[PATCH v6 1/5] security: create file_truncate hook from path_truncate hook
John Johansen
john.johansen at canonical.com
Fri Sep 9 03:37:03 UTC 2022
On 9/8/22 12:58, Günther Noack wrote:
> Like path_truncate, the file_truncate hook also restricts file
> truncation, but is called in the cases where truncation is attempted
> on an already-opened file.
>
> This is required in a subsequent commit to handle ftruncate()
> operations differently to truncate() operations.
>
> Signed-off-by: Günther Noack <gnoack3000 at gmail.com>
Acked-by: John Johansen <john.johansen at canonical.com>
> ---
> fs/namei.c | 6 +++---
> fs/open.c | 4 ++--
> include/linux/lsm_hook_defs.h | 1 +
> include/linux/security.h | 6 ++++++
> security/apparmor/lsm.c | 6 ++++++
> security/security.c | 5 +++++
> security/tomoyo/tomoyo.c | 13 +++++++++++++
> 7 files changed, 36 insertions(+), 5 deletions(-)
>
> diff --git a/fs/namei.c b/fs/namei.c
> index 53b4bc094db2..52105873d1f8 100644
> --- a/fs/namei.c
> +++ b/fs/namei.c
> @@ -53,8 +53,8 @@
> * The new code replaces the old recursive symlink resolution with
> * an iterative one (in case of non-nested symlink chains). It does
> * this with calls to <fs>_follow_link().
> - * As a side effect, dir_namei(), _namei() and follow_link() are now
> - * replaced with a single function lookup_dentry() that can handle all
> + * As a side effect, dir_namei(), _namei() and follow_link() are now
> + * replaced with a single function lookup_dentry() that can handle all
> * the special cases of the former code.
> *
> * With the new dcache, the pathname is stored at each inode, at least as
> @@ -3211,7 +3211,7 @@ static int handle_truncate(struct user_namespace *mnt_userns, struct file *filp)
> if (error)
> return error;
>
> - error = security_path_truncate(path);
> + error = security_file_truncate(filp);
> if (!error) {
> error = do_truncate(mnt_userns, path->dentry, 0,
> ATTR_MTIME|ATTR_CTIME|ATTR_OPEN,
> diff --git a/fs/open.c b/fs/open.c
> index 8a813fa5ca56..0831433e493a 100644
> --- a/fs/open.c
> +++ b/fs/open.c
> @@ -188,7 +188,7 @@ long do_sys_ftruncate(unsigned int fd, loff_t length, int small)
> if (IS_APPEND(file_inode(f.file)))
> goto out_putf;
> sb_start_write(inode->i_sb);
> - error = security_path_truncate(&f.file->f_path);
> + error = security_file_truncate(f.file);
> if (!error)
> error = do_truncate(file_mnt_user_ns(f.file), dentry, length,
> ATTR_MTIME | ATTR_CTIME, f.file);
> @@ -1271,7 +1271,7 @@ struct file *filp_open(const char *filename, int flags, umode_t mode)
> {
> struct filename *name = getname_kernel(filename);
> struct file *file = ERR_CAST(name);
> -
> +
> if (!IS_ERR(name)) {
> file = file_open_name(name, flags, mode);
> putname(name);
> diff --git a/include/linux/lsm_hook_defs.h b/include/linux/lsm_hook_defs.h
> index 60fff133c0b1..dee35ab253ba 100644
> --- a/include/linux/lsm_hook_defs.h
> +++ b/include/linux/lsm_hook_defs.h
> @@ -177,6 +177,7 @@ LSM_HOOK(int, 0, file_send_sigiotask, struct task_struct *tsk,
> struct fown_struct *fown, int sig)
> LSM_HOOK(int, 0, file_receive, struct file *file)
> LSM_HOOK(int, 0, file_open, struct file *file)
> +LSM_HOOK(int, 0, file_truncate, struct file *file)
> LSM_HOOK(int, 0, task_alloc, struct task_struct *task,
> unsigned long clone_flags)
> LSM_HOOK(void, LSM_RET_VOID, task_free, struct task_struct *task)
> diff --git a/include/linux/security.h b/include/linux/security.h
> index 7bd0c490703d..f80b23382dd9 100644
> --- a/include/linux/security.h
