[PATCH bpf-next v4 08/20] lsm: Refactor return value of LSM hook getprocattr

Xu Kuohai
2024-07-11T11:14:00Z

From: Xu Kuohai <xukuohai@huawei.com>

To be consistent with most LSM hooks, convert the return value of
hook getprocattr to 0 or a negative error code.

Before:
- Hook getprocattr returns length of value on success or a negative
error code on failure.

After:
- Hook getprocattr returns 0 on success or a negative error code on
failure. An output parameter @len is introduced to hold the
length of value on success.

Signed-off-by: Xu Kuohai <xukuohai@huawei.com>
---
fs/proc/base.c | 5 ++++-
include/linux/lsm_hook_defs.h | 2 +-
include/linux/security.h | 5 +++--
security/apparmor/lsm.c | 7 +++++--
security/security.c | 8 +++++---
security/selinux/hooks.c | 16 +++++++++-------
security/smack/smack_lsm.c | 11 ++++++-----
7 files changed, 33 insertions(+), 21 deletions(-)

diff --git a/fs/proc/base.c b/fs/proc/base.c
index 9e1cf6cc674d..516a00f6ce36 100644
--- a/fs/proc/base.c
+++ b/fs/proc/base.c
@@ -2721,13 +2721,16 @@ static ssize_t proc_pid_attr_read(struct file * file, char __user * buf,
char *p = NULL;
ssize_t length;
struct task_struct *task = get_proc_task(inode);
+ u32 n;

if (!task)
return -ESRCH;

length = security_getprocattr(task, PROC_I(inode)->op.lsmid,
file->f_path.dentry->d_name.name,
- &p);
+ &p, &n);
+ if (!length)
+ length = n;
put_task_struct(task);
if (length > 0)
length = simple_read_from_buffer(buf, count, ppos, p, length);
diff --git a/include/linux/lsm_hook_defs.h b/include/linux/lsm_hook_defs.h
index 2628514bb19c..b0e3cf3fc33f 100644
--- a/include/linux/lsm_hook_defs.h
+++ b/include/linux/lsm_hook_defs.h
@@ -286,7 +286,7 @@ LSM_HOOK(int, -EOPNOTSUPP, getselfattr, unsigned int attr,
LSM_HOOK(int, -EOPNOTSUPP, setselfattr, unsigned int attr,
struct lsm_ctx *ctx, u32 size, u32 flags)
LSM_HOOK(int, -EINVAL, getprocattr, struct task_struct *p, const char *name,
- char **value)
+ char **value, u32 *len)
LSM_HOOK(int, -EINVAL, setprocattr, const char *name, void *value, size_t size,
size_t *wbytes)
LSM_HOOK(int, 0, ismaclabel, const char *name)
diff --git a/include/linux/security.h b/include/linux/security.h
index 1f1a9696e65d..616047030a89 100644
--- a/include/linux/security.h
+++ b/include/linux/security.h
@@ -495,7 +495,7 @@ int security_getselfattr(unsigned int attr, struct lsm_ctx __user *ctx,
int security_setselfattr(unsigned int attr, struct lsm_ctx __user *ctx,
u32 size, u32 flags);
int security_getprocattr(struct task_struct *p, int lsmid, const char *name,
- char **value);
+ char **value, u32 *len);
int security_setprocattr(int lsmid, const char *name, void *value, size_t size,
size_t *wbytes);
int security_netlink_send(struct sock *sk, struct sk_buff *skb);
@@ -1435,7 +1435,8 @@ static inline int security_setselfattr(unsigned int attr,
}

static inline int security_getprocattr(struct task_struct *p, int lsmid,
- const char *name, char **value)
+ const char *name, char **value,
+ u32 *len)
{
return -EINVAL;
}
diff --git a/security/apparmor/lsm.c b/security/apparmor/lsm.c
index 6c8b1f8c5781..0454f3f1af06 100644
--- a/security/apparmor/lsm.c
+++ b/security/apparmor/lsm.c
@@ -820,7 +820,7 @@ static int apparmor_getselfattr(unsigned int attr, struct lsm_ctx __user *lx,
}

static int apparmor_getprocattr(struct task_struct *task, const char *name,
- char **value)
+ char **value, u32 *len)
{
int error = -ENOENT;
/* released below */
@@ -843,7 +843,10 @@ static int apparmor_getprocattr(struct task_struct *task, const char *name,
aa_put_label(label);
put_cred(cred);

