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-rw-r--r--security/commoncap.c277
1 files changed, 256 insertions, 21 deletions
diff --git a/security/commoncap.c b/security/commoncap.c
index d8e26fb9781d..6bf72b175b49 100644
--- a/security/commoncap.c
+++ b/security/commoncap.c
@@ -82,8 +82,11 @@ int cap_capable(const struct cred *cred, struct user_namespace *targ_ns,
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)
+ /*
+ * If we're already at a lower level than we're looking for,
+ * we're done searching.
+ */
+ if (ns->level <= cred->user_ns->level)
return -EPERM;
/*
@@ -323,6 +326,209 @@ int cap_inode_killpriv(struct dentry *dentry)
return error;
}
+static bool rootid_owns_currentns(kuid_t kroot)
+{
+ struct user_namespace *ns;
+
+ if (!uid_valid(kroot))
+ return false;
+
+ for (ns = current_user_ns(); ; ns = ns->parent) {
+ if (from_kuid(ns, kroot) == 0)
+ return true;
+ if (ns == &init_user_ns)
+ break;
+ }
+
+ return false;
+}
+
+static __u32 sansflags(__u32 m)
+{
+ return m & ~VFS_CAP_FLAGS_EFFECTIVE;
+}
+
+static bool is_v2header(size_t size, __le32 magic)
+{
+ __u32 m = le32_to_cpu(magic);
+ if (size != XATTR_CAPS_SZ_2)
+ return false;
+ return sansflags(m) == VFS_CAP_REVISION_2;
+}
+
+static bool is_v3header(size_t size, __le32 magic)
+{
+ __u32 m = le32_to_cpu(magic);
+
+ if (size != XATTR_CAPS_SZ_3)
+ return false;
+ return sansflags(m) == VFS_CAP_REVISION_3;
+}
+
+/*
+ * getsecurity: We are called for security.* before any attempt to read the
+ * xattr from the inode itself.
+ *
+ * This gives us a chance to read the on-disk value and convert it. If we
+ * return -EOPNOTSUPP, then vfs_getxattr() will call the i_op handler.
+ *
+ * Note we are not called by vfs_getxattr_alloc(), but that is only called
+ * by the integrity subsystem, which really wants the unconverted values -
+ * so that's good.
+ */
+int cap_inode_getsecurity(struct inode *inode, const char *name, void **buffer,
+ bool alloc)
+{
+ int size, ret;
+ kuid_t kroot;
+ uid_t root, mappedroot;
+ char *tmpbuf = NULL;
+ struct vfs_cap_data *cap;
+ struct vfs_ns_cap_data *nscap;
+ struct dentry *dentry;
+ struct user_namespace *fs_ns;
+
+ if (strcmp(name, "capability") != 0)
+ return -EOPNOTSUPP;
+
+ dentry = d_find_alias(inode);
+ if (!dentry)
+ return -EINVAL;
+
+ size = sizeof(struct vfs_ns_cap_data);
+ ret = (int) vfs_getxattr_alloc(dentry, XATTR_NAME_CAPS,
+ &tmpbuf, size, GFP_NOFS);
+ dput(dentry);
+
+ if (ret < 0)
+ return ret;
+
+ fs_ns = inode->i_sb->s_user_ns;
+ cap = (struct vfs_cap_data *) tmpbuf;
+ if (is_v2header((size_t) ret, cap->magic_etc)) {
+ /* If this is sizeof(vfs_cap_data) then we're ok with the
+ * on-disk value, so return that. */
+ if (alloc)
+ *buffer = tmpbuf;
+ else
+ kfree(tmpbuf);
+ return ret;
+ } else if (!is_v3header((size_t) ret, cap->magic_etc)) {
+ kfree(tmpbuf);
+ return -EINVAL;
+ }
+
+ nscap = (struct vfs_ns_cap_data *) tmpbuf;
+ root = le32_to_cpu(nscap->rootid);
+ kroot = make_kuid(fs_ns, root);
+
