[PATCH 1/5] security: allow finer granularity in permitting copy-up of security xattrs

From: Stefan Berger <stefanb@linux.ibm.com>
To: linux-integrity@vger.kernel.org,
	linux-security-module@vger.kernel.org,
	linux-unionfs@vger.kernel.org
Cc: linux-kernel@vger.kernel.org, paul@paul-moore.com,
	jmorris@namei.org, serge@hallyn.com, zohar@linux.ibm.com,
	roberto.sassu@huawei.com, amir73il@gmail.com, miklos@szeredi.hu,
	Stefan Berger <stefanb@linux.ibm.com>
Subject: [PATCH 1/5] security: allow finer granularity in permitting copy-up of security xattrs
Date: Tue, 30 Jan 2024 16:46:16 -0500	[thread overview]
Message-ID: <20240130214620.3155380-2-stefanb@linux.ibm.com> (raw)
In-Reply-To: <20240130214620.3155380-1-stefanb@linux.ibm.com>

Copying up xattrs is solely based on the security xattr name. For finer
granularity add a dentry parameter to the security_inode_copy_up_xattr
hook definition, allowing decisions to be based on the xattr content as
well.

Signed-off-by: Stefan Berger <stefanb@linux.ibm.com>
---
 fs/overlayfs/copy_up.c            | 2 +-
 include/linux/evm.h               | 2 +-
 include/linux/lsm_hook_defs.h     | 3 ++-
 include/linux/security.h          | 4 ++--
 security/integrity/evm/evm_main.c | 2 +-
 security/security.c               | 7 ++++---
 security/selinux/hooks.c          | 2 +-
 security/smack/smack_lsm.c        | 2 +-
 8 files changed, 13 insertions(+), 11 deletions(-)

diff --git a/fs/overlayfs/copy_up.c b/fs/overlayfs/copy_up.c
index b8e25ca51016..bd9ddcefb7a7 100644
--- a/fs/overlayfs/copy_up.c
+++ b/fs/overlayfs/copy_up.c
@@ -114,7 +114,7 @@ int ovl_copy_xattr(struct super_block *sb, const struct path *oldpath, struct de
 		if (ovl_is_private_xattr(sb, name))
 			continue;
 
-		error = security_inode_copy_up_xattr(name);
+		error = security_inode_copy_up_xattr(old, name);
 		if (error < 0 && error != -EOPNOTSUPP)
 			break;
 		if (error == 1) {
diff --git a/include/linux/evm.h b/include/linux/evm.h
index 36ec884320d9..d8c0343436b8 100644
--- a/include/linux/evm.h
+++ b/include/linux/evm.h
@@ -31,7 +31,7 @@ extern void evm_inode_post_setxattr(struct dentry *dentry,
 				    const char *xattr_name,
 				    const void *xattr_value,
 				    size_t xattr_value_len);
-extern int evm_inode_copy_up_xattr(const char *name);
+extern int evm_inode_copy_up_xattr(struct dentry *dentry, const char *name);
 extern int evm_inode_removexattr(struct mnt_idmap *idmap,
 				 struct dentry *dentry, const char *xattr_name);
 extern void evm_inode_post_removexattr(struct dentry *dentry,
diff --git a/include/linux/lsm_hook_defs.h b/include/linux/lsm_hook_defs.h
index 185924c56378..7dd61f51d84a 100644
--- a/include/linux/lsm_hook_defs.h
+++ b/include/linux/lsm_hook_defs.h
@@ -163,7 +163,8 @@ LSM_HOOK(int, 0, inode_listsecurity, struct inode *inode, char *buffer,
 	 size_t buffer_size)
 LSM_HOOK(void, LSM_RET_VOID, inode_getsecid, struct inode *inode, u32 *secid)
 LSM_HOOK(int, 0, inode_copy_up, struct dentry *src, struct cred **new)
-LSM_HOOK(int, -EOPNOTSUPP, inode_copy_up_xattr, const char *name)
+LSM_HOOK(int, -EOPNOTSUPP, inode_copy_up_xattr, struct dentry *src,
+	 const char *name)
 LSM_HOOK(int, 0, kernfs_init_security, struct kernfs_node *kn_dir,
 	 struct kernfs_node *kn)
 LSM_HOOK(int, 0, file_permission, struct file *file, int mask)
diff --git a/include/linux/security.h b/include/linux/security.h
index d0eb20f90b26..9fc9ca6284d6 100644
--- a/include/linux/security.h
+++ b/include/linux/security.h
@@ -387,7 +387,7 @@ int security_inode_setsecurity(struct inode *inode, const char *name, const void
 int security_inode_listsecurity(struct inode *inode, char *buffer, size_t buffer_size);
 void security_inode_getsecid(struct inode *inode, u32 *secid);
 int security_inode_copy_up(struct dentry *src, struct cred **new);
-int security_inode_copy_up_xattr(const char *name);
+int security_inode_copy_up_xattr(struct dentry *src, const char *name);
 int security_kernfs_init_security(struct kernfs_node *kn_dir,
 				  struct kernfs_node *kn);
 int security_file_permission(struct file *file, int mask);
@@ -980,7 +980,7 @@ static inline int security_kernfs_init_security(struct kernfs_node *kn_dir,
 	return 0;
 }
 
