kernfs: implement "trusted.*" xattr support

kernfs inherited "security.*" xattr support from sysfs.  This patch
extends xattr support to "trusted.*" using simple_xattr_*().  As
trusted xattrs are restricted to CAP_SYS_ADMIN, simple_xattr_*() which
uses kernel memory for storage shouldn't be problematic.

Note that the existing "security.*" support doesn't implement
get/remove/list and the this patch only implements those ops for
"trusted.*".  We probably want to extend those ops to include support
for "security.*".

This patch will allow using kernfs from cgroup which requires
"trusted.*" xattr support.

Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: David P. Quigley <dpquigl@tycho.nsa.gov>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

4 files changed, 74 insertions, 11 deletions

diff --git a/fs/kernfs/dir.c b/fs/kernfs/dir.c
index f51e0625e666..a441e3be8052 100644
--- a/fs/kernfs/dir.c
+++ b/fs/kernfs/dir.c
@@ -243,9 +243,12 @@ void kernfs_put(struct sysfs_dirent *sd)
                 kernfs_put(sd->s_symlink.target_sd);
         if (sysfs_type(sd) & SYSFS_COPY_NAME)
                 kfree(sd->s_name);
-        if (sd->s_iattr && sd->s_iattr->ia_secdata)
-                security_release_secctx(sd->s_iattr->ia_secdata,
-                                        sd->s_iattr->ia_secdata_len);
+        if (sd->s_iattr) {
+                if (sd->s_iattr->ia_secdata)
+                        security_release_secctx(sd->s_iattr->ia_secdata,
+                                                sd->s_iattr->ia_secdata_len);
+                simple_xattrs_free(&sd->s_iattr->xattrs);
+        }
         kfree(sd->s_iattr);
         ida_simple_remove(&root->ino_ida, sd->s_ino);
         kmem_cache_free(sysfs_dir_cachep, sd);
@@ -718,6 +721,9 @@ const struct inode_operations sysfs_dir_inode_operations = {
         .setattr        = sysfs_setattr,
         .getattr        = sysfs_getattr,
         .setxattr       = sysfs_setxattr,
+        .removexattr    = sysfs_removexattr,
+        .getxattr       = sysfs_getxattr,
+        .listxattr      = sysfs_listxattr,
 };
 
 static struct sysfs_dirent *sysfs_leftmost_descendant(struct sysfs_dirent *pos)
diff --git a/fs/kernfs/inode.c b/fs/kernfs/inode.c
index a1f83825afca..18ad431e8c2a 100644
--- a/fs/kernfs/inode.c
+++ b/fs/kernfs/inode.c
@@ -35,6 +35,9 @@ static const struct inode_operations sysfs_inode_operations = {
         .setattr        = sysfs_setattr,
         .getattr        = sysfs_getattr,
         .setxattr       = sysfs_setxattr,
+        .removexattr    = sysfs_removexattr,
+        .getxattr       = sysfs_getxattr,
+        .listxattr      = sysfs_listxattr,
 };
 
 void __init sysfs_inode_init(void)
@@ -61,6 +64,8 @@ static struct sysfs_inode_attrs *sysfs_inode_attrs(struct sysfs_dirent *sd)
         iattrs->ia_gid = GLOBAL_ROOT_GID;
         iattrs->ia_atime = iattrs->ia_mtime = iattrs->ia_ctime = CURRENT_TIME;
 
+        simple_xattrs_init(&sd->s_iattr->xattrs);
+
         return sd->s_iattr;
 }
 
@@ -162,23 +167,25 @@ int sysfs_setxattr(struct dentry *dentry, const char *name, const void *value,
                 size_t size, int flags)
 {
         struct sysfs_dirent *sd = dentry->d_fsdata;
+        struct sysfs_inode_attrs *attrs;
         void *secdata;
         int error;
         u32 secdata_len = 0;
 
