1 files changed, 256 insertions, 57 deletions

diff --git a/fs/anon_inodes.c b/fs/anon_inodes.c
index 91262c34b797..b8381c7fb636 100644
--- a/fs/anon_inodes.c
+++ b/fs/anon_inodes.c
@@ -1,3 +1,4 @@
+// SPDX-License-Identifier: GPL-2.0-only
 /*
  *  fs/anon_inodes.c
  *
@@ -19,18 +20,60 @@
 #include <linux/kernel.h>
 #include <linux/magic.h>
 #include <linux/anon_inodes.h>
+#include <linux/pseudo_fs.h>
 
 #include <linux/uaccess.h>
 
-static struct vfsmount *anon_inode_mnt __read_mostly;
-static struct inode *anon_inode_inode;
+#include "internal.h"
+
+static struct vfsmount *anon_inode_mnt __ro_after_init;
+static struct inode *anon_inode_inode __ro_after_init;
+
+/*
+ * User space expects anonymous inodes to have no file type in st_mode.
+ *
+ * In particular, 'lsof' has this legacy logic:
+ *
+ *	type = s->st_mode & S_IFMT;
+ *	switch (type) {
+ *	  ...
+ *	case 0:
+ *		if (!strcmp(p, "anon_inode"))
+ *			Lf->ntype = Ntype = N_ANON_INODE;
+ *
+ * to detect our old anon_inode logic.
+ *
+ * Rather than mess with our internal sane inode data, just fix it
+ * up here in getattr() by masking off the format bits.
+ */
+int anon_inode_getattr(struct mnt_idmap *idmap, const struct path *path,
+		       struct kstat *stat, u32 request_mask,
+		       unsigned int query_flags)
+{
+	struct inode *inode = d_inode(path->dentry);
+
+	generic_fillattr(&nop_mnt_idmap, request_mask, inode, stat);
+	stat->mode &= ~S_IFMT;
+	return 0;
+}
+
+int anon_inode_setattr(struct mnt_idmap *idmap, struct dentry *dentry,
+		       struct iattr *attr)
+{
+	return -EOPNOTSUPP;
+}
+
+static const struct inode_operations anon_inode_operations = {
+	.getattr = anon_inode_getattr,
+	.setattr = anon_inode_setattr,
+};
 
 /*
  * anon_inodefs_dname() is called from d_path().
  */
 static char *anon_inodefs_dname(struct dentry *dentry, char *buffer, int buflen)
 {
-	return dynamic_dname(dentry, buffer, buflen, "anon_inode:%s",
+	return dynamic_dname(buffer, buflen, "anon_inode:%s",
 				dentry->d_name.name);
 }
 
@@ -38,112 +81,267 @@ static const struct dentry_operations anon_inodefs_dentry_operations = {
 	.d_dname	= anon_inodefs_dname,
 };
 
-static struct dentry *anon_inodefs_mount(struct file_system_type *fs_type,
-				int flags, const char *dev_name, void *data)
+static int anon_inodefs_init_fs_context(struct fs_context *fc)
 {
-	return mount_pseudo(fs_type, "anon_inode:", NULL,
-			&anon_inodefs_dentry_operations, ANON_INODE_FS_MAGIC);
+	struct pseudo_fs_context *ctx = init_pseudo(fc, ANON_INODE_FS_MAGIC);
+	if (!ctx)
+		return -ENOMEM;
+	fc->s_iflags |= SB_I_NOEXEC;
+	fc->s_iflags |= SB_I_NODEV;
+	ctx->dops = &anon_inodefs_dentry_operations;
+	return 0;
 }
 
 static struct file_system_type anon_inode_fs_type = {
 	.name		= "anon_inodefs",
-	.mount		= anon_inodefs_mount,
+	.init_fs_context = anon_inodefs_init_fs_context,
 	.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
+ * anon_inode_make_secure_inode - allocate an anonymous inode with security context
+ * @sb:		[in]	Superblock to allocate from
+ * @name:	[in]	Name of the class of the newfile (e.g., "secretmem")
+ * @context_inode:
+ *		[in]	Optional parent inode for security inheritance
  *
- * @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
+ * The function ensures proper security initialization through the LSM hook
+ * security_inode_init_security_anon().
  *
- * 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.
+ * Return:	Pointer to new inode on success, ERR_PTR on failure.
  */
-struct file *anon_inode_getfile(const char *name,
-				const struct file_operations *fops,
-				void *priv, int flags)
+struct inode *anon_inode_make_secure_inode(struct super_block *sb, const char *name,
+					   const struct inode *context_inode)
 {
-	struct file *file;
+	struct inode *inode;
+	int error;
 
-	if (IS_ERR(anon_inode_inode))
-		return ERR_PTR(-ENODEV);
+	inode = alloc_anon_inode(sb);
+	if (IS_ERR(inode))
+		return inode;
+	inode->i_flags &= ~S_PRIVATE;
+	inode->i_op = &anon_inode_operations;
+	error =	security_inode_init_security_anon(inode, &QSTR(name),
+						  context_inode);
+	if (error) {
+		iput(inode);
+		return ERR_PTR(error);
+	}
+	return inode;
+}
+EXPORT_SYMBOL_FOR_MODULES(anon_inode_make_secure_inode, "kvm");
+
+static struct file *__anon_inode_getfile(const char *name,
+					 const struct file_operations *fops,
+					 void *priv, int flags,
+					 const struct inode *context_inode,
+					 bool make_inode)
+{
+	struct inode *inode;
+	struct file *file;
 
 	if (fops->owner && !try_module_get(fops->owner))
 		return ERR_PTR(-ENOENT);
 
