Re: [PATCH (for 3.15) 1/5] LSM: Pass the rename flags to each LSM module.

[Casey Schaufler]

On 4/24/2014 4:22 AM, Tetsuo Handa wrote:
> >From 207346b4153e2b441e0c45d933043e6ba7abb419 Mon Sep 17 00:00:00 2001
> From: Tetsuo Handa <penguin-kernel@xxxxxxxxxxxxxxxxxxx>
> Date: Thu, 24 Apr 2014 20:04:57 +0900
> Subject: [PATCH (for 3.15) 1/5] LSM: Pass the rename flags to each LSM module.
>
> Commit da1ce067 "vfs: add cross-rename" changed security_inode_rename() and
> security_path_rename() to call LSM module with reversed arguments if the rename
> flags contain RENAME_EXCHANGE. But that commit introduced a race window for
> TOMOYO and AppArmor (users of security_path_rename) because the pathnames may
> have been changed between the first call and the second call.
>
> To fix this race condition, the rename flags should be passed to LSM module
> in order to allow LSM module to avoid re-calculation of pathnames.
> Passing the rename flags allows SMACK (one of users of security_inode_rename)
> to avoid needlessly checking the same permission twice.
>
> Signed-off-by: Tetsuo Handa <penguin-kernel@xxxxxxxxxxxxxxxxxxx>

Acked-by: Casey Schaufler <casey@xxxxxxxxxxxxxxxx>

At least for the Smack changes.

