diff mbox series

[v3,19/25] security: Introduce inode_post_remove_acl hook

Message ID 20230904133415.1799503-20-roberto.sassu@huaweicloud.com (mailing list archive)
State Superseded
Delegated to: Paul Moore
Headers show
Series security: Move IMA and EVM to the LSM infrastructure | expand

Commit Message

Roberto Sassu Sept. 4, 2023, 1:34 p.m. UTC
From: Roberto Sassu <roberto.sassu@huawei.com>

In preparation for moving IMA and EVM to the LSM infrastructure, introduce
the inode_post_remove_acl hook.

It is useful for EVM to recalculate the HMAC on the remaining POSIX ACLs
and other file metadata, after it verified the HMAC of current file
metadata with the inode_remove_acl hook.

LSMs should use the new hook instead of inode_remove_acl, when they need to
know that the operation was done successfully (not known in
inode_remove_acl). The new hook cannot return an error and cannot cause the
operation to be reverted.

Signed-off-by: Roberto Sassu <roberto.sassu@huawei.com>
---
 fs/posix_acl.c                |  1 +
 include/linux/lsm_hook_defs.h |  2 ++
 include/linux/security.h      |  8 ++++++++
 security/security.c           | 17 +++++++++++++++++
 4 files changed, 28 insertions(+)

Comments

Stefan Berger Sept. 5, 2023, 7:01 p.m. UTC | #1
On 9/4/23 09:34, Roberto Sassu wrote:
> From: Roberto Sassu <roberto.sassu@huawei.com>
>
> In preparation for moving IMA and EVM to the LSM infrastructure, introduce
> the inode_post_remove_acl hook.
>
> It is useful for EVM to recalculate the HMAC on the remaining POSIX ACLs
> and other file metadata, after it verified the HMAC of current file
> metadata with the inode_remove_acl hook.
>
> LSMs should use the new hook instead of inode_remove_acl, when they need to
> know that the operation was done successfully (not known in
> inode_remove_acl). The new hook cannot return an error and cannot cause the
> operation to be reverted.
>
> Signed-off-by: Roberto Sassu <roberto.sassu@huawei.com>
> ---
>   fs/posix_acl.c                |  1 +
>   include/linux/lsm_hook_defs.h |  2 ++
>   include/linux/security.h      |  8 ++++++++
>   security/security.c           | 17 +++++++++++++++++
>   4 files changed, 28 insertions(+)
>
> diff --git a/fs/posix_acl.c b/fs/posix_acl.c
> index 3b7dbea5c3ff..2a2a2750b3e9 100644
> --- a/fs/posix_acl.c
> +++ b/fs/posix_acl.c
> @@ -1246,6 +1246,7 @@ int vfs_remove_acl(struct mnt_idmap *idmap, struct dentry *dentry,
>   		error = -EIO;
>   	if (!error) {
>   		fsnotify_xattr(dentry);
> +		security_inode_post_remove_acl(idmap, dentry, acl_name);
>   		evm_inode_post_remove_acl(idmap, dentry, acl_name);
>   	}
>   
> diff --git a/include/linux/lsm_hook_defs.h b/include/linux/lsm_hook_defs.h
> index bba1fbd97207..eedc26790a07 100644
> --- a/include/linux/lsm_hook_defs.h
> +++ b/include/linux/lsm_hook_defs.h
> @@ -163,6 +163,8 @@ LSM_HOOK(int, 0, inode_get_acl, struct mnt_idmap *idmap,
>   	 struct dentry *dentry, const char *acl_name)
>   LSM_HOOK(int, 0, inode_remove_acl, struct mnt_idmap *idmap,
>   	 struct dentry *dentry, const char *acl_name)
> +LSM_HOOK(void, LSM_RET_VOID, inode_post_remove_acl, struct mnt_idmap *idmap,
> +	 struct dentry *dentry, const char *acl_name)
>   LSM_HOOK(int, 0, inode_need_killpriv, struct dentry *dentry)
>   LSM_HOOK(int, 0, inode_killpriv, struct mnt_idmap *idmap,
>   	 struct dentry *dentry)
> diff --git a/include/linux/security.h b/include/linux/security.h
> index 556d019ebe5c..e543ae80309b 100644
> --- a/include/linux/security.h
> +++ b/include/linux/security.h
> @@ -373,6 +373,9 @@ int security_inode_get_acl(struct mnt_idmap *idmap,
>   			   struct dentry *dentry, const char *acl_name);
>   int security_inode_remove_acl(struct mnt_idmap *idmap,
>   			      struct dentry *dentry, const char *acl_name);
> +void security_inode_post_remove_acl(struct mnt_idmap *idmap,
> +				    struct dentry *dentry,
> +				    const char *acl_name);
>   void security_inode_post_setxattr(struct dentry *dentry, const char *name,
>   				  const void *value, size_t size, int flags);
>   int security_inode_getxattr(struct dentry *dentry, const char *name);
> @@ -915,6 +918,11 @@ static inline int security_inode_remove_acl(struct mnt_idmap *idmap,
>   	return 0;
>   }
>   
> +static inline void security_inode_post_remove_acl(struct mnt_idmap *idmap,
> +						  struct dentry *dentry,
> +						  const char *acl_name)
> +{ }
> +
>   static inline void security_inode_post_setxattr(struct dentry *dentry,
>   		const char *name, const void *value, size_t size, int flags)
>   { }
> diff --git a/security/security.c b/security/security.c
> index aabace9e24d9..554f4925323d 100644
> --- a/security/security.c
> +++ b/security/security.c
> @@ -2323,6 +2323,23 @@ int security_inode_remove_acl(struct mnt_idmap *idmap,
>   	return evm_inode_remove_acl(idmap, dentry, acl_name);
>   }
>   
> +/**
> + * security_inode_post_remove_acl() - Update inode sec after remove_acl op
> + * @idmap: idmap of the mount
> + * @dentry: file
> + * @acl_name: acl name
> + *
> + * Update inode security field after successful remove_acl operation on @dentry
> + * in @idmap. The posix acls are identified by @acl_name.
> + */
> +void security_inode_post_remove_acl(struct mnt_idmap *idmap,
> +				    struct dentry *dentry, const char *acl_name)
> +{
> +	if (unlikely(IS_PRIVATE(d_backing_inode(dentry))))
> +		return;
> +	call_void_hook(inode_post_remove_acl, idmap, dentry, acl_name);
> +}
> +
>   /**
>    * security_inode_post_setxattr() - Update the inode after a setxattr operation
>    * @dentry: file

