Commit 4f0b9194 authored by Paolo Bonzini's avatar Paolo Bonzini
Browse files

fs: Rename anon_inode_getfile_secure() and anon_inode_getfd_secure() 



The call to the inode_init_security_anon() LSM hook is not the sole
reason to use anon_inode_getfile_secure() or anon_inode_getfd_secure().
For example, the functions also allow one to create a file with non-zero
size, without needing a full-blown filesystem.  In this case, you don't
need a "secure" version, just unique inodes; the current name of the
functions is confusing and does not explain well the difference with
the more "standard" anon_inode_getfile() and anon_inode_getfd().

Of course, there is another side of the coin; neither io_uring nor
userfaultfd strictly speaking need distinct inodes, and it is not
that clear anymore that anon_inode_create_get{file,fd}() allow the LSM
to intercept and block the inode's creation.  If one was so inclined,
anon_inode_getfile_secure() and anon_inode_getfd_secure() could be kept,
using the shared inode or a new one depending on CONFIG_SECURITY.
However, this is probably overkill, and potentially a cause of bugs in
different configurations.  Therefore, just add a comment to io_uring
and userfaultfd explaining the choice of the function.

While at it, remove the export for what is now anon_inode_create_getfd().
There is no in-tree module that uses it, and the old name is gone anyway.
If anybody actually needs the symbol, they can ask or they can just use
anon_inode_create_getfile(), which will be exported very soon for use
in KVM.

Suggested-by: default avatarChristian Brauner <brauner@kernel.org>
Reviewed-by: default avatarChristian Brauner <brauner@kernel.org>
Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
parent 0003e2a4

fs/anon_inodes.c

+33 −17
Original line number Diff line number Diff line
@@ -79,7 +79,7 @@ static struct file *__anon_inode_getfile(const char *name, 
					 const struct file_operations *fops,

					 void *priv, int flags,

					 const struct inode *context_inode,

					 bool secure)

					 bool make_inode)

{

	struct inode *inode;

	struct file *file;
@@ -87,7 +87,7 @@ static struct file *__anon_inode_getfile(const char *name, 
	if (fops->owner && !try_module_get(fops->owner))

		return ERR_PTR(-ENOENT);



	if (secure) {

	if (make_inode) {

		inode =	anon_inode_make_secure_inode(name, context_inode);

		if (IS_ERR(inode)) {

			file = ERR_CAST(inode);
@@ -149,13 +149,10 @@ 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

 * anon_inode_create_getfile - 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.

 *                             inode_init_security_anon() LSM hook.

 *

 * @name:    [in]    name of the "class" of the new file

 * @fops:    [in]    file operations for the new file
@@ -164,11 +161,21 @@ EXPORT_SYMBOL_GPL(anon_inode_getfile); 
 * @context_inode:

 *           [in]    the logical relationship with the new inode (optional)

 *

 * Create a new anonymous inode and file pair.  This can be done for two

 * reasons:

 *

 * - for the inode to have its own security context, so that LSMs can enforce

 *   policy on the inode's creation;

 *

 * - if the caller needs a unique inode, for example in order to customize

 *   the size returned by fstat()

 *

 * 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.

 * reference to it is not held.

 *

 * Returns the newly created file* or an error pointer.

 */

struct file *anon_inode_getfile_secure(const char *name,

struct file *anon_inode_create_getfile(const char *name,

				       const struct file_operations *fops,

				       void *priv, int flags,

				       const struct inode *context_inode)
@@ -181,7 +188,7 @@ static int __anon_inode_getfd(const char *name, 
			      const struct file_operations *fops,

			      void *priv, int flags,

			      const struct inode *context_inode,

			      bool secure)

			      bool make_inode)

{

	int error, fd;

	struct file *file;
@@ -192,7 +199,7 @@ static int __anon_inode_getfd(const char *name, 
	fd = error;



	file = __anon_inode_getfile(name, fops, priv, flags, context_inode,

				    secure);

				    make_inode);

	if (IS_ERR(file)) {

		error = PTR_ERR(file);

		goto err_put_unused_fd;
@@ -231,10 +238,9 @@ int anon_inode_getfd(const char *name, const struct file_operations *fops, 
EXPORT_SYMBOL_GPL(anon_inode_getfd);



/**

 * anon_inode_getfd_secure - Like anon_inode_getfd(), but creates a new

 * anon_inode_create_getfd - Like anon_inode_getfd(), 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 the inode to have its

 * own security context and for a LSM to reject creation of the inode.