+ /* If the root kuid maps to a valid uid in current ns, then return
+ * this as a nscap. */
+ mappedroot = from_kuid(current_user_ns(), kroot);
+ if (mappedroot != (uid_t)-1 && mappedroot != (uid_t)0) {
+ if (alloc) {
+ *buffer = tmpbuf;
+ nscap->rootid = cpu_to_le32(mappedroot);
+ } else
+ kfree(tmpbuf);
+ return size;
+ }
+
+ if (!rootid_owns_currentns(kroot)) {
+ kfree(tmpbuf);
+ return -EOPNOTSUPP;
+ }
+
+ /* This comes from a parent namespace. Return as a v2 capability */
+ size = sizeof(struct vfs_cap_data);
+ if (alloc) {
+ *buffer = kmalloc(size, GFP_ATOMIC);
+ if (*buffer) {
+ struct vfs_cap_data *cap = *buffer;
+ __le32 nsmagic, magic;
+ magic = VFS_CAP_REVISION_2;
+ nsmagic = le32_to_cpu(nscap->magic_etc);
+ if (nsmagic & VFS_CAP_FLAGS_EFFECTIVE)
+ magic |= VFS_CAP_FLAGS_EFFECTIVE;
+ memcpy(&cap->data, &nscap->data, sizeof(__le32) * 2 * VFS_CAP_U32);
+ cap->magic_etc = cpu_to_le32(magic);
+ }
+ }
+ kfree(tmpbuf);
+ return size;
+}
+
+static kuid_t rootid_from_xattr(const void *value, size_t size,
+ struct user_namespace *task_ns)
+{
+ const struct vfs_ns_cap_data *nscap = value;
+ uid_t rootid = 0;
+
+ if (size == XATTR_CAPS_SZ_3)
+ rootid = le32_to_cpu(nscap->rootid);
+
+ return make_kuid(task_ns, rootid);
+}
+
+static bool validheader(size_t size, __le32 magic)
+{
+ return is_v2header(size, magic) || is_v3header(size, magic);
+}
+
+/*
+ * User requested a write of security.capability. If needed, update the
+ * xattr to change from v2 to v3, or to fixup the v3 rootid.
+ *
+ * If all is ok, we return the new size, on error return < 0.
+ */
+int cap_convert_nscap(struct dentry *dentry, void **ivalue, size_t size)
+{
+ struct vfs_ns_cap_data *nscap;
+ uid_t nsrootid;
+ const struct vfs_cap_data *cap = *ivalue;
+ __u32 magic, nsmagic;
+ struct inode *inode = d_backing_inode(dentry);
+ struct user_namespace *task_ns = current_user_ns(),
+ *fs_ns = inode->i_sb->s_user_ns;
+ kuid_t rootid;
+ size_t newsize;
+
+ if (!*ivalue)
+ return -EINVAL;
+ if (!validheader(size, cap->magic_etc))
+ return -EINVAL;
+ if (!capable_wrt_inode_uidgid(inode, CAP_SETFCAP))
+ return -EPERM;
+ if (size == XATTR_CAPS_SZ_2)
+ if (ns_capable(inode->i_sb->s_user_ns, CAP_SETFCAP))
+ /* user is privileged, just write the v2 */
+ return size;
+
+ rootid = rootid_from_xattr(*ivalue, size, task_ns);
+ if (!uid_valid(rootid))
+ return -EINVAL;
+
+ nsrootid = from_kuid(fs_ns, rootid);
+ if (nsrootid == -1)
+ return -EINVAL;
+
+ newsize = sizeof(struct vfs_ns_cap_data);
+ nscap = kmalloc(newsize, GFP_ATOMIC);
+ if (!nscap)
+ return -ENOMEM;
+ nscap->rootid = cpu_to_le32(nsrootid);
+ nsmagic = VFS_CAP_REVISION_3;
+ magic = le32_to_cpu(cap->magic_etc);
+ if (magic & VFS_CAP_FLAGS_EFFECTIVE)
+ nsmagic |= VFS_CAP_FLAGS_EFFECTIVE;
+ nscap->magic_etc = cpu_to_le32(nsmagic);
+ memcpy(&nscap->data, &cap->data, sizeof(__le32) * 2 * VFS_CAP_U32);
+
+ kvfree(*ivalue);
+ *ivalue = nscap;
+ return newsize;
+}
+
/*
* Calculate the new process capability sets from the capability sets attached
* to a file.
