Re: [PATCH] Security/sysfs: Enable security xattrs to be set onsysfs files, directories, and symlinks.
From: David P. Quigley
Date: Wed Jul 15 2009 - 10:41:48 EST
Correcting a typo in Greg's email address (had susa instead of suse)
On Wed, 2009-07-15 at 09:48 -0400, David P. Quigley wrote:
> This patch adds a setxattr handler to the file, directory, and symlink
> inode_operations structures for sysfs. This handler uses two new LSM hooks. The
> first hook takes the xattr name and value and turns the context into a secid.
> The second hook allows for the secid to be taken from the sysfs_dirent and be
> pushed into the inode structure as the actual secid for the inode. As was
> suggested by Eric Biederman the struct iattr in the sysfs_dirent structure has
> been replaced by a structure which contains the iattr and secid to allow the
> changes to persist in the event that the inode representing the sysfs_dirent is
> evicted. Because sysfs only stores this information when a change is made all
> the optional data is moved into one dynamically allocated field.
>
> This patch addresses an issue where SELinux was denying virtd access to the PCI
> configuration entries in sysfs. The lack of setxattr handlers for sysfs
> required that a single label be assigned to all entries in sysfs. Granting virtd
> access to every entry in sysfs is not an acceptable solution so fine grained
> labeling of sysfs is required such that individual entries can be labeled
> appropriately.
>
> Signed-off-by: David P. Quigley <dpquigl@xxxxxxxxxxxxx>
> ---
> fs/sysfs/dir.c | 1 +
> fs/sysfs/inode.c | 112 ++++++++++++++++++++++++++++++--------------
> fs/sysfs/symlink.c | 2 +
> fs/sysfs/sysfs.h | 11 ++++-
> include/linux/security.h | 16 ++++++
> security/capability.c | 12 +++++
> security/security.c | 11 ++++
> security/selinux/hooks.c | 24 +++++++++
> security/smack/smack_lsm.c | 42 ++++++++++++++++-
> 9 files changed, 193 insertions(+), 38 deletions(-)
>
> diff --git a/fs/sysfs/dir.c b/fs/sysfs/dir.c
> index d88d0fa..fc21682 100644
> --- a/fs/sysfs/dir.c
> +++ b/fs/sysfs/dir.c
> @@ -760,6 +760,7 @@ static struct dentry * sysfs_lookup(struct inode *dir, struct dentry *dentry,
> const struct inode_operations sysfs_dir_inode_operations = {
> .lookup = sysfs_lookup,
> .setattr = sysfs_setattr,
> + .setxattr = sysfs_setxattr,
> };
>
> static void remove_dir(struct sysfs_dirent *sd)
> diff --git a/fs/sysfs/inode.c b/fs/sysfs/inode.c
> index 555f0ff..9bb1ce7 100644
> --- a/fs/sysfs/inode.c
> +++ b/fs/sysfs/inode.c
> @@ -18,6 +18,7 @@
> #include <linux/capability.h>
> #include <linux/errno.h>
> #include <linux/sched.h>
> +#include <linux/security.h>
> #include "sysfs.h"
>
> extern struct super_block * sysfs_sb;
> @@ -35,6 +36,7 @@ static struct backing_dev_info sysfs_backing_dev_info = {
>
> static const struct inode_operations sysfs_inode_operations ={
> .setattr = sysfs_setattr,
> + .setxattr = sysfs_setxattr,
> };
>
> int __init sysfs_inode_init(void)
