[PATCH v9 08/11] Smack: implement setselfattr and getselfattr hooks

Casey Schaufler
2023-04-21T17:47:00Z

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..902b39c187bf 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 1, the number of attributes, 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 = 1;
+
+ if (attr != LSM_ATTR_CURRENT)
+ return -EOPNOTSUPP;
+
+ slen = strlen(skp->smk_known) + 1;
+ total = ALIGN(slen + sizeof(*ctx), 8);
+ 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