[PATCH bpf-next v4 01/20] lsm: Refactor return value of LSM hook vm_enough_memory

Xu Kuohai
2024-07-11T11:14:05Z

From: Xu Kuohai <xukuohai@huawei.com>

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

Before:
- Hook vm_enough_memory returns 1 if permission is granted, 0 if not.
- LSM_RET_DEFAULT(vm_enough_memory_mm) is 1.

After:
- Hook vm_enough_memory reutrns 0 if permission is granted, negative
error code if not.
- LSM_RET_DEFAULT(vm_enough_memory_mm) is 0.

Signed-off-by: Xu Kuohai <xukuohai@huawei.com>
---
include/linux/lsm_hook_defs.h | 2 +-
include/linux/security.h | 2 +-
security/commoncap.c | 11 +++--------
security/security.c | 11 +++++------
security/selinux/hooks.c | 15 ++++-----------
5 files changed, 14 insertions(+), 27 deletions(-)

diff --git a/include/linux/lsm_hook_defs.h b/include/linux/lsm_hook_defs.h
index 44488b1ab9a9..e6e6f8473955 100644
--- a/include/linux/lsm_hook_defs.h
+++ b/include/linux/lsm_hook_defs.h
@@ -48,7 +48,7 @@ LSM_HOOK(int, 0, quota_on, struct dentry *dentry)
LSM_HOOK(int, 0, syslog, int type)
LSM_HOOK(int, 0, settime, const struct timespec64 *ts,
const struct timezone *tz)
-LSM_HOOK(int, 1, vm_enough_memory, struct mm_struct *mm, long pages)
+LSM_HOOK(int, 0, vm_enough_memory, struct mm_struct *mm, long pages)
LSM_HOOK(int, 0, bprm_creds_for_exec, struct linux_binprm *bprm)
LSM_HOOK(int, 0, bprm_creds_from_file, struct linux_binprm *bprm, const struct file *file)
LSM_HOOK(int, 0, bprm_check_security, struct linux_binprm *bprm)
diff --git a/include/linux/security.h b/include/linux/security.h
index de3af33e6ff5..454f96307cb9 100644
--- a/include/linux/security.h
+++ b/include/linux/security.h
@@ -634,7 +634,7 @@ static inline int security_settime64(const struct timespec64 *ts,

static inline int security_vm_enough_memory_mm(struct mm_struct *mm, long pages)
{
- return __vm_enough_memory(mm, pages, cap_vm_enough_memory(mm, pages));
+ return __vm_enough_memory(mm, pages, !cap_vm_enough_memory(mm, pages));
}

static inline int security_bprm_creds_for_exec(struct linux_binprm *bprm)
diff --git a/security/commoncap.c b/security/commoncap.c
index 162d96b3a676..cefad323a0b1 100644
--- a/security/commoncap.c
+++ b/security/commoncap.c
@@ -1396,17 +1396,12 @@ int cap_task_prctl(int option, unsigned long arg2, unsigned long arg3,
* Determine whether the allocation of a new virtual mapping by the current
* task is permitted.
*
- * Return: 1 if permission is granted, 0 if not.
+ * Return: 0 if permission granted, negative error code if not.
*/
int cap_vm_enough_memory(struct mm_struct *mm, long pages)
{
- int cap_sys_admin = 0;
-
- if (cap_capable(current_cred(), &init_user_ns,
- CAP_SYS_ADMIN, CAP_OPT_NOAUDIT) == 0)
- cap_sys_admin = 1;
-
- return cap_sys_admin;
+ return cap_capable(current_cred(), &init_user_ns, CAP_SYS_ADMIN,
+ CAP_OPT_NOAUDIT);
}

/**
diff --git a/security/security.c b/security/security.c
index e5ca08789f74..3475f0cab3da 100644
--- a/security/security.c
+++ b/security/security.c
@@ -1115,15 +1115,14 @@ int security_vm_enough_memory_mm(struct mm_struct *mm, long pages)
int rc;

/*
- * The module will respond with a positive value if
- * it thinks the __vm_enough_memory() call should be
- * made with the cap_sys_admin set. If all of the modules
- * agree that it should be set it will. If any module
- * thinks it should not be set it won't.
+ * The module will respond with 0 if it thinks the __vm_enough_memory()
+ * call should be made with the cap_sys_admin set. If all of the modules
+ * agree that it should be set it will. If any module thinks it should
+ * not be set it won't.
*/
hlist_for_each_entry(hp, &security_hook_heads.vm_enough_memory, list) {
rc = hp->hook.vm_enough_memory(mm, pages);
- if (rc <= 0) {
+ if (rc < 0) {
cap_sys_admin = 0;
break;
}
diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c
index 7eed331e90f0..9cd5a8f1f6a3 100644
--- a/security/selinux/hooks.c
+++ b/security/selinux/hooks.c
@@ -2202,23 +2202,16 @@ static int selinux_syslog(int type)
}

/*
- * Check that a process has enough memory to allocate a new virtual
- * mapping. 0 means there is enough memory for the allocation to
- * succeed and -ENOMEM implies there is not.
+ * Check permission for allocating a new virtual mapping. Returns
+ * 0 if permission is granted, negative error code if not.
*
* Do not audit the selinux permission check, as this is applied to all
* processes that allocate mappings.
*/
static int selinux_vm_enough_memory(struct mm_struct *mm, long pages)
{
- int rc, cap_sys_admin = 0;
-
- rc = cred_has_capability(current_cred(), CAP_SYS_ADMIN,
- CAP_OPT_NOAUDIT, true);
- if (rc == 0)
- cap_sys_admin = 1;
-
- return cap_sys_admin;
+ return cred_has_capability(current_cred(), CAP_SYS_ADMIN,
+ CAP_OPT_NOAUDIT, true);
}

/* binprm security operations */
--
2.30.2