> @@ -42,18 +44,37 @@ int __init sysfs_inode_init(void)
> return bdi_init(&sysfs_backing_dev_info);
> }
>
> +struct sysfs_inode_attrs * sysfs_init_inode_attrs(struct sysfs_dirent * sd)
> +{
> + struct sysfs_inode_attrs * attrs;
> + struct iattr * iattrs;
> +
> + attrs = kzalloc(sizeof(struct sysfs_inode_attrs), GFP_KERNEL);
> + if(!attrs)
> + return NULL;
> + iattrs = &attrs->ia_iattr;
> +
> + /* assign default attributes */
> + iattrs->ia_mode = sd->s_mode;
> + iattrs->ia_uid = 0;
> + iattrs->ia_gid = 0;
> + iattrs->ia_atime = iattrs->ia_mtime = iattrs->ia_ctime = CURRENT_TIME;
> +
> + return attrs;
> +}
> int sysfs_setattr(struct dentry * dentry, struct iattr * iattr)
> {
> struct inode * inode = dentry->d_inode;
> struct sysfs_dirent * sd = dentry->d_fsdata;
> - struct iattr * sd_iattr;
> + struct sysfs_inode_attrs * sd_attrs;
> + struct iattr * iattrs;
> unsigned int ia_valid = iattr->ia_valid;
> int error;
>
> if (!sd)
> return -EINVAL;
>
> - sd_iattr = sd->s_iattr;
> + sd_attrs = sd->s_iattr;
>
> error = inode_change_ok(inode, iattr);
> if (error)
> @@ -65,41 +86,57 @@ int sysfs_setattr(struct dentry * dentry, struct iattr * iattr)
> if (error)
> return error;
>
> - if (!sd_iattr) {
> + if (!sd_attrs) {
> /* setting attributes for the first time, allocate now */
> - sd_iattr = kzalloc(sizeof(struct iattr), GFP_KERNEL);
> - if (!sd_iattr)
> + sd_attrs = sysfs_init_inode_attrs(sd);
> + if (!sd_attrs)
> return -ENOMEM;
> - /* assign default attributes */
> - sd_iattr->ia_mode = sd->s_mode;
> - sd_iattr->ia_uid = 0;
> - sd_iattr->ia_gid = 0;
> - sd_iattr->ia_atime = sd_iattr->ia_mtime = sd_iattr->ia_ctime = CURRENT_TIME;
> - sd->s_iattr = sd_iattr;
> + sd->s_iattr = sd_attrs;
> + } else {
> + /* attributes were changed atleast once in past */
> + iattrs = &sd_attrs->ia_iattr;
> +
> + if (ia_valid & ATTR_UID)
> + iattrs->ia_uid = iattr->ia_uid;
> + if (ia_valid & ATTR_GID)
> + iattrs->ia_gid = iattr->ia_gid;
> + if (ia_valid & ATTR_ATIME)
> + iattrs->ia_atime = timespec_trunc(iattr->ia_atime,
> + inode->i_sb->s_time_gran);
> + if (ia_valid & ATTR_MTIME)
> + iattrs->ia_mtime = timespec_trunc(iattr->ia_mtime,
> + inode->i_sb->s_time_gran);
> + if (ia_valid & ATTR_CTIME)
> + iattrs->ia_ctime = timespec_trunc(iattr->ia_ctime,
> + inode->i_sb->s_time_gran);
> + if (ia_valid & ATTR_MODE) {
> + umode_t mode = iattr->ia_mode;
> +
> + if (!in_group_p(inode->i_gid) && !capable(CAP_FSETID))
> + mode &= ~S_ISGID;
> + iattrs->ia_mode = sd->s_mode = mode;
> + }
> }
> + return error;
> +}
>
> - /* attributes were changed atleast once in past */
> -
> - if (ia_valid & ATTR_UID)
> - sd_iattr->ia_uid = iattr->ia_uid;
> - if (ia_valid & ATTR_GID)
> - sd_iattr->ia_gid = iattr->ia_gid;
> - if (ia_valid & ATTR_ATIME)
> - sd_iattr->ia_atime = timespec_trunc(iattr->ia_atime,
> - inode->i_sb->s_time_gran);
> - if (ia_valid & ATTR_MTIME)
> - sd_iattr->ia_mtime = timespec_trunc(iattr->ia_mtime,
> - inode->i_sb->s_time_gran);
> - if (ia_valid & ATTR_CTIME)
