[PATCH v3] mm/memfd: security hook for memfd_create
From: jeffxu
Date: Thu Dec 01 2022 - 20:36:13 EST
From: Jeff Xu <jeffxu@xxxxxxxxxxxx>
The new security_memfd_create allows lsm to check flags of
memfd_create.
The security by default system (such as chromeos) can use this
to implement system wide lsm to allow only non-executable memfd
being created.
Signed-off-by: Jeff Xu <jeffxu@xxxxxxxxxxxx>
---
include/linux/lsm_hook_defs.h | 1 +
include/linux/lsm_hooks.h | 4 ++++
include/linux/security.h | 6 ++++++
mm/memfd.c | 5 +++++
4 files changed, 16 insertions(+)
diff --git a/include/linux/lsm_hook_defs.h b/include/linux/lsm_hook_defs.h
index ec119da1d89b..fd40840927c8 100644
--- a/include/linux/lsm_hook_defs.h
+++ b/include/linux/lsm_hook_defs.h
@@ -164,6 +164,7 @@ LSM_HOOK(int, 0, file_alloc_security, struct file *file)
LSM_HOOK(void, LSM_RET_VOID, file_free_security, struct file *file)
LSM_HOOK(int, 0, file_ioctl, struct file *file, unsigned int cmd,
unsigned long arg)
+LSM_HOOK(int, 0, memfd_create, char *name, unsigned int flags)
LSM_HOOK(int, 0, mmap_addr, unsigned long addr)
LSM_HOOK(int, 0, mmap_file, struct file *file, unsigned long reqprot,
unsigned long prot, unsigned long flags)
diff --git a/include/linux/lsm_hooks.h b/include/linux/lsm_hooks.h
index 4ec80b96c22e..5a18a6552278 100644
--- a/include/linux/lsm_hooks.h
+++ b/include/linux/lsm_hooks.h
@@ -543,6 +543,10 @@
* simple integer value. When @arg represents a user space pointer, it
* should never be used by the security module.
* Return 0 if permission is granted.
+ * @memfd_create:
+ * @name is the name of memfd file.
+ * @flags is the flags used in memfd_create.
+ * Return 0 if permission is granted.
* @mmap_addr :
* Check permissions for a mmap operation at @addr.
* @addr contains virtual address that will be used for the operation.
diff --git a/include/linux/security.h b/include/linux/security.h
index ca1b7109c0db..5b87a780822a 100644
--- a/include/linux/security.h
+++ b/include/linux/security.h
@@ -384,6 +384,7 @@ int security_file_permission(struct file *file, int mask);
int security_file_alloc(struct file *file);
void security_file_free(struct file *file);
int security_file_ioctl(struct file *file, unsigned int cmd, unsigned long arg);
+int security_memfd_create(char *name, unsigned int flags);
int security_mmap_file(struct file *file, unsigned long prot,
unsigned long flags);
int security_mmap_addr(unsigned long addr);
@@ -963,6 +964,11 @@ static inline int security_file_ioctl(struct file *file, unsigned int cmd,
return 0;
}
+static inline int security_memfd_create(char *name, unsigned int flags)
+{
+ return 0;
+}
+
static inline int security_mmap_file(struct file *file, unsigned long prot,
unsigned long flags)
{
diff --git a/mm/memfd.c b/mm/memfd.c
index 69e897dea6d5..96dcfbfed09e 100644
--- a/mm/memfd.c
+++ b/mm/memfd.c
@@ -346,6 +346,11 @@ SYSCALL_DEFINE2(memfd_create,
goto err_name;
}
+ /* security hook for memfd_create */
+ error = security_memfd_create(name, flags);
+ if (error)
+ return error;
+
if (flags & MFD_HUGETLB) {
file = hugetlb_file_setup(name, 0, VM_NORESERVE,
HUGETLB_ANONHUGE_INODE,
--
2.39.0.rc0.267.gcb52ba06e7-goog