Re: [PATCH v3 08/22] vfs: define kernel_read_file_id enumeration

[Kees Cook <keescook@chromium.org>]

On Wed, Feb 3, 2016 at 11:06 AM, Mimi Zohar <zohar@linux.vnet.ibm.com> wrote:
> To differentiate between the kernel_read_file() callers, this patch
> defines a new enumeration named kernel_read_file_id and includes the
> caller identifier as an argument.
>
> Subsequent patches define READING_KEXEC_IMAGE, READING_KEXEC_INITRAMFS,
> READING_FIRMWARE, READING_MODULE, and READING_POLICY.
>
> Changelog v3:
> - Replace the IMA specific enumeration with a generic one.
>
> Signed-off-by: Mimi Zohar <zohar@linux.vnet.ibm.com>

Acked-by: Kees Cook <keescook@chromium.org>

-Kees

> ---
>  fs/exec.c                 | 4 ++--
>  include/linux/fs.h        | 7 ++++++-
>  include/linux/lsm_hooks.h | 4 +++-
>  include/linux/security.h  | 7 +++++--
>  security/security.c       | 5 +++--
>  5 files changed, 19 insertions(+), 8 deletions(-)
>
> diff --git a/fs/exec.c b/fs/exec.c
> index 742de7a..cd2b5b2 100644
> --- a/fs/exec.c
> +++ b/fs/exec.c
> @@ -833,7 +833,7 @@ int kernel_read(struct file *file, loff_t offset,
>  EXPORT_SYMBOL(kernel_read);
>
>  int kernel_read_file(struct file *file, void **buf, loff_t *size,
> -                    loff_t max_size)
> +                    loff_t max_size, enum kernel_read_file_id id)
>  {
>         loff_t i_size, pos;
>         ssize_t bytes = 0;
> @@ -871,7 +871,7 @@ int kernel_read_file(struct file *file, void **buf, loff_t *size,
>                 goto out;
>         }
>
> -       ret = security_kernel_post_read_file(file, *buf, i_size);
> +       ret = security_kernel_post_read_file(file, *buf, i_size, id);
>         if (!ret)
>                 *size = pos;
>
> diff --git a/include/linux/fs.h b/include/linux/fs.h
> index 93ca379..1458ca5 100644
> --- a/include/linux/fs.h
> +++ b/include/linux/fs.h
> @@ -2526,8 +2526,13 @@ static inline void i_readcount_inc(struct inode *inode)
>  #endif
>  extern int do_pipe_flags(int *, int);
>
> +enum kernel_read_file_id {
> +       READING_MAX_ID
> +};
> +
>  extern int kernel_read(struct file *, loff_t, char *, unsigned long);
> -extern int kernel_read_file(struct file *, void **, loff_t *, loff_t);
> +extern int kernel_read_file(struct file *, void **, loff_t *, loff_t,
> +                           enum kernel_read_file_id);
>  extern ssize_t kernel_write(struct file *, const char *, size_t, loff_t);
>  extern ssize_t __kernel_write(struct file *, const char *, size_t, loff_t *);
>  extern struct file * open_exec(const char *);
> diff --git a/include/linux/lsm_hooks.h b/include/linux/lsm_hooks.h
> index f82631c..2337f33 100644
> --- a/include/linux/lsm_hooks.h
> +++ b/include/linux/lsm_hooks.h
> @@ -567,6 +567,7 @@
>   *     by the kernel.
>   *     @buf pointer to buffer containing the file contents.
>   *     @size length of the file contents.
> + *     @id kernel read file identifier
>   *     Return 0 if permission is granted.
>   * @task_fix_setuid:
>   *     Update the module's state after setting one or more of the user
> @@ -1464,7 +1465,8 @@ union security_list_options {
>         int (*kernel_fw_from_file)(struct file *file, char *buf, size_t size);
>         int (*kernel_module_request)(char *kmod_name);
>         int (*kernel_module_from_file)(struct file *file);
> -       int (*kernel_post_read_file)(struct file *file, char *buf, loff_t size);
> +       int (*kernel_post_read_file)(struct file *file, char *buf, loff_t size,
> +                                    enum kernel_read_file_id id);
>         int (*task_fix_setuid)(struct cred *new, const struct cred *old,
>                                 int flags);
>         int (*task_setpgid)(struct task_struct *p, pid_t pgid);
> diff --git a/include/linux/security.h b/include/linux/security.h
> index f30f564..b68ce94 100644
> --- a/include/linux/security.h
> +++ b/include/linux/security.h
> @@ -28,6 +28,7 @@
>  #include <linux/err.h>
>  #include <linux/string.h>
>  #include <linux/mm.h>
> +#include <linux/fs.h>
>
>  struct linux_binprm;
>  struct cred;
> @@ -301,7 +302,8 @@ int security_kernel_create_files_as(struct cred *new, struct inode *inode);
>  int security_kernel_fw_from_file(struct file *file, char *buf, size_t size);
>  int security_kernel_module_request(char *kmod_name);
>  int security_kernel_module_from_file(struct file *file);
> -int security_kernel_post_read_file(struct file *file, char *buf, loff_t size);
> +int security_kernel_post_read_file(struct file *file, char *buf, loff_t size,
> +                                  enum kernel_read_file_id id);
>  int security_task_fix_setuid(struct cred *new, const struct cred *old,
>                              int flags);
>  int security_task_setpgid(struct task_struct *p, pid_t pgid);
> @@ -868,7 +870,8 @@ static inline int security_kernel_module_from_file(struct file *file)
>  }
>
>  static inline int security_kernel_post_read_file(struct file *file,
> -                                                char *buf, loff_t size)
> +                                                char *buf, loff_t size,
> +                                                enum kernel_read_file_id id)
>  {
>         return 0;
>  }
> diff --git a/security/security.c b/security/security.c
> index ae50730..796a261 100644
> --- a/security/security.c
> +++ b/security/security.c
> @@ -910,9 +910,10 @@ int security_kernel_module_from_file(struct file *file)
>         return ima_module_check(file);
>  }
>
> -int security_kernel_post_read_file(struct file *file, char *buf, loff_t size)
> +int security_kernel_post_read_file(struct file *file, char *buf, loff_t size,
> +                                  enum kernel_read_file_id id)
>  {
> -       return call_int_hook(kernel_post_read_file, 0, file, buf, size);
> +       return call_int_hook(kernel_post_read_file, 0, file, buf, size, id);
>  }
>
>  int security_task_fix_setuid(struct cred *new, const struct cred *old,
> --
> 2.1.0
>



-- 
Kees Cook
Chrome OS & Brillo Security