> - sd_iattr->ia_ctime = timespec_trunc(iattr->ia_ctime,
> - inode->i_sb->s_time_gran);
> - if (ia_valid & ATTR_MODE) {
> - umode_t mode = iattr->ia_mode;
> -
> - if (!in_group_p(inode->i_gid) && !capable(CAP_FSETID))
> - mode &= ~S_ISGID;
> - sd_iattr->ia_mode = sd->s_mode = mode;
> - }
> +int sysfs_setxattr(struct dentry *dentry, const char *name, const void *value,
> + size_t size, int flags)
> +{
> + struct sysfs_dirent *sd = dentry->d_fsdata;
> +
> + int error;
> + u32 secid;
> +
> + if (!sd)
> + return -EINVAL;
> + if (!sd->s_iattr)
> + sd->s_iattr = sysfs_init_inode_attrs(sd);
> + if (!sd->s_iattr)
> + return -ENOMEM;
> + error = security_xattr_to_secid(name, value, size, &secid);
> + if (!error)
> + sd->s_iattr->ia_secid = secid;
>
> return error;
> }
> @@ -146,6 +183,7 @@ static int sysfs_count_nlink(struct sysfs_dirent *sd)
> static void sysfs_init_inode(struct sysfs_dirent *sd, struct inode *inode)
> {
> struct bin_attribute *bin_attr;
> + struct sysfs_inode_attrs * iattrs;
>
> inode->i_private = sysfs_get(sd);
> inode->i_mapping->a_ops = &sysfs_aops;
> @@ -154,16 +192,18 @@ static void sysfs_init_inode(struct sysfs_dirent *sd, struct inode *inode)
> inode->i_ino = sd->s_ino;
> lockdep_set_class(&inode->i_mutex, &sysfs_inode_imutex_key);
>
> - if (sd->s_iattr) {
> + iattrs = sd->s_iattr;
> + if (iattrs) {
> /* sysfs_dirent has non-default attributes
> * get them for the new inode from persistent copy
> * in sysfs_dirent
> */
> - set_inode_attr(inode, sd->s_iattr);
> + set_inode_attr(inode, &iattrs->ia_iattr);
> + if (iattrs->ia_secid)
> + security_inode_setsecid(inode, iattrs->ia_secid);
> } else
> set_default_inode_attr(inode, sd->s_mode);
>
> -
> /* initialize inode according to type */
> switch (sysfs_type(sd)) {
> case SYSFS_DIR:
> diff --git a/fs/sysfs/symlink.c b/fs/sysfs/symlink.c
> index 1d897ad..c5081ad 100644
> --- a/fs/sysfs/symlink.c
> +++ b/fs/sysfs/symlink.c
> @@ -16,6 +16,7 @@
> #include <linux/kobject.h>
> #include <linux/namei.h>
> #include <linux/mutex.h>
> +#include <linux/security.h>
>
> #include "sysfs.h"
>
> @@ -209,6 +210,7 @@ static void sysfs_put_link(struct dentry *dentry, struct nameidata *nd, void *co
> }
>
> const struct inode_operations sysfs_symlink_inode_operations = {
> + .setxattr = sysfs_setxattr,
> .readlink = generic_readlink,
> .follow_link = sysfs_follow_link,
> .put_link = sysfs_put_link,
> diff --git a/fs/sysfs/sysfs.h b/fs/sysfs/sysfs.h
> index 3fa0d98..f59a211 100644
> --- a/fs/sysfs/sysfs.h
> +++ b/fs/sysfs/sysfs.h
> @@ -8,6 +8,8 @@
> * This file is released under the GPLv2.
> */
>
> +#include <linux/fs.h>
> +
> struct sysfs_open_dirent;
>
> /* type-specific structures for sysfs_dirent->s_* union members */
> @@ -31,6 +33,11 @@ struct sysfs_elem_bin_attr {
> struct hlist_head buffers;
> };
>
> +struct sysfs_inode_attrs {
> + struct iattr ia_iattr;
> + u32 ia_secid;
> +};
> +
> /*
> * sysfs_dirent - the building block of sysfs hierarchy. Each and
> * every sysfs node is represented by single sysfs_dirent.
