Re: [PATCH v6 1/5] security: create file_truncate hook from path_truncate hook

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Great! Just the unintended hunks to remove as pointed by Paul.


On 08/09/2022 21:58, 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@xxxxxxxxx>
---
  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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