> ---
>  include/linux/security.h   |    8 ++++++--
>  security/apparmor/lsm.c    |    3 ++-
>  security/capability.c      |    6 ++++--
>  security/security.c        |   10 ++++++----
>  security/selinux/hooks.c   |    3 ++-
>  security/smack/smack_lsm.c |    4 +++-
>  security/tomoyo/tomoyo.c   |    4 +++-
>  7 files changed, 26 insertions(+), 12 deletions(-)
>
> diff --git a/include/linux/security.h b/include/linux/security.h
> index 9c6b972..12770bb 100644
> --- a/include/linux/security.h
> +++ b/include/linux/security.h
> @@ -446,6 +446,7 @@ static inline void security_free_mnt_opts(struct security_mnt_opts *opts)
>   *	@old_dentry contains the dentry structure of the old link.
>   *	@new_dir contains the inode structure for parent of the new link.
>   *	@new_dentry contains the dentry structure of the new link.
> + *	@flags contains rename flags.
>   *	Return 0 if permission is granted.
>   * @path_rename:
>   *	Check for permission to rename a file or directory.
> @@ -453,6 +454,7 @@ static inline void security_free_mnt_opts(struct security_mnt_opts *opts)
>   *	@old_dentry contains the dentry structure of the old link.
>   *	@new_dir contains the path structure for parent of the new link.
>   *	@new_dentry contains the dentry structure of the new link.
> + *	@flags contains rename flags.
>   *	Return 0 if permission is granted.
>   * @path_chmod:
>   *	Check for permission to change DAC's permission of a file or directory.
> @@ -1492,7 +1494,8 @@ struct security_operations {
>  	int (*path_link) (struct dentry *old_dentry, struct path *new_dir,
>  			  struct dentry *new_dentry);
>  	int (*path_rename) (struct path *old_dir, struct dentry *old_dentry,
> -			    struct path *new_dir, struct dentry *new_dentry);
> +			    struct path *new_dir, struct dentry *new_dentry,
> +			    unsigned int flags);
>  	int (*path_chmod) (struct path *path, umode_t mode);
>  	int (*path_chown) (struct path *path, kuid_t uid, kgid_t gid);
>  	int (*path_chroot) (struct path *path);
> @@ -1515,7 +1518,8 @@ struct security_operations {
>  	int (*inode_mknod) (struct inode *dir, struct dentry *dentry,
>  			    umode_t mode, dev_t dev);
>  	int (*inode_rename) (struct inode *old_dir, struct dentry *old_dentry,
> -			     struct inode *new_dir, struct dentry *new_dentry);
> +			     struct inode *new_dir, struct dentry *new_dentry,
> +			     unsigned int flags);
>  	int (*inode_readlink) (struct dentry *dentry);
>  	int (*inode_follow_link) (struct dentry *dentry, struct nameidata *nd);
>  	int (*inode_permission) (struct inode *inode, int mask);
> diff --git a/security/apparmor/lsm.c b/security/apparmor/lsm.c
> index 9981000..c0b4366 100644
> --- a/security/apparmor/lsm.c
> +++ b/security/apparmor/lsm.c
> @@ -315,7 +315,8 @@ static int apparmor_path_link(struct dentry *old_dentry, struct path *new_dir,
>  }
>  
>  static int apparmor_path_rename(struct path *old_dir, struct dentry *old_dentry,
> -				struct path *new_dir, struct dentry *new_dentry)
> +				struct path *new_dir, struct dentry *new_dentry,
> +				unsigned int flags)
>  {
>  	struct aa_profile *profile;
>  	int error = 0;
> diff --git a/security/capability.c b/security/capability.c
> index e76373d..b3690cc 100644
> --- a/security/capability.c
> +++ b/security/capability.c
> @@ -176,7 +176,8 @@ static int cap_inode_mknod(struct inode *inode, struct dentry *dentry,
>  }
>  
>  static int cap_inode_rename(struct inode *old_inode, struct dentry *old_dentry,
> -			    struct inode *new_inode, struct dentry *new_dentry)
> +			    struct inode *new_inode, struct dentry *new_dentry,
> +			    unsigned int flags)
>  {
>  	return 0;
>  }
> @@ -280,7 +281,8 @@ static int cap_path_link(struct dentry *old_dentry, struct path *new_dir,
>  }
>  
>  static int cap_path_rename(struct path *old_path, struct dentry *old_dentry,
> -			   struct path *new_path, struct dentry *new_dentry)
> +			   struct path *new_path, struct dentry *new_dentry,
> +			   unsigned int flags)
>  {
>  	return 0;
>  }
> diff --git a/security/security.c b/security/security.c
> index 31614e9..65ceef3 100644
> --- a/security/security.c
> +++ b/security/security.c
> @@ -442,13 +442,14 @@ int security_path_rename(struct path *old_dir, struct dentry *old_dentry,
>  
>  	if (flags & RENAME_EXCHANGE) {
>  		int err = security_ops->path_rename(new_dir, new_dentry,
> -						    old_dir, old_dentry);
> +						    old_dir, old_dentry,
> +						    flags);
>  		if (err)
>  			return err;
>  	}
>  
>  	return security_ops->path_rename(old_dir, old_dentry, new_dir,
> -					 new_dentry);
> +					 new_dentry, flags);
>  }
>  EXPORT_SYMBOL(security_path_rename);
>  
> @@ -542,13 +543,14 @@ int security_inode_rename(struct inode *old_dir, struct dentry *old_dentry,
>  
>  	if (flags & RENAME_EXCHANGE) {
>  		int err = security_ops->inode_rename(new_dir, new_dentry,
> -						     old_dir, old_dentry);
> +						     old_dir, old_dentry,
> +						     flags);
>  		if (err)
>  			return err;
>  	}
>  
>  	return security_ops->inode_rename(old_dir, old_dentry,
> -					   new_dir, new_dentry);
> +					  new_dir, new_dentry, flags);
>  }
>  
>  int security_inode_readlink(struct dentry *dentry)
> diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c
> index 6befc92..d4913d1 100644
> --- a/security/selinux/hooks.c
> +++ b/security/selinux/hooks.c
> @@ -2749,7 +2749,8 @@ static int selinux_inode_mknod(struct inode *dir, struct dentry *dentry, umode_t
>  }
>  
>  static int selinux_inode_rename(struct inode *old_inode, struct dentry *old_dentry,
> -				struct inode *new_inode, struct dentry *new_dentry)
> +				struct inode *new_inode, struct dentry *new_dentry,
> +				unsigned int flags)
>  {
>  	return may_rename(old_inode, old_dentry, new_inode, new_dentry);
>  }
> diff --git a/security/smack/smack_lsm.c b/security/smack/smack_lsm.c
> index 8177e7d..41bd059 100644
> --- a/security/smack/smack_lsm.c
> +++ b/security/smack/smack_lsm.c
> @@ -697,6 +697,7 @@ static int smack_inode_rmdir(struct inode *dir, struct dentry *dentry)
>   * @old_dentry: unused
>   * @new_inode: the new directory
>   * @new_dentry: unused
> + * @flags: unused
>   *
>   * Read and write access is required on both the old and
>   * new directories.
> @@ -706,7 +707,8 @@ static int smack_inode_rmdir(struct inode *dir, struct dentry *dentry)
>  static int smack_inode_rename(struct inode *old_inode,
>  			      struct dentry *old_dentry,
>  			      struct inode *new_inode,
> -			      struct dentry *new_dentry)
> +			      struct dentry *new_dentry,
> +			      unsigned int flags)
>  {
>  	int rc;
>  	char *isp;
> diff --git a/security/tomoyo/tomoyo.c b/security/tomoyo/tomoyo.c
> index f0b756e..ac7dd97 100644
> --- a/security/tomoyo/tomoyo.c
> +++ b/security/tomoyo/tomoyo.c
> @@ -287,13 +287,15 @@ static int tomoyo_path_link(struct dentry *old_dentry, struct path *new_dir,
>   * @old_dentry: Pointer to "struct dentry".
>   * @new_parent: Pointer to "struct path".
>   * @new_dentry: Pointer to "struct dentry".
> + * @flags:      Rename flags.
>   *
>   * Returns 0 on success, negative value otherwise.
>   */
>  static int tomoyo_path_rename(struct path *old_parent,
>  			      struct dentry *old_dentry,
>  			      struct path *new_parent,
> -			      struct dentry *new_dentry)
> +			      struct dentry *new_dentry,
> +			      unsigned int flags)
>  {
>  	struct path path1 = { old_parent->mnt, old_dentry };
>  	struct path path2 = { new_parent->mnt, new_dentry };

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