-        if (!sd)
-                return -EINVAL;
+        attrs = sysfs_inode_attrs(sd);
+        if (!attrs)
+                return -ENOMEM;
 
         if (!strncmp(name, XATTR_SECURITY_PREFIX, XATTR_SECURITY_PREFIX_LEN)) {
                 const char *suffix = name + XATTR_SECURITY_PREFIX_LEN;
                 error = security_inode_setsecurity(dentry->d_inode, suffix,
                                                 value, size, flags);
                 if (error)
-                        goto out;
+                        return error;
                 error = security_inode_getsecctx(dentry->d_inode,
                                                 &secdata, &secdata_len);
                 if (error)
-                        goto out;
+                        return error;
 
                 mutex_lock(&sysfs_mutex);
                 error = sysfs_sd_setsecdata(sd, &secdata, &secdata_len);
@@ -186,10 +193,50 @@ int sysfs_setxattr(struct dentry *dentry, const char *name, const void *value,
 
                 if (secdata)
                         security_release_secctx(secdata, secdata_len);
-        } else
-                return -EINVAL;
-out:
-        return error;
+                return error;
+        } else if (!strncmp(name, XATTR_TRUSTED_PREFIX, XATTR_TRUSTED_PREFIX_LEN)) {
+                return simple_xattr_set(&attrs->xattrs, name, value, size,
+                                        flags);
+        }
+
+        return -EINVAL;
+}
+
+int sysfs_removexattr(struct dentry *dentry, const char *name)
+{
+        struct sysfs_dirent *sd = dentry->d_fsdata;
+        struct sysfs_inode_attrs *attrs;
+
+        attrs = sysfs_inode_attrs(sd);
+        if (!attrs)
+                return -ENOMEM;
+
+        return simple_xattr_remove(&attrs->xattrs, name);
+}
+
+ssize_t sysfs_getxattr(struct dentry *dentry, const char *name, void *buf,
+                       size_t size)
+{
+        struct sysfs_dirent *sd = dentry->d_fsdata;
+        struct sysfs_inode_attrs *attrs;
+
+        attrs = sysfs_inode_attrs(sd);
+        if (!attrs)
+                return -ENOMEM;
+
+        return simple_xattr_get(&attrs->xattrs, name, buf, size);
+}
+
+ssize_t sysfs_listxattr(struct dentry *dentry, char *buf, size_t size)
+{
+        struct sysfs_dirent *sd = dentry->d_fsdata;
+        struct sysfs_inode_attrs *attrs;
+
+        attrs = sysfs_inode_attrs(sd);
+        if (!attrs)
+                return -ENOMEM;
+
+        return simple_xattr_list(&attrs->xattrs, buf, size);
 }
 
 static inline void set_default_inode_attr(struct inode *inode, umode_t mode)
diff --git a/fs/kernfs/kernfs-internal.h b/fs/kernfs/kernfs-internal.h
index f25b3548bcca..910e485b7333 100644
--- a/fs/kernfs/kernfs-internal.h
+++ b/fs/kernfs/kernfs-internal.h
@@ -14,6 +14,7 @@
 #include <linux/lockdep.h>
 #include <linux/fs.h>
 #include <linux/mutex.h>
+#include <linux/xattr.h>
 
 #include <linux/kernfs.h>
 
@@ -21,6 +22,8 @@ struct sysfs_inode_attrs {
         struct iattr            ia_iattr;
         void                    *ia_secdata;
         u32                     ia_secdata_len;
+
+        struct simple_xattrs    xattrs;
 };
 
 #define SD_DEACTIVATED_BIAS             INT_MIN
@@ -81,6 +84,10 @@ int sysfs_getattr(struct vfsmount *mnt, struct dentry *dentry,
                   struct kstat *stat);
 int sysfs_setxattr(struct dentry *dentry, const char *name, const void *value,
                    size_t size, int flags);
+int sysfs_removexattr(struct dentry *dentry, const char *name);
+ssize_t sysfs_getxattr(struct dentry *dentry, const char *name, void *buf,
+                       size_t size);
+ssize_t sysfs_listxattr(struct dentry *dentry, char *buf, size_t size);
 void sysfs_inode_init(void);
 
 /*
diff --git a/fs/kernfs/symlink.c b/fs/kernfs/symlink.c
index 12569a738837..adf28755b0ee 100644
--- a/fs/kernfs/symlink.c
+++ b/fs/kernfs/symlink.c
@@ -140,6 +140,9 @@ static void sysfs_put_link(struct dentry *dentry, struct nameidata *nd,
 
 const struct inode_operations sysfs_symlink_inode_operations = {
         .setxattr       = sysfs_setxattr,
+        .removexattr    = sysfs_removexattr,
+        .getxattr       = sysfs_getxattr,
+        .listxattr      = sysfs_listxattr,
         .readlink       = generic_readlink,
         .follow_link    = sysfs_follow_link,
         .put_link       = sysfs_put_link,