[RFC PATCH v2 5/9] fs: add anon_inode_getfile_secure() similar to anon_inode_getfd_secure()

Paul Moore
2021-08-11T20:50:46Z

Extending the secure anonymous inode support to other subsystems
requires that we have a secure anon_inode_getfile() variant in
addition to the existing secure anon_inode_getfd() variant.

Thankfully we can reuse the existing __anon_inode_getfile() function
and just wrap it with the proper arguments.

Signed-off-by: Paul Moore <paul@paul-moore.com>

---
v2:
- no change
v1:
- initial draft
---
fs/anon_inodes.c | 29 +++++++++++++++++++++++++++++
include/linux/anon_inodes.h | 4 ++++
2 files changed, 33 insertions(+)

diff --git a/fs/anon_inodes.c b/fs/anon_inodes.c
index a280156138ed..e0c3e33c4177 100644
--- a/fs/anon_inodes.c
+++ b/fs/anon_inodes.c
@@ -148,6 +148,35 @@ struct file *anon_inode_getfile(const char *name,
}
EXPORT_SYMBOL_GPL(anon_inode_getfile);

+/**
+ * anon_inode_getfile_secure - Like anon_inode_getfile(), but creates a new
+ * !S_PRIVATE anon inode rather than reuse the
+ * singleton anon inode and calls the
+ * inode_init_security_anon() LSM hook. This
+ * allows for both the inode to have its own
+ * security context and for the LSM to enforce
+ * policy on the inode's creation.
+ *
+ * @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
+ * @context_inode:
+ * [in] the logical relationship with the new inode (optional)
+ *
+ * The LSM may use @context_inode in inode_init_security_anon(), but a
+ * reference to it is not held. Returns the newly created file* or an error
+ * pointer. See the anon_inode_getfile() documentation for more information.
+ */
+struct file *anon_inode_getfile_secure(const char *name,
+ const struct file_operations *fops,
+ void *priv, int flags,
+ const struct inode *context_inode)
+{
+ return __anon_inode_getfile(name, fops, priv, flags,
+ context_inode, true);
+}
+
static int __anon_inode_getfd(const char *name,
const struct file_operations *fops,
void *priv, int flags,
diff --git a/include/linux/anon_inodes.h b/include/linux/anon_inodes.h
index 71881a2b6f78..5deaddbd7927 100644
--- a/include/linux/anon_inodes.h
+++ b/include/linux/anon_inodes.h
@@ -15,6 +15,10 @@ struct inode;
struct file *anon_inode_getfile(const char *name,
const struct file_operations *fops,
void *priv, int flags);
+struct file *anon_inode_getfile_secure(const char *name,
+ const struct file_operations *fops,
+ void *priv, int flags,
+ const struct inode *context_inode);
int anon_inode_getfd(const char *name, const struct file_operations *fops,
void *priv, int flags);
int anon_inode_getfd_secure(const char *name,