From:   Casey Schaufler <casey@schaufler-ca.com>
To:     casey@schaufler-ca.com, paul@paul-moore.com,
        linux-security-module@vger.kernel.org
Cc:     jmorris@namei.org, keescook@chromium.org,
        john.johansen@canonical.com, penguin-kernel@i-love.sakura.ne.jp,
        stephen.smalley.work@gmail.com, linux-kernel@vger.kernel.org,
        linux-api@vger.kernel.org, mic@digikod.net
Subject: [PATCH v7 08/11] Smack: implement setselfattr and getselfattr hooks
Date:   Wed, 15 Mar 2023 15:47:01 -0700
Message-Id: <20230315224704.2672-9-casey@schaufler-ca.com>
In-Reply-To: <20230315224704.2672-1-casey@schaufler-ca.com>
References: <20230315224704.2672-1-casey@schaufler-ca.com>
MIME-Version: 1.0
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Implement Smack support for security_[gs]etselfattr.
Refactor the setprocattr hook to avoid code duplication.

Signed-off-by: Casey Schaufler <casey@schaufler-ca.com>
---
 security/smack/smack_lsm.c | 105 +++++++++++++++++++++++++++++++++++--
 1 file changed, 100 insertions(+), 5 deletions(-)

diff --git a/security/smack/smack_lsm.c b/security/smack/smack_lsm.c
index 3cf862fcbe08..b3e72b82ced9 100644
--- a/security/smack/smack_lsm.c
+++ b/security/smack/smack_lsm.c
@@ -3552,6 +3552,41 @@ static void smack_d_instantiate(struct dentry *opt_dentry, struct inode *inode)
 	return;
 }
 
+/**
+ * smack_getselfattr - Smack current process attribute
+ * @attr: which attribute to fetch
+ * @ctx: buffer to receive the result
+ * @size: available size in, actual size out
+ * @flags: unused
+ *
+ * Fill the passed user space @ctx with the details of the requested
+ * attribute.
+ *
+ * Returns 0 on success, an error code otherwise.
+ */
+static int smack_getselfattr(unsigned int __user attr,
+			     struct lsm_ctx __user *ctx, size_t *size,
+			     u32 __user flags)
+{
+	struct smack_known *skp = smk_of_current();
+	int total;
+	int slen;
+	int rc = 0;
+
+	if (attr != LSM_ATTR_CURRENT)
+		return -EOPNOTSUPP;
+
+	slen = strlen(skp->smk_known) + 1;
+	total = slen + sizeof(*ctx);
+	if (total > *size)
+		rc = -E2BIG;
+	else
+		lsm_fill_user_ctx(ctx, skp->smk_known, slen, LSM_ID_SMACK, 0);
+
+	*size = total;
+	return rc;
+}
+
 /**
  * smack_getprocattr - Smack process attribute access
  * @p: the object task
@@ -3581,8 +3616,8 @@ static int smack_getprocattr(struct task_struct *p, const char *name, char **val
 }
 
 /**
- * smack_setprocattr - Smack process attribute setting
- * @name: the name of the attribute in /proc/.../attr
+ * do_setattr - Smack process attribute setting
+ * @attr: the ID of the attribute
  * @value: the value to set
  * @size: the size of the value
  *
@@ -3591,7 +3626,7 @@ static int smack_getprocattr(struct task_struct *p, const char *name, char **val
  *
  * Returns the length of the smack label or an error code
  */
-static int smack_setprocattr(const char *name, void *value, size_t size)
+static int do_setattr(u64 attr, void *value, size_t size)
 {
 	struct task_smack *tsp = smack_cred(current_cred());
 	struct cred *new;
@@ -3605,8 +3640,8 @@ static int smack_setprocattr(const char *name, void *value, size_t size)
 	if (value == NULL || size == 0 || size >= SMK_LONGLABEL)
 		return -EINVAL;
 
-	if (strcmp(name, "current") != 0)
-		return -EINVAL;
+	if (attr != LSM_ATTR_CURRENT)
+		return -EOPNOTSUPP;
 
 	skp = smk_import_entry(value, size);
 	if (IS_ERR(skp))
@@ -3645,6 +3680,64 @@ static int smack_setprocattr(const char *name, void *value, size_t size)
 	return size;
 }
 
+/**
+ * smack_setselfattr - Set a Smack process attribute
+ * @attr: which attribute to set
+ * @ctx: buffer containing the data
+ * @size: size of @ctx
+ * @flags: unused
+ *
+ * Fill the passed user space @ctx with the details of the requested
+ * attribute.
+ *
+ * Returns 0 on success, an error code otherwise.
+ */
+static int smack_setselfattr(unsigned int __user attr,
+			     struct lsm_ctx __user *ctx, size_t __user size,
+			     u32 __user flags)
+{
+	struct lsm_ctx *lctx;
+	void *context;
+	int rc;
+
+	context = kmalloc(size, GFP_KERNEL);
+	if (context == NULL)
+		return -ENOMEM;
+
+	lctx = (struct lsm_ctx *)context;
+	if (copy_from_user(context, ctx, size))
+		rc = -EFAULT;
+	else if (lctx->ctx_len > size)
+		rc = -EINVAL;
+	else
+		rc = do_setattr(attr, lctx + 1, lctx->ctx_len);
+
+	kfree(context);
+	if (rc > 0)
+		return 0;
+	return rc;
+}
+
+/**
+ * smack_setprocattr - Smack process attribute setting
+ * @name: the name of the attribute in /proc/.../attr
+ * @value: the value to set
+ * @size: the size of the value
+ *
+ * Sets the Smack value of the task. Only setting self
+ * is permitted and only with privilege
+ *
+ * Returns the length of the smack label or an error code
+ */
+static int smack_setprocattr(const char *name, void *value, size_t size)
+{
+	int attr = lsm_name_to_attr(name);
+
+	if (attr)
+		return do_setattr(attr, value, size);
+	return -EINVAL;
+}
+
 /**
  * smack_unix_stream_connect - Smack access on UDS
  * @sock: one sock
@@ -4955,6 +5048,8 @@ static struct security_hook_list smack_hooks[] __lsm_ro_after_init = {
 
 	LSM_HOOK_INIT(d_instantiate, smack_d_instantiate),
 
+	LSM_HOOK_INIT(getselfattr, smack_getselfattr),
+	LSM_HOOK_INIT(setselfattr, smack_setselfattr),
 	LSM_HOOK_INIT(getprocattr, smack_getprocattr),
 	LSM_HOOK_INIT(setprocattr, smack_setprocattr),
 
-- 
2.39.2