> @@ -56,7 +63,7 @@ struct sysfs_dirent {
> unsigned int s_flags;
> ino_t s_ino;
> umode_t s_mode;
> - struct iattr *s_iattr;
> + struct sysfs_inode_attrs *s_iattr;
> };
>
> #define SD_DEACTIVATED_BIAS INT_MIN
> @@ -148,6 +155,8 @@ static inline void __sysfs_put(struct sysfs_dirent *sd)
> struct inode *sysfs_get_inode(struct sysfs_dirent *sd);
> void sysfs_delete_inode(struct inode *inode);
> int sysfs_setattr(struct dentry *dentry, struct iattr *iattr);
> +int sysfs_setxattr(struct dentry *dentry, const char *name, const void *value,
> + size_t size, int flags);
> int sysfs_hash_and_remove(struct sysfs_dirent *dir_sd, const char *name);
> int sysfs_inode_init(void);
>
> diff --git a/include/linux/security.h b/include/linux/security.h
> index 1459091..35ecc8d 100644
> --- a/include/linux/security.h
> +++ b/include/linux/security.h
> @@ -1440,6 +1440,9 @@ struct security_operations {
> int (*inode_setsecurity) (struct inode *inode, const char *name, const void *value, size_t size, int flags);
> int (*inode_listsecurity) (struct inode *inode, char *buffer, size_t buffer_size);
> void (*inode_getsecid) (const struct inode *inode, u32 *secid);
> + void (*inode_setsecid)(struct inode *inode, u32 secid);
> + int (*xattr_to_secid) (const char *name, const void *value,
> + size_t size, u32 *secid);
>
> int (*file_permission) (struct file *file, int mask);
> int (*file_alloc_security) (struct file *file);
> @@ -1699,6 +1702,9 @@ int security_inode_getsecurity(const struct inode *inode, const char *name, void
> int security_inode_setsecurity(struct inode *inode, const char *name, const void *value, size_t size, int flags);
> int security_inode_listsecurity(struct inode *inode, char *buffer, size_t buffer_size);
> void security_inode_getsecid(const struct inode *inode, u32 *secid);
> +void security_inode_setsecid(struct inode *inode, u32 secid);
> +int security_xattr_to_secid(const char *name, const void *value,
> + size_t size, u32 *secid);
> int security_file_permission(struct file *file, int mask);
> int security_file_alloc(struct file *file);
> void security_file_free(struct file *file);
> @@ -2172,6 +2178,16 @@ static inline void security_inode_getsecid(const struct inode *inode, u32 *secid
> *secid = 0;
> }
>
> +static inline void security_inode_setsecid(struct inode *inode, u32 secid)
> +{
> +}
> +
> +static inline int security_xattr_to_secid(const char *name, const void *value,
> + size_t size, u32 *secid)
> +{
> + return -EOPNOTSUPP;
> +}
> +
> static inline int security_file_permission(struct file *file, int mask)
> {
> return 0;
> diff --git a/security/capability.c b/security/capability.c
> index f218dd3..a3f3d5b 100644
> --- a/security/capability.c
> +++ b/security/capability.c
> @@ -263,6 +263,16 @@ static void cap_inode_getsecid(const struct inode *inode, u32 *secid)
> *secid = 0;
> }
>
> +static void cap_inode_setsecid(struct inode *inode, u32 secid)
> +{
> +}
> +
> +int cap_xattr_to_secid(const char *name, const void *value,
> + size_t size, u32 *secid)
> +{
> + return -EOPNOTSUPP;
> +}
> +
> #ifdef CONFIG_SECURITY_PATH
> static int cap_path_mknod(struct path *dir, struct dentry *dentry, int mode,
> unsigned int dev)
> @@ -926,6 +936,8 @@ void security_fixup_ops(struct security_operations *ops)
> set_to_cap_if_null(ops, inode_setsecurity);
> set_to_cap_if_null(ops, inode_listsecurity);
> set_to_cap_if_null(ops, inode_getsecid);
> + set_to_cap_if_null(ops, inode_setsecid);
> + set_to_cap_if_null(ops, xattr_to_secid);
> #ifdef CONFIG_SECURITY_PATH
> set_to_cap_if_null(ops, path_mknod);
> set_to_cap_if_null(ops, path_mkdir);
> diff --git a/security/security.c b/security/security.c
> index 4501c5e..8313e15 100644
> --- a/security/security.c
> +++ b/security/security.c
> @@ -615,6 +615,17 @@ void security_inode_getsecid(const struct inode *inode, u32 *secid)
> security_ops->inode_getsecid(inode, secid);
> }
>
