diff mbox series

[v9,17/25] security: Introduce inode_post_remove_acl hook

Message ID 20240115181809.885385-18-roberto.sassu@huaweicloud.com (mailing list archive)
State Accepted
Commit 2d705d8024143c272a764320c880ccd3230bb699
Headers show
Series security: Move IMA and EVM to the LSM infrastructure | expand

Commit Message

Roberto Sassu Jan. 15, 2024, 6:18 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.

At inode_remove_acl hook, EVM verifies the file's existing HMAC value. At
inode_post_remove_acl, EVM re-calculates the file's HMAC with the passed
POSIX ACL removed and other file metadata.

Other LSMs could similarly take some action after successful POSIX ACL
removal.

The new hook cannot return an error and cannot cause the operation to be
reverted.

Signed-off-by: Roberto Sassu <roberto.sassu@huawei.com>
Reviewed-by: Stefan Berger <stefanb@linux.ibm.com>
Acked-by: Casey Schaufler <casey@schaufler-ca.com>
Reviewed-by: Mimi Zohar <zohar@linux.ibm.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

Paul Moore Feb. 8, 2024, 3:18 a.m. UTC | #1
On Jan 15, 2024 Roberto Sassu <roberto.sassu@huaweicloud.com> wrote:
> 
> In preparation for moving IMA and EVM to the LSM infrastructure, introduce
> the inode_post_remove_acl hook.
> 
> At inode_remove_acl hook, EVM verifies the file's existing HMAC value. At
> inode_post_remove_acl, EVM re-calculates the file's HMAC with the passed
> POSIX ACL removed and other file metadata.
> 
> Other LSMs could similarly take some action after successful POSIX ACL
> removal.
> 
> The new hook cannot return an error and cannot cause the operation to be
> reverted.
> 
> Signed-off-by: Roberto Sassu <roberto.sassu@huawei.com>
> Reviewed-by: Stefan Berger <stefanb@linux.ibm.com>
> Acked-by: Casey Schaufler <casey@schaufler-ca.com>
> Reviewed-by: Mimi Zohar <zohar@linux.ibm.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(+)

Acked-by: Paul Moore <paul@paul-moore.com>

--
paul-moore.com
Christian Brauner Feb. 9, 2024, 9:52 a.m. UTC | #2
On Mon, Jan 15, 2024 at 07:18:01PM +0100, 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.
> 
> At inode_remove_acl hook, EVM verifies the file's existing HMAC value. At
> inode_post_remove_acl, EVM re-calculates the file's HMAC with the passed
> POSIX ACL removed and other file metadata.
> 
> Other LSMs could similarly take some action after successful POSIX ACL
> removal.
> 
> The new hook cannot return an error and cannot cause the operation to be
> reverted.
> 
> Signed-off-by: Roberto Sassu <roberto.sassu@huawei.com>
> Reviewed-by: Stefan Berger <stefanb@linux.ibm.com>
> Acked-by: Casey Schaufler <casey@schaufler-ca.com>
> Reviewed-by: Mimi Zohar <zohar@linux.ibm.com>
> ---
>  fs/posix_acl.c                |  1 +

Acked-by: Christian Brauner <brauner@kernel.org>
diff mbox series

Patch

diff --git a/fs/posix_acl.c b/fs/posix_acl.c
index 58e3c1e2fbbc..e3fbe1a9f3f5 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 e1a9a4e0760c..47dc633090a4 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 c372797e1617..4b03c76b91f1 100644
--- a/include/linux/security.h
+++ b/include/linux/security.h
@@ -378,6 +378,9 @@  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);
@@ -936,6 +939,11 @@  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 82da3667c4ae..617acfaa44d1 100644
--- a/security/security.c
+++ b/security/security.c
@@ -2413,6 +2413,23 @@  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 security after rm posix acls
+ * @idmap: idmap of the mount
+ * @dentry: file
+ * @acl_name: acl name
+ *
+ * Update inode security data after successfully removing posix acls 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