 * the inode_init_security_anon() LSM hook.

 *

 * @name:    [in]    name of the "class" of the new file

 * @fops:    [in]    file operations for the new file
@@ -243,16 +249,26 @@ EXPORT_SYMBOL_GPL(anon_inode_getfd); 
 * @context_inode:

 *           [in]    the logical relationship with the new inode (optional)

 *

 * Create a new anonymous inode and file pair.  This can be done for two

 * reasons:

 *

 * - for the inode to have its own security context, so that LSMs can enforce

 *   policy on the inode's creation;

 *

 * - if the caller needs a unique inode, for example in order to customize

 *   the size returned by fstat()

 *

 * The LSM may use @context_inode in inode_init_security_anon(), but a

 * reference to it is not held.

 *

 * Returns a newly created file descriptor or an error code.

 */

int anon_inode_getfd_secure(const char *name, const struct file_operations *fops,

int anon_inode_create_getfd(const char *name, const struct file_operations *fops,

			    void *priv, int flags,

			    const struct inode *context_inode)

{

	return __anon_inode_getfd(name, fops, priv, flags, context_inode, true);

}

EXPORT_SYMBOL_GPL(anon_inode_getfd_secure);



static int __init anon_inode_init(void)

{

fs/userfaultfd.c

+3 −2
Original line number Diff line number Diff line
@@ -1033,7 +1033,7 @@ static int resolve_userfault_fork(struct userfaultfd_ctx *new, 
{

	int fd;



	fd = anon_inode_getfd_secure("[userfaultfd]", &userfaultfd_fops, new,

	fd = anon_inode_create_getfd("[userfaultfd]", &userfaultfd_fops, new,

			O_RDONLY | (new->flags & UFFD_SHARED_FCNTL_FLAGS), inode);

	if (fd < 0)

		return fd;
@@ -2205,7 +2205,8 @@ static int new_userfaultfd(int flags) 
	/* prevent the mm struct to be freed */

	mmgrab(ctx->mm);



	fd = anon_inode_getfd_secure("[userfaultfd]", &userfaultfd_fops, ctx,

	/* Create a new inode so that the LSM can block the creation.  */

	fd = anon_inode_create_getfd("[userfaultfd]", &userfaultfd_fops, ctx,

			O_RDONLY | (flags & UFFD_SHARED_FCNTL_FLAGS), NULL);

	if (fd < 0) {

		mmdrop(ctx->mm);

include/linux/anon_inodes.h

+2 −2
Original line number Diff line number Diff line
@@ -15,13 +15,13 @@ 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,

struct file *anon_inode_create_getfile(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,

int anon_inode_create_getfd(const char *name,

			    const struct file_operations *fops,

			    void *priv, int flags,

			    const struct inode *context_inode);

io_uring/io_uring.c

+2 −1
Original line number Diff line number Diff line
@@ -3835,7 +3835,8 @@ static struct file *io_uring_get_file(struct io_ring_ctx *ctx) 
		return ERR_PTR(ret);

#endif



	file = anon_inode_getfile_secure("[io_uring]", &io_uring_fops, ctx,

	/* Create a new inode so that the LSM can block the creation.  */

	file = anon_inode_create_getfile("[io_uring]", &io_uring_fops, ctx,

					 O_RDWR | O_CLOEXEC, NULL);

#if defined(CONFIG_UNIX)

	if (IS_ERR(file)) {