-static inline int security_inode_copy_up_xattr(const char *name)
+static inline int security_inode_copy_up_xattr(struct dentry *src, const char *name)
 {
 	return -EOPNOTSUPP;
 }
diff --git a/security/integrity/evm/evm_main.c b/security/integrity/evm/evm_main.c
index cc7956d7878b..2555aa4501ae 100644
--- a/security/integrity/evm/evm_main.c
+++ b/security/integrity/evm/evm_main.c
@@ -896,7 +896,7 @@ void evm_inode_post_setattr(struct dentry *dentry, int ia_valid)
 		evm_update_evmxattr(dentry, NULL, NULL, 0);
 }
 
-int evm_inode_copy_up_xattr(const char *name)
+int evm_inode_copy_up_xattr(struct dentry *src, const char *name)
 {
 	if (strcmp(name, XATTR_NAME_EVM) == 0)
 		return 1; /* Discard */
diff --git a/security/security.c b/security/security.c
index 0144a98d3712..ee63863c1dc0 100644
--- a/security/security.c
+++ b/security/security.c
@@ -2596,6 +2596,7 @@ EXPORT_SYMBOL(security_inode_copy_up);
 
 /**
  * security_inode_copy_up_xattr() - Filter xattrs in an overlayfs copy-up op
+ * @src: union dentry of copy-up file
  * @name: xattr name
  *
  * Filter the xattrs being copied up when a unioned file is copied up from a
@@ -2606,7 +2607,7 @@ EXPORT_SYMBOL(security_inode_copy_up);
  *         if the security module does not know about attribute, or a negative
  *         error code to abort the copy up.
  */
-int security_inode_copy_up_xattr(const char *name)
+int security_inode_copy_up_xattr(struct dentry *src, const char *name)
 {
 	struct security_hook_list *hp;
 	int rc;
@@ -2618,12 +2619,12 @@ int security_inode_copy_up_xattr(const char *name)
 	 */
 	hlist_for_each_entry(hp,
 			     &security_hook_heads.inode_copy_up_xattr, list) {
-		rc = hp->hook.inode_copy_up_xattr(name);
+		rc = hp->hook.inode_copy_up_xattr(src, name);
 		if (rc != LSM_RET_DEFAULT(inode_copy_up_xattr))
 			return rc;
 	}
 
-	return evm_inode_copy_up_xattr(name);
+	return evm_inode_copy_up_xattr(src, name);
 }
 EXPORT_SYMBOL(security_inode_copy_up_xattr);
 
diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c
index a6bf90ace84c..ebb8876837c6 100644
--- a/security/selinux/hooks.c
+++ b/security/selinux/hooks.c
@@ -3530,7 +3530,7 @@ static int selinux_inode_copy_up(struct dentry *src, struct cred **new)
 	return 0;
 }
 
-static int selinux_inode_copy_up_xattr(const char *name)
+static int selinux_inode_copy_up_xattr(struct dentry *dentry, const char *name)
 {
 	/* The copy_up hook above sets the initial context on an inode, but we
 	 * don't then want to overwrite it by blindly copying all the lower
diff --git a/security/smack/smack_lsm.c b/security/smack/smack_lsm.c
index 0fdbf04cc258..bffca165f07f 100644
--- a/security/smack/smack_lsm.c
+++ b/security/smack/smack_lsm.c
@@ -4873,7 +4873,7 @@ static int smack_inode_copy_up(struct dentry *dentry, struct cred **new)
 	return 0;
 }
 
-static int smack_inode_copy_up_xattr(const char *name)
+static int smack_inode_copy_up_xattr(struct dentry *src, const char *name)
 {
 	/*
 	 * Return 1 if this is the smack access Smack attribute.
-- 
2.43.0