- return error;
+ if (error < 0)
+ return error;
+ *len = error;
+ return 0;
}

static int do_setattr(u64 attr, void *value, size_t size)
diff --git a/security/security.c b/security/security.c
index 9685096dbf16..9dd2ae6cf763 100644
--- a/security/security.c
+++ b/security/security.c
@@ -4117,20 +4117,22 @@ int security_setselfattr(unsigned int attr, struct lsm_ctx __user *uctx,
* @lsmid: LSM identification
* @name: attribute name
* @value: attribute value
+ * @len: length of @value
*
* Read attribute @name for task @p and store it into @value if allowed.
*
- * Return: Returns the length of @value on success, a negative value otherwise.
+ * Return: Returns 0 on success or a negative error code on failure.
+ * @len is set to the length of @value on success.
*/
int security_getprocattr(struct task_struct *p, int lsmid, const char *name,
- char **value)
+ char **value, u32 *len)
{
struct security_hook_list *hp;

hlist_for_each_entry(hp, &security_hook_heads.getprocattr, list) {
if (lsmid != 0 && lsmid != hp->lsmid->id)
continue;
- return hp->hook.getprocattr(p, name, value);
+ return hp->hook.getprocattr(p, name, value, len);
}
return LSM_RET_DEFAULT(getprocattr);
}
diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c
index 7a73f3710025..16cd336aab3d 100644
--- a/security/selinux/hooks.c
+++ b/security/selinux/hooks.c
@@ -6574,19 +6574,21 @@ static int selinux_setselfattr(unsigned int attr, struct lsm_ctx *ctx,
return rc;
}

-static int selinux_getprocattr(struct task_struct *p,
- const char *name, char **value)
+static int selinux_getprocattr(struct task_struct *p, const char *name,
+ char **value, u32 *len)
{
unsigned int attr = lsm_name_to_attr(name);
- int rc;
+ int rc = -EINVAL;

if (attr) {
rc = selinux_lsm_getattr(attr, p, value);
- if (rc != -EOPNOTSUPP)
- return rc;
+ if (rc == -EOPNOTSUPP)
+ rc = -EINVAL;
}
-
- return -EINVAL;
+ if (rc < 0)
+ return rc;
+ *len = rc;
+ return 0;
}

static int selinux_setprocattr(const char *name, void *value, size_t size,
diff --git a/security/smack/smack_lsm.c b/security/smack/smack_lsm.c
index 4265f2639106..8a352bd05565 100644
--- a/security/smack/smack_lsm.c
+++ b/security/smack/smack_lsm.c
@@ -3681,16 +3681,17 @@ static int smack_getselfattr(unsigned int attr, struct lsm_ctx __user *ctx,
* @p: the object task
* @name: the name of the attribute in /proc/.../attr
* @value: where to put the result
+ * @len: where to put the length of the result
*
* Places a copy of the task Smack into value
*
- * Returns the length of the smack label or an error code
+ * Returns 0 on success or a negative error code on failure.
*/
-static int smack_getprocattr(struct task_struct *p, const char *name, char **value)
+static int smack_getprocattr(struct task_struct *p, const char *name,
+ char **value, u32 *len)
{
struct smack_known *skp = smk_of_task_struct_obj(p);
char *cp;
- int slen;

if (strcmp(name, "current") != 0)
return -EINVAL;
@@ -3699,9 +3700,9 @@ static int smack_getprocattr(struct task_struct *p, const char *name, char **val
if (cp == NULL)
return -ENOMEM;

- slen = strlen(cp);
+ *len = strlen(cp);
*value = cp;
- return slen;
+ return 0;
}

/**
--
2.30.2