On Wed, Dec 07, 2022 at 03:49:39PM +0000, jeffxu@xxxxxxxxxxxx wrote:
> From: Jeff Xu <jeffxu@xxxxxxxxxx>
>
> 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@xxxxxxxxxx>
> Reported-by: kernel test robot <lkp@xxxxxxxxx>
Oh, btw, please CC linux-security-module@xxxxxxxxxxxxxxx when adding new
hooks. (I've added the CC here.)
-Kees
> ---
> include/linux/lsm_hook_defs.h | 1 +
> include/linux/lsm_hooks.h | 4 ++++
> include/linux/security.h | 6 ++++++
> mm/memfd.c | 5 +++++
> security/security.c | 13 +++++++++++++
> 5 files changed, 29 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 92f0a5765f7c..f04ed5f0474f 100644
> --- a/mm/memfd.c
> +++ b/mm/memfd.c
> @@ -356,6 +356,11 @@ 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,
> diff --git a/security/security.c b/security/security.c
> index 79d82cb6e469..5c018e080923 100644
> --- a/security/security.c
> +++ b/security/security.c
> @@ -1010,6 +1010,19 @@ int security_sb_clone_mnt_opts(const struct super_block *oldsb,
> }
> EXPORT_SYMBOL(security_sb_clone_mnt_opts);
>
> +int security_add_mnt_opt(const char *option, const char *val, int len,
> + void **mnt_opts)
> +{
> + return call_int_hook(sb_add_mnt_opt, -EINVAL,
> + option, val, len, mnt_opts);
> +}
> +EXPORT_SYMBOL(security_add_mnt_opt);
> +
> +int security_memfd_create(char *name, unsigned int flags)
> +{
> + return call_int_hook(memfd_create, 0, name, flags);
> +}
> +
> int security_move_mount(const struct path *from_path, const struct path *to_path)
> {
> return call_int_hook(move_mount, 0, from_path, to_path);
> --
> 2.39.0.rc0.267.gcb52ba06e7-goog
>
--
Kees Cook