-	/*
-	 * We know the anon_inode inode count is always greater than zero,
-	 * so ihold() is safe.
-	 */
-	ihold(anon_inode_inode);
-	file = alloc_file_pseudo(anon_inode_inode, anon_inode_mnt, name,
+	if (make_inode) {
+		inode =	anon_inode_make_secure_inode(anon_inode_mnt->mnt_sb,
+						     name, context_inode);
+		if (IS_ERR(inode)) {
+			file = ERR_CAST(inode);
+			goto err;
+		}
+	} else {
+		inode =	anon_inode_inode;
+		if (IS_ERR(inode)) {
+			file = ERR_PTR(-ENODEV);
+			goto err;
+		}
+		/*
+		 * We know the anon_inode inode count is always
+		 * greater than zero, so ihold() is safe.
+		 */
+		ihold(inode);
+	}
+
+	file = alloc_file_pseudo(inode, anon_inode_mnt, name,
 				 flags & (O_ACCMODE | O_NONBLOCK), fops);
 	if (IS_ERR(file))
-		goto err;
+		goto err_iput;
 
-	file->f_mapping = anon_inode_inode->i_mapping;
+	file->f_mapping = inode->i_mapping;
 
 	file->private_data = priv;
 
 	return file;
 
+err_iput:
+	iput(inode);
 err:
-	iput(anon_inode_inode);
 	module_put(fops->owner);
 	return file;
 }
+
+/**
+ * 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)
+{
+	return __anon_inode_getfile(name, fops, priv, flags, NULL, false);
+}
 EXPORT_SYMBOL_GPL(anon_inode_getfile);
 
 /**
- * anon_inode_getfd - creates a new file instance by hooking it up to an
- *                    anonymous inode, and a dentry that describe the "class"
- *                    of the file
+ * anon_inode_getfile_fmode - 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
+ * @f_mode:  [in]    fmode
  *
  * 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_getfd() will share a single inode,
+ * 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 new descriptor or an error code.
+ * setup. Allows setting the fmode. Returns the newly created file* or an error
+ * pointer.
  */
-int anon_inode_getfd(const char *name, const struct file_operations *fops,
-		     void *priv, int flags)
+struct file *anon_inode_getfile_fmode(const char *name,
+				const struct file_operations *fops,
+				void *priv, int flags, fmode_t f_mode)
 {
-	int error, fd;
 	struct file *file;
 
-	error = get_unused_fd_flags(flags);
-	if (error < 0)
-		return error;
-	fd = error;
+	file = __anon_inode_getfile(name, fops, priv, flags, NULL, false);
+	if (!IS_ERR(file))
+		file->f_mode |= f_mode;
 
-	file = anon_inode_getfile(name, fops, priv, flags);
-	if (IS_ERR(file)) {
-		error = PTR_ERR(file);
-		goto err_put_unused_fd;
-	}
-	fd_install(fd, file);
+	return file;
+}
+EXPORT_SYMBOL_GPL(anon_inode_getfile_fmode);
+
+/**
+ * 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.
+ *
+ * @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)
+ *
+ * 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.
+ */
+struct file *anon_inode_create_getfile(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);
+}
+EXPORT_SYMBOL_GPL(anon_inode_create_getfile);
 
-	return fd;
+static int __anon_inode_getfd(const char *name,
+			      const struct file_operations *fops,
+			      void *priv, int flags,
+			      const struct inode *context_inode,
+			      bool make_inode)
+{
+	return FD_ADD(flags, __anon_inode_getfile(name, fops, priv, flags,
+						  context_inode, make_inode));
+}
 
-err_put_unused_fd:
-	put_unused_fd(fd);
-	return error;
+/**
+ * anon_inode_getfd - 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_getfd() will use the same singleton inode, reducing
+ * memory use and avoiding code duplication for the file/inode/dentry
+ * setup.  Returns a newly created file descriptor or an error code.
+ */
+int anon_inode_getfd(const char *name, const struct file_operations *fops,
+		     void *priv, int flags)
+{
+	return __anon_inode_getfd(name, fops, priv, flags, NULL, false);
 }
 EXPORT_SYMBOL_GPL(anon_inode_getfd);
 
+/**
+ * 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.
+ *
+ * @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)
+ *
+ * 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_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);
+}
+
+
 static int __init anon_inode_init(void)
 {
 	anon_inode_mnt = kern_mount(&anon_inode_fs_type);
@@ -153,6 +351,7 @@ static int __init anon_inode_init(void)
 	anon_inode_inode = alloc_anon_inode(anon_inode_mnt->mnt_sb);
 	if (IS_ERR(anon_inode_inode))
 		panic("anon_inode_init() inode allocation failed (%ld)\n", PTR_ERR(anon_inode_inode));
+	anon_inode_inode->i_op = &anon_inode_operations;
 
 	return 0;
 }