> +++ b/include/linux/security.h
> @@ -394,6 +394,7 @@ int security_file_send_sigiotask(struct task_struct *tsk,
> struct fown_struct *fown, int sig);
> int security_file_receive(struct file *file);
> int security_file_open(struct file *file);
> +int security_file_truncate(struct file *file);
> int security_task_alloc(struct task_struct *task, unsigned long clone_flags);
> void security_task_free(struct task_struct *task);
> int security_cred_alloc_blank(struct cred *cred, gfp_t gfp);
> @@ -1011,6 +1012,11 @@ static inline int security_file_open(struct file *file)
> return 0;
> }
>
> +static inline int security_file_truncate(struct file *file)
> +{
> + return 0;
> +}
> +
> static inline int security_task_alloc(struct task_struct *task,
> unsigned long clone_flags)
> {
> diff --git a/security/apparmor/lsm.c b/security/apparmor/lsm.c
> index e29cade7b662..98ecb7f221b8 100644
> --- a/security/apparmor/lsm.c
> +++ b/security/apparmor/lsm.c
> @@ -329,6 +329,11 @@ static int apparmor_path_truncate(const struct path *path)
> return common_perm_cond(OP_TRUNC, path, MAY_WRITE | AA_MAY_SETATTR);
> }
>
> +static int apparmor_file_truncate(struct file *file)
> +{
> + return apparmor_path_truncate(&file->f_path);
> +}
> +
> static int apparmor_path_symlink(const struct path *dir, struct dentry *dentry,
> const char *old_name)
> {
> @@ -1232,6 +1237,7 @@ static struct security_hook_list apparmor_hooks[] __lsm_ro_after_init = {
> LSM_HOOK_INIT(mmap_file, apparmor_mmap_file),
> LSM_HOOK_INIT(file_mprotect, apparmor_file_mprotect),
> LSM_HOOK_INIT(file_lock, apparmor_file_lock),
> + LSM_HOOK_INIT(file_truncate, apparmor_file_truncate),
>
> LSM_HOOK_INIT(getprocattr, apparmor_getprocattr),
> LSM_HOOK_INIT(setprocattr, apparmor_setprocattr),
> diff --git a/security/security.c b/security/security.c
> index 4b95de24bc8d..e491120c48ba 100644
> --- a/security/security.c
> +++ b/security/security.c
> @@ -1210,6 +1210,11 @@ int security_path_truncate(const struct path *path)
> return call_int_hook(path_truncate, 0, path);
> }
>
> +int security_file_truncate(struct file *file)
> +{
> + return call_int_hook(file_truncate, 0, file);
> +}
> +
> int security_path_chmod(const struct path *path, umode_t mode)
> {
> if (unlikely(IS_PRIVATE(d_backing_inode(path->dentry))))
> diff --git a/security/tomoyo/tomoyo.c b/security/tomoyo/tomoyo.c
> index 71e82d855ebf..af04a7b7eb28 100644
> --- a/security/tomoyo/tomoyo.c
> +++ b/security/tomoyo/tomoyo.c
> @@ -134,6 +134,18 @@ static int tomoyo_path_truncate(const struct path *path)
> return tomoyo_path_perm(TOMOYO_TYPE_TRUNCATE, path, NULL);
> }
>
> +/**
> + * tomoyo_file_truncate - Target for security_file_truncate().
> + *
> + * @file: Pointer to "struct file".
> + *
> + * Returns 0 on success, negative value otherwise.
> + */
> +static int tomoyo_file_truncate(struct file *file)
> +{
> + return tomoyo_path_truncate(&file->f_path);
> +}
> +
> /**
> * tomoyo_path_unlink - Target for security_path_unlink().
> *
> @@ -545,6 +557,7 @@ static struct security_hook_list tomoyo_hooks[] __lsm_ro_after_init = {
> LSM_HOOK_INIT(bprm_check_security, tomoyo_bprm_check_security),
> LSM_HOOK_INIT(file_fcntl, tomoyo_file_fcntl),
> LSM_HOOK_INIT(file_open, tomoyo_file_open),
> + LSM_HOOK_INIT(file_truncate, tomoyo_file_truncate),
> LSM_HOOK_INIT(path_truncate, tomoyo_path_truncate),
> LSM_HOOK_INIT(path_unlink, tomoyo_path_unlink),
> LSM_HOOK_INIT(path_mkdir, tomoyo_path_mkdir),
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