[PATCH 2/2] kernfs: implement "trusted.*" xattr support

Tejun Heo
2013-11-23T22:40:15Z

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>
---
fs/kernfs/dir.c | 12 ++++++---
fs/kernfs/inode.c | 63 +++++++++++++++++++++++++++++++++++++++------
fs/kernfs/kernfs-internal.h | 7 +++++
fs/kernfs/symlink.c | 3 +++
4 files changed, 74 insertions(+), 11 deletions(-)

diff --git a/fs/kernfs/dir.c b/fs/kernfs/dir.c
index f51e062..a441e3b 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 a1f8382..18ad431 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 f25b354..910e485 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 12569a7..adf2875 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,
--
1.8.4.2