On 3/25/20 7:02 PM, Daniel Colascione wrote:
This change adds two new functions, anon_inode_getfile_secure and
anon_inode_getfd_secure, that create anonymous-node files with
individual non-S_PRIVATE inodes to which security modules can apply
policy. Existing callers continue using the original singleton-inode
kind of anonymous-inode file. We can transition anonymous inode users
to the new kind of anonymous inode in individual patches for the sake
of bisection and review.
The new functions accept an optional context_inode parameter that
callers can use to provide additional contextual information to
security modules, e.g., indicating that one anonymous struct file is a
logical child of another, allowing a security model to propagate
security information from one to the other.
Signed-off-by: Daniel Colascione <dancol@xxxxxxxxxx>
---
diff --git a/fs/anon_inodes.c b/fs/anon_inodes.c
index 89714308c25b..114a04fc1db4 100644
--- a/fs/anon_inodes.c
+++ b/fs/anon_inodes.c
@@ -55,75 +55,135 @@ static struct file_system_type anon_inode_fs_type = {
.kill_sb = kill_anon_super,
};
-/**
- * anon_inode_getfile - creates a new file instance by hooking it up to an
- * anonymous inode, and a dentry that describe the "class"
- * of the file
- *
- * @name: [in] name of the "class" of the new file
- * @fops: [in] file operations for the new file
- * @priv: [in] private data for the new file (will be file's private_data)
- * @flags: [in] flags
- *
- * Creates a new file by hooking it on a single inode. This is useful for files
- * that do not need to have a full-fledged inode in order to operate correctly.
- * All the files created with anon_inode_getfile() will share a single inode,
- * hence saving memory and avoiding code duplication for the file/inode/dentry
- * setup. Returns the newly created file* or an error pointer.
- */
-struct file *anon_inode_getfile(const char *name,
- const struct file_operations *fops,
- void *priv, int flags)
+static struct inode *anon_inode_make_secure_inode(
+ const char *name,
+ const struct inode *context_inode,
+ const struct file_operations *fops)
+{
+ struct inode *inode;
+ const struct qstr qname = QSTR_INIT(name, strlen(name));
+ int error;
+
+ inode = alloc_anon_inode(anon_inode_mnt->mnt_sb);
+ if (IS_ERR(inode))
+ return ERR_PTR(PTR_ERR(inode));
Just return inode here?
+ inode->i_flags &= ~S_PRIVATE;
+ error = security_inode_init_security_anon(
+ inode, &qname, fops, context_inode);
Would drop fops argument to the security hook until we have an actual
user of it; one can always add it later.
diff --git a/fs/userfaultfd.c b/fs/userfaultfd.c
index 37df7c9eedb1..07b0f6e03849 100644
--- a/fs/userfaultfd.c
+++ b/fs/userfaultfd.c
@@ -1014,8 +1014,6 @@ static __poll_t userfaultfd_poll(struct file *file, poll_table *wait)
}
}
-static const struct file_operations userfaultfd_fops;
-
static int resolve_userfault_fork(struct userfaultfd_ctx *ctx,
struct userfaultfd_ctx *new,
struct uffd_msg *msg)
@@ -1920,7 +1918,7 @@ static void userfaultfd_show_fdinfo(struct seq_file *m, struct file *f)
}
#endif
-static const struct file_operations userfaultfd_fops = {
+const struct file_operations userfaultfd_fops = {
#ifdef CONFIG_PROC_FS
.show_fdinfo = userfaultfd_show_fdinfo,
#endif
These changes can be dropped entirely AFAICT.
diff --git a/include/linux/lsm_hooks.h b/include/linux/lsm_hooks.h
index 20d8cf194fb7..de5d37e388df 100644
--- a/include/linux/lsm_hooks.h
+++ b/include/linux/lsm_hooks.h
@@ -215,6 +215,10 @@
* Returns 0 if @name and @value have been successfully set,
* -EOPNOTSUPP if no security attribute is needed, or
* -ENOMEM on memory allocation failure.
+ * @inode_init_security_anon:
+ * Set up a secure anonymous inode.
+ * Returns 0 on success. Returns -EPERM if the security module denies
+ * the creation of this inode.
I'd favor describing the arguments (@name, @context_inode) too.
* @inode_create:
* Check permission to create a regular file.
* @dir contains inode structure of the parent of the new file.
@@ -1552,6 +1556,10 @@ union security_list_options {
const struct qstr *qstr,
const char **name, void **value,
size_t *len);
+ int (*inode_init_security_anon)(struct inode *inode,
+ const struct qstr *name,
+ const struct file_operations *fops,
+ const struct inode *context_inode);
int (*inode_create)(struct inode *dir, struct dentry *dentry,
Can drop the fops argument.
diff --git a/include/linux/security.h b/include/linux/security.h
index 64b19f050343..8ea76af0be7a 100644
--- a/include/linux/security.h
+++ b/include/linux/security.h
@@ -320,6 +320,10 @@ void security_inode_free(struct inode *inode);
int security_inode_init_security(struct inode *inode, struct inode *dir,
const struct qstr *qstr,
initxattrs initxattrs, void *fs_data);
+int security_inode_init_security_anon(struct inode *inode,
+ const struct qstr *name,
+ const struct file_operations *fops,
+ const struct inode *context_inode);
Ditto
diff --git a/security/security.c b/security/security.c
index 565bc9b67276..d06f3969c030 100644
--- a/security/security.c
+++ b/security/security.c
@@ -1033,6 +1033,16 @@ int security_inode_init_security(struct inode *inode, struct inode *dir,
}
EXPORT_SYMBOL(security_inode_init_security);
+int
+security_inode_init_security_anon(struct inode *inode,
+ const struct qstr *name,
+ const struct file_operations *fops,
+ const struct inode *context_inode)
+{
+ return call_int_hook(inode_init_security_anon, 0, inode, name,
+ fops, context_inode);
+}
+
And again.
