security: Return xattr name from security_dentry_init_security()

Right now security_dentry_init_security() only supports single security
label and is used by SELinux only. There are two users of this hook,
namely ceph and nfs.

NFS does not care about xattr name. Ceph hardcodes the xattr name to
security.selinux (XATTR_NAME_SELINUX).

I am making changes to fuse/virtiofs to send security label to virtiofsd
and I need to send xattr name as well. I also hardcoded the name of
xattr to security.selinux.

Stephen Smalley suggested that it probably is a good idea to modify
security_dentry_init_security() to also return name of xattr so that
we can avoid this hardcoding in the callers.

This patch adds a new parameter "const char **xattr_name" to
security_dentry_init_security() and LSM puts the name of xattr
too if caller asked for it (xattr_name != NULL).

Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Reviewed-by: Jeff Layton <jlayton@kernel.org>
Reviewed-by: Christian Brauner <christian.brauner@ubuntu.com>
Acked-by: James Morris <jamorris@linux.microsoft.com>
[PM: fixed typos in the commit description]
Signed-off-by: Paul Moore <paul@paul-moore.com>

diff --git a/fs/ceph/xattr.c b/fs/ceph/xattr.c
index 159a1ff..fcf7dfd 100644 (file)
--- a/fs/ceph/xattr.c
+++ b/fs/ceph/xattr.c
@@ -1311,7 +1311,7 @@ int ceph_security_init_secctx(struct dentry *dentry, umode_t mode,
        int err;
 
        err = security_dentry_init_security(dentry, mode, &dentry->d_name,
-                                           &as_ctx->sec_ctx,
+                                           &name, &as_ctx->sec_ctx,
                                            &as_ctx->sec_ctxlen);
        if (err < 0) {
                WARN_ON_ONCE(err != -EOPNOTSUPP);
@@ -1335,7 +1335,6 @@ int ceph_security_init_secctx(struct dentry *dentry, umode_t mode,
         * It only supports single security module and only selinux has
         * dentry_init_security hook.
         */
-       name = XATTR_NAME_SELINUX;
        name_len = strlen(name);
        err = ceph_pagelist_reserve(pagelist,
                                    4 * 2 + name_len + as_ctx->sec_ctxlen);

diff --git a/fs/nfs/nfs4proc.c b/fs/nfs/nfs4proc.c
index e1214bb..459860a 100644 (file)
--- a/fs/nfs/nfs4proc.c
+++ b/fs/nfs/nfs4proc.c
@@ -127,7 +127,8 @@ nfs4_label_init_security(struct inode *dir, struct dentry *dentry,
                return NULL;
 
        err = security_dentry_init_security(dentry, sattr->ia_mode,
-                               &dentry->d_name, (void **)&label->label, &label->len);
+                               &dentry->d_name, NULL,
+                               (void **)&label->label, &label->len);
        if (err == 0)
                return label;
 

diff --git a/include/linux/lsm_hook_defs.h b/include/linux/lsm_hook_defs.h
index 4c7ed02..a9ac70a 100644 (file)
--- a/include/linux/lsm_hook_defs.h
+++ b/include/linux/lsm_hook_defs.h
@@ -83,7 +83,8 @@ LSM_HOOK(int, 0, sb_add_mnt_opt, const char *option, const char *val,
 LSM_HOOK(int, 0, move_mount, const struct path *from_path,
         const struct path *to_path)
 LSM_HOOK(int, 0, dentry_init_security, struct dentry *dentry,
-        int mode, const struct qstr *name, void **ctx, u32 *ctxlen)
+        int mode, const struct qstr *name, const char **xattr_name,
+        void **ctx, u32 *ctxlen)
 LSM_HOOK(int, 0, dentry_create_files_as, struct dentry *dentry, int mode,
         struct qstr *name, const struct cred *old, struct cred *new)
 

diff --git a/include/linux/lsm_hooks.h b/include/linux/lsm_hooks.h
index 528554e..0bada4d 100644 (file)
--- a/include/linux/lsm_hooks.h
+++ b/include/linux/lsm_hooks.h
@@ -196,6 +196,9 @@
  *     @dentry dentry to use in calculating the context.
  *     @mode mode used to determine resource type.
  *     @name name of the last path component used to create file
+ *     @xattr_name pointer to place the pointer to security xattr name.
+ *                 Caller does not have to free the resulting pointer. Its
+ *                 a pointer to static string.
  *     @ctx pointer to place the pointer to the resulting context in.
  *     @ctxlen point to place the length of the resulting context.
  * @dentry_create_files_as:

diff --git a/include/linux/security.h b/include/linux/security.h
index cc6d393..7e0ba63 100644 (file)
--- a/include/linux/security.h
+++ b/include/linux/security.h
@@ -317,8 +317,9 @@ int security_add_mnt_opt(const char *option, const char *val,
                                int len, void **mnt_opts);
 int security_move_mount(const struct path *from_path, const struct path *to_path);
 int security_dentry_init_security(struct dentry *dentry, int mode,
-                                       const struct qstr *name, void **ctx,
-                                       u32 *ctxlen);
+                                 const struct qstr *name,
+                                 const char **xattr_name, void **ctx,
+                                 u32 *ctxlen);
 int security_dentry_create_files_as(struct dentry *dentry, int mode,
                                        struct qstr *name,
                                        const struct cred *old,
@@ -739,6 +740,7 @@ static inline void security_inode_free(struct inode *inode)
 static inline int security_dentry_init_security(struct dentry *dentry,
                                                 int mode,
                                                 const struct qstr *name,
+                                                const char **xattr_name,
                                                 void **ctx,
                                                 u32 *ctxlen)
 {

diff --git a/security/security.c b/security/security.c
index d9d53c1..95e30fa 100644 (file)
--- a/security/security.c
+++ b/security/security.c
@@ -1052,11 +1052,12 @@ void security_inode_free(struct inode *inode)
 }
 
 int security_dentry_init_security(struct dentry *dentry, int mode,
-                                       const struct qstr *name, void **ctx,
-                                       u32 *ctxlen)
+                                 const struct qstr *name,
+                                 const char **xattr_name, void **ctx,
+                                 u32 *ctxlen)
 {
        return call_int_hook(dentry_init_security, -EOPNOTSUPP, dentry, mode,
-                               name, ctx, ctxlen);
+                               name, xattr_name, ctx, ctxlen);
 }
 EXPORT_SYMBOL(security_dentry_init_security);
 

diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c
index 6f08cd2..1af2fbc 100644 (file)
--- a/security/selinux/hooks.c
+++ b/security/selinux/hooks.c
@@ -2927,7 +2927,8 @@ static void selinux_inode_free_security(struct inode *inode)
 }
 
 static int selinux_dentry_init_security(struct dentry *dentry, int mode,
-                                       const struct qstr *name, void **ctx,
+                                       const struct qstr *name,
+                                       const char **xattr_name, void **ctx,
                                        u32 *ctxlen)
 {
        u32 newsid;
@@ -2940,6 +2941,9 @@ static int selinux_dentry_init_security(struct dentry *dentry, int mode,
        if (rc)
                return rc;
 
+       if (xattr_name)
+               *xattr_name = XATTR_NAME_SELINUX;
+
        return security_sid_to_context(&selinux_state, newsid, (char **)ctx,
                                       ctxlen);
 }