@@ -376,7 +582,10 @@ int get_vfs_caps_from_disk(const struct dentry *dentry, struct cpu_vfs_cap_data
__u32 magic_etc;
unsigned tocopy, i;
int size;
- struct vfs_cap_data caps;
+ struct vfs_ns_cap_data data, *nscaps = &data;
+ struct vfs_cap_data *caps = (struct vfs_cap_data *) &data;
+ kuid_t rootkuid;
+ struct user_namespace *fs_ns = inode->i_sb->s_user_ns;
memset(cpu_caps, 0, sizeof(struct cpu_vfs_cap_data));
@@ -384,18 +593,20 @@ int get_vfs_caps_from_disk(const struct dentry *dentry, struct cpu_vfs_cap_data
return -ENODATA;
size = __vfs_getxattr((struct dentry *)dentry, inode,
- XATTR_NAME_CAPS, &caps, XATTR_CAPS_SZ);
+ XATTR_NAME_CAPS, &data, 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);
+ cpu_caps->magic_etc = magic_etc = le32_to_cpu(caps->magic_etc);
+ rootkuid = make_kuid(fs_ns, 0);
switch (magic_etc & VFS_CAP_REVISION_MASK) {
case VFS_CAP_REVISION_1:
if (size != XATTR_CAPS_SZ_1)
@@ -407,15 +618,27 @@ int get_vfs_caps_from_disk(const struct dentry *dentry, struct cpu_vfs_cap_data
return -EINVAL;
tocopy = VFS_CAP_U32_2;
break;
+ case VFS_CAP_REVISION_3:
+ if (size != XATTR_CAPS_SZ_3)
+ return -EINVAL;
+ tocopy = VFS_CAP_U32_3;
+ rootkuid = make_kuid(fs_ns, le32_to_cpu(nscaps->rootid));
+ break;
+
default:
return -EINVAL;
}
+ /* Limit the caps to the mounter of the filesystem
+ * or the more limited uid specified in the xattr.
+ */
+ if (!rootid_owns_currentns(rootkuid))
+ return -ENODATA;
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[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;
@@ -453,8 +676,8 @@ static int get_file_caps(struct linux_binprm *bprm, bool *effective, bool *has_c
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);
+ printk(KERN_NOTICE "Invalid argument reading file caps for %s\n",
+ bprm->filename);
else if (rc == -ENODATA)
rc = 0;
goto out;
@@ -633,15 +856,19 @@ skip:
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;
+ /* Ignore non-security xattrs */
+ if (strncmp(name, XATTR_SECURITY_PREFIX,
+ sizeof(XATTR_SECURITY_PREFIX) - 1) != 0)
+ return 0;
+
+ /*
+ * For XATTR_NAME_CAPS the check will be done in
+ * cap_convert_nscap(), called by setxattr()
+ */
+ if (strcmp(name, XATTR_NAME_CAPS) == 0)
return 0;
- }
- if (!strncmp(name, XATTR_SECURITY_PREFIX,
- sizeof(XATTR_SECURITY_PREFIX) - 1) &&
- !capable(CAP_SYS_ADMIN))
+ if (!capable(CAP_SYS_ADMIN))
return -EPERM;
return 0;
}
@@ -659,15 +886,22 @@ int cap_inode_setxattr(struct dentry *dentry, const char *name,
*/
int cap_inode_removexattr(struct dentry *dentry, const char *name)
{
- if (!strcmp(name, XATTR_NAME_CAPS)) {
- if (!capable(CAP_SETFCAP))
+ /* Ignore non-security xattrs */
+ if (strncmp(name, XATTR_SECURITY_PREFIX,
+ sizeof(XATTR_SECURITY_PREFIX) - 1) != 0)
+ return 0;
+
+ if (strcmp(name, XATTR_NAME_CAPS) == 0) {
+ /* security.capability gets namespaced */
+ struct inode *inode = d_backing_inode(dentry);
+ if (!inode)
+ return -EINVAL;
+ if (!capable_wrt_inode_uidgid(inode, CAP_SETFCAP))
return -EPERM;
return 0;
}
- if (!strncmp(name, XATTR_SECURITY_PREFIX,
- sizeof(XATTR_SECURITY_PREFIX) - 1) &&
- !capable(CAP_SYS_ADMIN))
+ if (!capable(CAP_SYS_ADMIN))
return -EPERM;
return 0;
}
@@ -1054,6 +1288,7 @@ struct security_hook_list capability_hooks[] __lsm_ro_after_init = {
LSM_HOOK_INIT(bprm_set_creds, cap_bprm_set_creds),
LSM_HOOK_INIT(inode_need_killpriv, cap_inode_need_killpriv),
LSM_HOOK_INIT(inode_killpriv, cap_inode_killpriv),
+ LSM_HOOK_INIT(inode_getsecurity, cap_inode_getsecurity),
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),
generated by cgit v1.2.3 (git 2.39.1) at 2024-12-18 06:35:25 +0100