Reviewed-by: Stefan Berger <stefanb@linux.ibm.com>
diff mbox series

Patch

diff --git a/fs/posix_acl.c b/fs/posix_acl.c
index 3b7dbea5c3ff..2a2a2750b3e9 100644
--- a/fs/posix_acl.c
+++ b/fs/posix_acl.c
@@ -1246,6 +1246,7 @@  int vfs_remove_acl(struct mnt_idmap *idmap, struct dentry *dentry,
 		error = -EIO;
 	if (!error) {
 		fsnotify_xattr(dentry);
+		security_inode_post_remove_acl(idmap, dentry, acl_name);
 		evm_inode_post_remove_acl(idmap, dentry, acl_name);
 	}
 
diff --git a/include/linux/lsm_hook_defs.h b/include/linux/lsm_hook_defs.h
index bba1fbd97207..eedc26790a07 100644
--- a/include/linux/lsm_hook_defs.h
+++ b/include/linux/lsm_hook_defs.h
@@ -163,6 +163,8 @@  LSM_HOOK(int, 0, inode_get_acl, struct mnt_idmap *idmap,
 	 struct dentry *dentry, const char *acl_name)
 LSM_HOOK(int, 0, inode_remove_acl, struct mnt_idmap *idmap,
 	 struct dentry *dentry, const char *acl_name)
+LSM_HOOK(void, LSM_RET_VOID, inode_post_remove_acl, struct mnt_idmap *idmap,
+	 struct dentry *dentry, const char *acl_name)
 LSM_HOOK(int, 0, inode_need_killpriv, struct dentry *dentry)
 LSM_HOOK(int, 0, inode_killpriv, struct mnt_idmap *idmap,
 	 struct dentry *dentry)
diff --git a/include/linux/security.h b/include/linux/security.h
index 556d019ebe5c..e543ae80309b 100644
--- a/include/linux/security.h
+++ b/include/linux/security.h
@@ -373,6 +373,9 @@  int security_inode_get_acl(struct mnt_idmap *idmap,
 			   struct dentry *dentry, const char *acl_name);
 int security_inode_remove_acl(struct mnt_idmap *idmap,
 			      struct dentry *dentry, const char *acl_name);
+void security_inode_post_remove_acl(struct mnt_idmap *idmap,
+				    struct dentry *dentry,
+				    const char *acl_name);
 void security_inode_post_setxattr(struct dentry *dentry, const char *name,
 				  const void *value, size_t size, int flags);
 int security_inode_getxattr(struct dentry *dentry, const char *name);
@@ -915,6 +918,11 @@  static inline int security_inode_remove_acl(struct mnt_idmap *idmap,
 	return 0;
 }
 
+static inline void security_inode_post_remove_acl(struct mnt_idmap *idmap,
+						  struct dentry *dentry,
+						  const char *acl_name)
+{ }
+
 static inline void security_inode_post_setxattr(struct dentry *dentry,
 		const char *name, const void *value, size_t size, int flags)
 { }
diff --git a/security/security.c b/security/security.c
index aabace9e24d9..554f4925323d 100644
--- a/security/security.c
+++ b/security/security.c
@@ -2323,6 +2323,23 @@  int security_inode_remove_acl(struct mnt_idmap *idmap,
 	return evm_inode_remove_acl(idmap, dentry, acl_name);
 }
 
+/**
+ * security_inode_post_remove_acl() - Update inode sec after remove_acl op
+ * @idmap: idmap of the mount
+ * @dentry: file
+ * @acl_name: acl name
+ *
+ * Update inode security field after successful remove_acl operation on @dentry
+ * in @idmap. The posix acls are identified by @acl_name.
+ */
+void security_inode_post_remove_acl(struct mnt_idmap *idmap,
+				    struct dentry *dentry, const char *acl_name)
+{
+	if (unlikely(IS_PRIVATE(d_backing_inode(dentry))))
+		return;
+	call_void_hook(inode_post_remove_acl, idmap, dentry, acl_name);
+}
+
 /**
  * security_inode_post_setxattr() - Update the inode after a setxattr operation
  * @dentry: file