ if (!new)
+ return -ENOMEM;
+ new->securebits = arg2;
+ return commit_creds(new);
+
+ case PR_GET_SECUREBITS:
+ return old->securebits;
+
+ case PR_GET_KEEPCAPS:
+ return !!issecure(SECURE_KEEP_CAPS);
+
+ case PR_SET_KEEPCAPS:
+ if (arg2 > 1) /* Note, we rely on arg2 being unsigned here */
+ return -EINVAL;
+ if (issecure(SECURE_KEEP_CAPS_LOCKED))
+ 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);
+ 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) ||
+ issecure(SECURE_NO_CAP_AMBIENT_RAISE)))
+ 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 */
+ return -ENOSYS;
+ }
+}
+
+/**
+ * cap_vm_enough_memory - Determine whether a new virtual mapping is permitted
+ * @mm: The VM space in which the new mapping is to be made
+ * @pages: The size of the mapping
+ *
+ * Determine whether the allocation of a new virtual mapping by the current
+ * task is permitted, returning 1 if permission is granted, 0 if not.
+ */
+int cap_vm_enough_memory(struct mm_struct *mm, long pages)
+{
+ int cap_sys_admin = 0;
+
+ if (cap_capable(current_cred(), &init_user_ns, CAP_SYS_ADMIN,
+ SECURITY_CAP_NOAUDIT) == 0)
+ cap_sys_admin = 1;
+ return cap_sys_admin;
+}
+
+/*
+ * cap_mmap_addr - check if able to map given addr
+ * @addr: address attempting to be mapped
+ *
+ * If the process is attempting to map memory below dac_mmap_min_addr they need
+ * CAP_SYS_RAWIO. The other parameters to this function are unused by the
+ * capability security module. Returns 0 if this mapping should be allowed
+ * -EPERM if not.
+ */
+int cap_mmap_addr(unsigned long addr)
+{
+ int ret = 0;
+
+ if (addr < dac_mmap_min_addr) {
+ ret = cap_capable(current_cred(), &init_user_ns, CAP_SYS_RAWIO,
+ SECURITY_CAP_AUDIT);
+ /* set PF_SUPERPRIV if it turns out we allow the low mmap */
+ if (ret == 0)
+ current->flags |= PF_SUPERPRIV;
+ }
+ return ret;
+}
+
+int cap_mmap_file(struct file *file, unsigned long reqprot,
+ unsigned long prot, unsigned long flags)
+{
+ return 0;
+}
+
+#ifdef CONFIG_SECURITY
+
+struct security_hook_list capability_hooks[] = {
+ LSM_HOOK_INIT(capable, cap_capable),
+ LSM_HOOK_INIT(settime, cap_settime),
+ LSM_HOOK_INIT(ptrace_access_check, cap_ptrace_access_check),
+ LSM_HOOK_INIT(ptrace_traceme, cap_ptrace_traceme),
+ LSM_HOOK_INIT(capget, cap_capget),
+ LSM_HOOK_INIT(capset, cap_capset),
+ LSM_HOOK_INIT(bprm_set_creds, cap_bprm_set_creds),
+ LSM_HOOK_INIT(bprm_secureexec, cap_bprm_secureexec),
+ LSM_HOOK_INIT(inode_need_killpriv, cap_inode_need_killpriv),
+ LSM_HOOK_INIT(inode_killpriv, cap_inode_killpriv),
+ LSM_HOOK_INIT(mmap_addr, cap_mmap_addr),
+ LSM_HOOK_INIT(mmap_file, cap_mmap_file),
+ LSM_HOOK_INIT(task_fix_setuid, cap_task_fix_setuid),
+ LSM_HOOK_INIT(task_prctl, cap_task_prctl),
+ LSM_HOOK_INIT(task_setscheduler, cap_task_setscheduler),
+ LSM_HOOK_INIT(task_setioprio, cap_task_setioprio),
+ LSM_HOOK_INIT(task_setnice, cap_task_setnice),
+ LSM_HOOK_INIT(vm_enough_memory, cap_vm_enough_memory),
+};
+
+void __init capability_add_hooks(void)
+{
+ security_add_hooks(capability_hooks, ARRAY_SIZE(capability_hooks));
+}
+
+#endif /* CONFIG_SECURITY */