> +void security_inode_setsecid(struct inode *inode, u32 secid)
> +{
> + security_ops->inode_setsecid(inode, secid);
> +}
> +
> +int security_xattr_to_secid(const char *name, const void *value,
> + size_t size, u32 *secid)
> +{
> + return security_ops->xattr_to_secid(name, value, size, secid);
> +}
> +
> int security_file_permission(struct file *file, int mask)
> {
> return security_ops->file_permission(file, mask);
> diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c
> index 2081055..395c36d 100644
> --- a/security/selinux/hooks.c
> +++ b/security/selinux/hooks.c
> @@ -448,6 +448,10 @@ static int sb_finish_set_opts(struct super_block *sb)
> sbsec->behavior > ARRAY_SIZE(labeling_behaviors))
> sbsec->flags &= ~SE_SBLABELSUPP;
>
> + /* Special handling for sysfs. Is genfs but also has setxattr handler*/
> + if (strncmp(sb->s_type->name, "sysfs", sizeof("sysfs")) == 0)
> + sbsec->flags |= SE_SBLABELSUPP;
> +
> /* Initialize the root inode. */
> rc = inode_doinit_with_dentry(root_inode, root);
>
> @@ -2931,6 +2935,24 @@ static void selinux_inode_getsecid(const struct inode *inode, u32 *secid)
> *secid = isec->sid;
> }
>
> +static void selinux_inode_setsecid(struct inode *inode, u32 secid)
> +{
> + struct inode_security_struct *isec = inode->i_security;
> + isec->sid = secid;
> +}
> +
> +static int selinux_xattr_to_secid(const char *name, const void *value,
> + size_t size, u32 *secid)
> +{
> + if (strcmp(name, XATTR_NAME_SELINUX))
> + return -EOPNOTSUPP;
> +
> + if (!value || !size)
> + return -EINVAL;
> +
> + return security_context_to_sid((void *)value, size, secid);
> +}
> +
> /* file security operations */
>
> static int selinux_revalidate_file_permission(struct file *file, int mask)
> @@ -5372,6 +5394,8 @@ static struct security_operations selinux_ops = {
> .inode_setsecurity = selinux_inode_setsecurity,
> .inode_listsecurity = selinux_inode_listsecurity,
> .inode_getsecid = selinux_inode_getsecid,
> + .inode_setsecid = selinux_inode_setsecid,
> + .xattr_to_secid = selinux_xattr_to_secid,
>
> .file_permission = selinux_file_permission,
> .file_alloc_security = selinux_file_alloc_security,
> diff --git a/security/smack/smack_lsm.c b/security/smack/smack_lsm.c
> index 1c9bdbc..be66c8e 100644
> --- a/security/smack/smack_lsm.c
> +++ b/security/smack/smack_lsm.c
> @@ -869,6 +869,44 @@ static void smack_inode_getsecid(const struct inode *inode, u32 *secid)
> *secid = smack_to_secid(isp->smk_inode);
> }
>
> +/**
> + * smack_inode_setsecid - Set inode's security id
> + * @inode: inode to set the info in
> + * @secid: secid to set the inode to
> + */
> +static void smack_inode_setsecid(struct inode *inode, u32 secid)
> +{
> + struct inode_smack *isp = inode->i_security;
> +
> + isp->smk_inode = smack_from_secid(secid);
> +}
> +
> +/**
> + * smack_xattr_to_secid - convert a valid xattr into a secid
> + * @name: name of the xattr attempting to be converted
> + * @value: value associated with the xattr
> + * @size: size of value
> + * @secid: location to place resuting secid
> + */
> +static int smack_xattr_to_secid(const char *name, const void* value,
> + size_t size, u32 *secid)
> +{
> + char *sp;
> +
> + if (strcmp(name, XATTR_NAME_SMACK))
> + return -EOPNOTSUPP;
> +
> + if (!value || !size)
> + return -EINVAL;
> +
> + sp = smk_import(value, size);
> + if (sp == NULL)
> + return -EINVAL;
> +
> + *secid = smack_to_secid(sp);
> +}
> +
> +
> /*
> * File Hooks
> */
> @@ -3062,7 +3100,9 @@ struct security_operations smack_ops = {
> .inode_setsecurity = smack_inode_setsecurity,
> .inode_listsecurity = smack_inode_listsecurity,
> .inode_getsecid = smack_inode_getsecid,
> -
> + .inode_setsecid = smack_inode_setsecid,
> + .xattr_to_secid = smack_xattr_to_secid,
> +
> .file_permission = smack_file_permission,
> .file_alloc_security = smack_file_alloc_security,
> .file_free_security = smack_file_free_security,
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/