ima: Move ima_reset_appraise_flags() call to post hooks

hulk inclusion
category: feature
feature: IMA Digest Lists extension
bugzilla: 46797

---------------------------

ima_inode_setxattr() and ima_inode_removexattr() hooks are called before an
operation is performed. Thus, ima_reset_appraise_flags() should not be
called there, as flags might be unnecessarily reset if the operation is
denied.

This patch introduces the post hooks ima_inode_post_setxattr() and
ima_inode_post_removexattr(), and adds the call to
ima_reset_appraise_flags() in the new functions.
Signed-off-by: NRoberto Sassu <roberto.sassu@huawei.com>
Reviewed-by: NJason Yan <yanaijie@huawei.com>
Signed-off-by: NZheng Zengkai <zhengzengkai@huawei.com>

fs/xattr.c

@@ -16,6 +16,7 @@
 #include <linux/namei.h>
 #include <linux/security.h>
 #include <linux/evm.h>
+#include <linux/ima.h>
 #include <linux/syscalls.h>
 #include <linux/export.h>
 #include <linux/fsnotify.h>
@@ -474,6 +475,7 @@ __vfs_removexattr_locked(struct dentry *dentry, const char *name,
 
 	if (!error) {
 		fsnotify_xattr(dentry);
+		ima_inode_post_removexattr(dentry, name);
 		evm_inode_post_removexattr(dentry, name);
 	}
 

include/linux/ima.h

@@ -144,7 +144,13 @@ extern bool is_ima_appraise_enabled(void);
 extern void ima_inode_post_setattr(struct dentry *dentry);
 extern int ima_inode_setxattr(struct dentry *dentry, const char *xattr_name,
 		       const void *xattr_value, size_t xattr_value_len);
+extern void ima_inode_post_setxattr(struct dentry *dentry,
+				    const char *xattr_name,
+				    const void *xattr_value,
+				    size_t xattr_value_len);
 extern int ima_inode_removexattr(struct dentry *dentry, const char *xattr_name);
+extern void ima_inode_post_removexattr(struct dentry *dentry,
+				       const char *xattr_name);
 #else
 static inline bool is_ima_appraise_enabled(void)
 {
@@ -164,11 +170,23 @@ static inline int ima_inode_setxattr(struct dentry *dentry,
 	return 0;
 }
 
+static inline void ima_inode_post_setxattr(struct dentry *dentry,
+					   const char *xattr_name,
+					   const void *xattr_value,
+					   size_t xattr_value_len)
+{
+}
+
 static inline int ima_inode_removexattr(struct dentry *dentry,
 					const char *xattr_name)
 {
 	return 0;
 }
+
+static inline void ima_inode_post_removexattr(struct dentry *dentry,
+					      const char *xattr_name)
+{
+}
 #endif /* CONFIG_IMA_APPRAISE */
 
 #if defined(CONFIG_IMA_APPRAISE) && defined(CONFIG_INTEGRITY_TRUSTED_KEYRING)

security/integrity/ima/ima_appraise.c

@@ -569,21 +569,40 @@ int ima_inode_setxattr(struct dentry *dentry, const char *xattr_name,
 	if (result == 1) {
 		if (!xattr_value_len || (xvalue->type >= IMA_XATTR_LAST))
 			return -EINVAL;
-		ima_reset_appraise_flags(d_backing_inode(dentry),
-			xvalue->type == EVM_IMA_XATTR_DIGSIG);
 		result = 0;
 	}
 	return result;
 }
 
+void ima_inode_post_setxattr(struct dentry *dentry, const char *xattr_name,
+			     const void *xattr_value, size_t xattr_value_len)
+{
+	const struct evm_ima_xattr_data *xvalue = xattr_value;
+	int result;
+
+	result = ima_protect_xattr(dentry, xattr_name, xattr_value,
+				   xattr_value_len);
+	if (result == 1)
+		ima_reset_appraise_flags(d_backing_inode(dentry),
+			xvalue->type == EVM_IMA_XATTR_DIGSIG);
+}
+
 int ima_inode_removexattr(struct dentry *dentry, const char *xattr_name)
 {
 	int result;
 
 	result = ima_protect_xattr(dentry, xattr_name, NULL, 0);
 	if (result == 1) {
-		ima_reset_appraise_flags(d_backing_inode(dentry), 0);
 		result = 0;
 	}
 	return result;
 }
+
+void ima_inode_post_removexattr(struct dentry *dentry, const char *xattr_name)
+{
+	int result;
+
+	result = ima_protect_xattr(dentry, xattr_name, NULL, 0);
+	if (result == 1)
+		ima_reset_appraise_flags(d_backing_inode(dentry), 0);
+}

security/security.c

@@ -1309,6 +1309,7 @@ void security_inode_post_setxattr(struct dentry *dentry, const char *name,
 	if (unlikely(IS_PRIVATE(d_backing_inode(dentry))))
 		return;
 	call_void_hook(inode_post_setxattr, dentry, name, value, size, flags);
+	ima_inode_post_setxattr(dentry, name, value, size);
 	evm_inode_post_setxattr(dentry, name, value, size);
 }