[RFC PATCH -mm 1/4] mm, security: Add lsm hook for mbind(2)

[Yafang Shao]

In container environment, we don't want users to bind their memory to a
specific numa node, while we want to unit control memory resource with
kubelet. Therefore, add a new lsm hook for mbind(2), then we can enforce
fine-grained control over memory policy adjustment by the tasks in a
container.

Signed-off-by: Yafang Shao <laoar.shao at gmail.com>
---
 include/linux/lsm_hook_defs.h |  4 ++++
 include/linux/security.h      | 10 ++++++++++
 mm/mempolicy.c                |  4 ++++
 security/security.c           |  7 +++++++
 4 files changed, 25 insertions(+)

diff --git a/include/linux/lsm_hook_defs.h b/include/linux/lsm_hook_defs.h
index 99b8176..b1b5e3a 100644
--- a/include/linux/lsm_hook_defs.h
+++ b/include/linux/lsm_hook_defs.h
@@ -419,3 +419,7 @@
 LSM_HOOK(int, 0, uring_sqpoll, void)
 LSM_HOOK(int, 0, uring_cmd, struct io_uring_cmd *ioucmd)
 #endif /* CONFIG_IO_URING */
+
+LSM_HOOK(int, 0, mbind, unsigned long start, unsigned long len,
+	 unsigned long mode, const unsigned long __user *nmask,
+	 unsigned long maxnode, unsigned int flags)
diff --git a/include/linux/security.h b/include/linux/security.h
index 1d1df326..9f87543 100644
--- a/include/linux/security.h
+++ b/include/linux/security.h
@@ -484,6 +484,9 @@ int security_setprocattr(const char *lsm, const char *name, void *value,
 int security_inode_setsecctx(struct dentry *dentry, void *ctx, u32 ctxlen);
 int security_inode_getsecctx(struct inode *inode, void **ctx, u32 *ctxlen);
 int security_locked_down(enum lockdown_reason what);
+int security_mbind(unsigned long start, unsigned long len,
+		   unsigned long mode, const unsigned long __user *nmask,
+		   unsigned long maxnode, unsigned int flags);
 #else /* CONFIG_SECURITY */
 
 static inline int call_blocking_lsm_notifier(enum lsm_event event, void *data)
@@ -1395,6 +1398,13 @@ static inline int security_locked_down(enum lockdown_reason what)
 {
 	return 0;
 }
+
+static inline int security_mbind(unsigned long start, unsigned long len,
+				 unsigned long mode, const unsigned long __user *nmask,
+				 unsigned long maxnode, unsigned int flags)
+{
+	return 0;
+}
 #endif	/* CONFIG_SECURITY */
 
 #if defined(CONFIG_SECURITY) && defined(CONFIG_WATCH_QUEUE)
diff --git a/mm/mempolicy.c b/mm/mempolicy.c
index 10a590e..98a378c 100644
--- a/mm/mempolicy.c
+++ b/mm/mempolicy.c
@@ -1483,6 +1483,10 @@ static long kernel_mbind(unsigned long start, unsigned long len,
 	if (err)
 		return err;
 
+	err = security_mbind(start, len, mode, nmask, maxnode, flags);
+	if (err)
+		return err;
+
 	return do_mbind(start, len, lmode, mode_flags, &nodes, flags);
 }
 
diff --git a/security/security.c b/security/security.c
index dcb3e70..425ec1c 100644
--- a/security/security.c
+++ b/security/security.c
@@ -5337,3 +5337,10 @@ int security_uring_cmd(struct io_uring_cmd *ioucmd)
 	return call_int_hook(uring_cmd, 0, ioucmd);
 }
 #endif /* CONFIG_IO_URING */
+
+int security_mbind(unsigned long start, unsigned long len,
+		   unsigned long mode, const unsigned long __user *nmask,
+		   unsigned long maxnode, unsigned int flags)
+{
+	return call_int_hook(mbind, 0, start, len, mode, nmask, maxnode, flags);
+}
-- 
1.8.3.1