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Date: Sat, 11 Dec 2021 12:00:38 +0100
From: Christian Brauner <christian.brauner@...ntu.com>
To: Stefan Berger <stefanb@...ux.ibm.com>
Cc: linux-integrity@...r.kernel.org, zohar@...ux.ibm.com,
serge@...lyn.com, containers@...ts.linux.dev,
dmitry.kasatkin@...il.com, ebiederm@...ssion.com,
krzysztof.struczynski@...wei.com, roberto.sassu@...wei.com,
mpeters@...hat.com, lhinds@...hat.com, lsturman@...hat.com,
puiterwi@...hat.com, jejb@...ux.ibm.com, jamjoom@...ibm.com,
linux-kernel@...r.kernel.org, paul@...l-moore.com, rgb@...hat.com,
linux-security-module@...r.kernel.org, jmorris@...ei.org
Subject: Re: [PATCH v6 14/17] ima: Tie opened SecurityFS files to the IMA
namespace it belongs to
On Fri, Dec 10, 2021 at 02:47:33PM -0500, Stefan Berger wrote:
> Tie IMA's files in SecurityFS to the IMA namespace they belong to so that
> also file descriptor that were passed or inherited to other user/IMA
> namespaces will always access the data of the IMA namespace they originally
> belonged to.
>
> Signed-off-by: Stefan Berger <stefanb@...ux.ibm.com>
> ---
> security/integrity/ima/ima_fs.c | 74 ++++++++++++++++++++++++-----
> security/integrity/ima/ima_policy.c | 4 +-
> 2 files changed, 63 insertions(+), 15 deletions(-)
>
> diff --git a/security/integrity/ima/ima_fs.c b/security/integrity/ima/ima_fs.c
> index 0e582ceecc7f..a136d14f29ec 100644
> --- a/security/integrity/ima/ima_fs.c
> +++ b/security/integrity/ima/ima_fs.c
> @@ -35,6 +35,20 @@ static int __init default_canonical_fmt_setup(char *str)
> }
> __setup("ima_canonical_fmt", default_canonical_fmt_setup);
>
> +static inline struct user_namespace *ima_user_ns_from_file(struct file *filp)
> +{
> + return filp->f_path.mnt->mnt_sb->s_user_ns;
> +}
I'd probably rewrite this as:
static inline struct user_namespace *ima_user_ns_from_file(const struct file *filp)
{
return file_inode(filp)->i_sb->s_user_ns;
}
as it spares you some pointer chasing and also looks cleaner.
> +
> +static int ima_open(struct inode *inode, struct file *file)
> +{
> + struct user_namespace *user_ns = ima_user_ns_from_file(file);
> + struct ima_namespace *ns = user_ns->ima_ns;
> +
> + file->private_data = ns;
> + return 0;
> +}
> +
> static ssize_t ima_show_htable_value(char __user *buf, size_t count,
> loff_t *ppos, atomic_long_t *val)
> {
> @@ -49,12 +63,13 @@ static ssize_t ima_show_htable_violations(struct file *filp,
> char __user *buf,
> size_t count, loff_t *ppos)
> {
> - struct ima_namespace *ns = get_current_ns();
> + struct ima_namespace *ns = filp->private_data;
>
> return ima_show_htable_value(buf, count, ppos, &ns->ima_htable.violations);
> }
>
> static const struct file_operations ima_htable_violations_ops = {
> + .open = ima_open,
> .read = ima_show_htable_violations,
> .llseek = generic_file_llseek,
> };
> @@ -63,12 +78,13 @@ static ssize_t ima_show_measurements_count(struct file *filp,
> char __user *buf,
> size_t count, loff_t *ppos)
> {
> - struct ima_namespace *ns = get_current_ns();
> + struct ima_namespace *ns = filp->private_data;
>
> return ima_show_htable_value(buf, count, ppos, &ns->ima_htable.len);
> }
>
> static const struct file_operations ima_measurements_count_ops = {
> + .open = ima_open,
> .read = ima_show_measurements_count,
> .llseek = generic_file_llseek,
> };
> @@ -76,7 +92,7 @@ static const struct file_operations ima_measurements_count_ops = {
> /* returns pointer to hlist_node */
> static void *ima_measurements_start(struct seq_file *m, loff_t *pos)
> {
> - struct ima_namespace *ns = get_current_ns();
> + struct ima_namespace *ns = m->private;
> loff_t l = *pos;
> struct ima_queue_entry *qe;
>
> @@ -94,7 +110,7 @@ static void *ima_measurements_start(struct seq_file *m, loff_t *pos)
>
> static void *ima_measurements_next(struct seq_file *m, void *v, loff_t *pos)
> {
> - struct ima_namespace *ns = get_current_ns();
> + struct ima_namespace *ns = m->private;
> struct ima_queue_entry *qe = v;
>
> /* lock protects when reading beyond last element
> @@ -195,9 +211,26 @@ static const struct seq_operations ima_measurments_seqops = {
> .show = ima_measurements_show
> };
>
> +static int ima_seq_open(struct file *file, const struct seq_operations *seq_ops)
> +{
> + struct user_namespace *user_ns = ima_user_ns_from_file(file);
> + struct ima_namespace *ns = user_ns->ima_ns;
> + struct seq_file *seq;
> + int err;
> +
> + err = seq_open(file, seq_ops);
> + if (err)
> + return err;
> +
> + seq = file->private_data;
> + seq->private = ns;
> +
> + return 0;
> +}
> +
> static int ima_measurements_open(struct inode *inode, struct file *file)
> {
> - return seq_open(file, &ima_measurments_seqops);
> + return ima_seq_open(file, &ima_measurments_seqops);
> }
>
> static const struct file_operations ima_measurements_ops = {
> @@ -263,7 +296,7 @@ static const struct seq_operations ima_ascii_measurements_seqops = {
>
> static int ima_ascii_measurements_open(struct inode *inode, struct file *file)
> {
> - return seq_open(file, &ima_ascii_measurements_seqops);
> + return ima_seq_open(file, &ima_ascii_measurements_seqops);
> }
>
> static const struct file_operations ima_ascii_measurements_ops = {
> @@ -273,9 +306,8 @@ static const struct file_operations ima_ascii_measurements_ops = {
> .release = seq_release,
> };
>
> -static ssize_t ima_read_policy(char *path)
> +static ssize_t ima_read_policy(struct ima_namespace *ns, char *path)
> {
> - struct ima_namespace *ns = get_current_ns();
> void *data = NULL;
> char *datap;
> size_t size;
> @@ -314,10 +346,23 @@ static ssize_t ima_read_policy(char *path)
> return pathlen;
> }
>
> +static struct ima_namespace *ima_filp_private(struct file *filp)
> +{
> + if (!(filp->f_flags & O_WRONLY)) {
> +#ifdef CONFIG_IMA_READ_POLICY
> + struct seq_file *seq;
> +
> + seq = filp->private_data;
> + return seq->private;
> +#endif
> + }
> + return filp->private_data;
> +}
All of that isn't needed with my last proposal. You don't need to stash
anything anywhere. I showed that in my previous patch suggestion. The
original filp is stashed in the seq_file's private member, i.e. taking
ima_measurements_start(struct seq_file *m, loff_t *pos)
you can get at:
const struct file *filp = m->file;
struct user_namespace *user_ns = file_inode(filp)->i_sb->s_user_ns;
struct ima_namespace *ns = user_ns->ima_ns;
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