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Date: Wed, 6 Jan 2021 21:09:49 -0500
From: Paul Moore <paul@...l-moore.com>
To: Lokesh Gidra <lokeshgidra@...gle.com>
Cc: Andrea Arcangeli <aarcange@...hat.com>,
Alexander Viro <viro@...iv.linux.org.uk>,
James Morris <jmorris@...ei.org>,
Stephen Smalley <stephen.smalley.work@...il.com>,
Casey Schaufler <casey@...aufler-ca.com>,
Eric Biggers <ebiggers@...nel.org>,
"Serge E. Hallyn" <serge@...lyn.com>,
Eric Paris <eparis@...isplace.org>,
Daniel Colascione <dancol@...col.org>,
Kees Cook <keescook@...omium.org>,
"Eric W. Biederman" <ebiederm@...ssion.com>,
KP Singh <kpsingh@...gle.com>,
David Howells <dhowells@...hat.com>,
Anders Roxell <anders.roxell@...aro.org>,
Sami Tolvanen <samitolvanen@...gle.com>,
Matthew Garrett <matthewgarrett@...gle.com>,
Aaron Goidel <acgoide@...ho.nsa.gov>,
Randy Dunlap <rdunlap@...radead.org>,
"Joel Fernandes (Google)" <joel@...lfernandes.org>,
YueHaibing <yuehaibing@...wei.com>,
Christian Brauner <christian.brauner@...ntu.com>,
Alexei Starovoitov <ast@...nel.org>,
Alexey Budankov <alexey.budankov@...ux.intel.com>,
Adrian Reber <areber@...hat.com>,
Aleksa Sarai <cyphar@...har.com>,
linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
linux-security-module@...r.kernel.org, selinux@...r.kernel.org,
kaleshsingh@...gle.com, calin@...gle.com, surenb@...gle.com,
jeffv@...gle.com, kernel-team@...roid.com, linux-mm@...ck.org,
Andrew Morton <akpm@...ux-foundation.org>, hch@...radead.org,
Daniel Colascione <dancol@...gle.com>,
Eric Biggers <ebiggers@...gle.com>
Subject: Re: [PATCH v13 2/4] fs: add LSM-supporting anon-inode interface
On Wed, Nov 11, 2020 at 8:54 PM Lokesh Gidra <lokeshgidra@...gle.com> wrote:
> From: Daniel Colascione <dancol@...gle.com>
>
> This change adds a new function, anon_inode_getfd_secure, that creates
> anonymous-node file with individual non-S_PRIVATE inode 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 function accepts an optional context_inode parameter that callers
> can use to provide additional contextual information to security modules.
> For example, in case of userfaultfd, the created inode is a 'logical child'
> of the context_inode (userfaultfd inode of the parent process) in the sense
> that it provides the security context required during creation of the child
> process' userfaultfd inode.
>
> Signed-off-by: Daniel Colascione <dancol@...gle.com>
>
> [Delete obsolete comments to alloc_anon_inode()]
> [Add context_inode description in comments to anon_inode_getfd_secure()]
> [Remove definition of anon_inode_getfile_secure() as there are no callers]
> [Make __anon_inode_getfile() static]
> [Use correct error cast in __anon_inode_getfile()]
> [Fix error handling in __anon_inode_getfile()]
Lokesh, I'm assuming you made the changes in the brackets above? If
so they should include your initials or some other means of
attributing them to you, e.g. "[LG: Fix error ...]".
> Signed-off-by: Lokesh Gidra <lokeshgidra@...gle.com>
> Reviewed-by: Eric Biggers <ebiggers@...gle.com>
> ---
> fs/anon_inodes.c | 150 ++++++++++++++++++++++++++----------
> fs/libfs.c | 5 --
> include/linux/anon_inodes.h | 5 ++
> 3 files changed, 115 insertions(+), 45 deletions(-)
>
> diff --git a/fs/anon_inodes.c b/fs/anon_inodes.c
> index 89714308c25b..023337d65a03 100644
> --- a/fs/anon_inodes.c
> +++ b/fs/anon_inodes.c
> @@ -55,61 +55,79 @@ 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)
> {
> - struct file *file;
> + 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 inode;
> + inode->i_flags &= ~S_PRIVATE;
> + error = security_inode_init_security_anon(inode, &qname, context_inode);
> + if (error) {
> + iput(inode);
> + return ERR_PTR(error);
> + }
> + return inode;
> +}
>
> - if (IS_ERR(anon_inode_inode))
> - return ERR_PTR(-ENODEV);
> +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)
Is it necessary to pass both the context_inode pointer and the secure
boolean? It seems like if context_inode is non-NULL then one could
assume that a secure anonymous inode was requested; is there ever
going to be a case where this is not true?
> +{
> + 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 (secure) {
> + inode = anon_inode_make_secure_inode(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;
> }
> -EXPORT_SYMBOL_GPL(anon_inode_getfile);
--
paul moore
www.paul-moore.com
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