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From:   Richard Guy Briggs <rgb@redhat.com>
To:     Linux-Audit Mailing List <linux-audit@redhat.com>,
        LKML <linux-kernel@vger.kernel.org>
Cc:     Eric Paris <eparis@redhat.com>, Paul Moore <paul@paul-moore.com>,
        Steve Grubb <sgrubb@redhat.com>,
        Kees Cook <keescook@chromium.org>,
        Richard Guy Briggs <rgb@redhat.com>
Subject: [PATCH ghak21 V2 2/4] audit: link denied should not directly generate PATH record
Date:   Mon, 12 Mar 2018 02:31:18 -0400
Message-Id: <9ed76ccb239078ad5a2808d23c7b7f1738b0b2b8.1520835596.git.rgb@redhat.com>
In-Reply-To: <cover.1520835596.git.rgb@redhat.com>
References: <cover.1520835596.git.rgb@redhat.com>
In-Reply-To: <cover.1520835596.git.rgb@redhat.com>
References: <cover.1520835596.git.rgb@redhat.com>
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

Audit link denied events generate duplicate PATH records which disagree
in different ways from symlink and hardlink denials.
audit_log_link_denied() should not directly generate PATH records.
While we're at it, remove the now useless struct path argument.

See: https://github.com/linux-audit/audit-kernel/issues/21
Signed-off-by: Richard Guy Briggs <rgb@redhat.com>
---
 fs/namei.c            |  2 +-
 include/linux/audit.h |  6 ++----
 kernel/audit.c        | 17 ++---------------
 3 files changed, 5 insertions(+), 20 deletions(-)

diff --git a/fs/namei.c b/fs/namei.c
index 9cc91fb..50d2533 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -1011,7 +1011,7 @@ static int may_linkat(struct path *link)
 	if (safe_hardlink_source(inode) || inode_owner_or_capable(inode))
 		return 0;
 
-	audit_log_link_denied("linkat", link);
+	audit_log_link_denied("linkat");
 	return -EPERM;
 }
 
diff --git a/include/linux/audit.h b/include/linux/audit.h
index af410d9..75d5b03 100644
--- a/include/linux/audit.h
+++ b/include/linux/audit.h
@@ -146,8 +146,7 @@ extern void		    audit_log_d_path(struct audit_buffer *ab,
 					     const struct path *path);
 extern void		    audit_log_key(struct audit_buffer *ab,
 					  char *key);
-extern void		    audit_log_link_denied(const char *operation,
-						  const struct path *link);
+extern void		    audit_log_link_denied(const char *operation);
 extern void		    audit_log_lost(const char *message);
 
 extern int audit_log_task_context(struct audit_buffer *ab);
@@ -194,8 +193,7 @@ static inline void audit_log_d_path(struct audit_buffer *ab,
 { }
 static inline void audit_log_key(struct audit_buffer *ab, char *key)
 { }
-static inline void audit_log_link_denied(const char *string,
-					 const struct path *link)
+static inline void audit_log_link_denied(const char *string)
 { }
 static inline int audit_log_task_context(struct audit_buffer *ab)
 {
diff --git a/kernel/audit.c b/kernel/audit.c
index 7026d69..e54deaf 100644
--- a/kernel/audit.c
+++ b/kernel/audit.c
@@ -2301,36 +2301,23 @@ void audit_log_task_info(struct audit_buffer *ab, struct task_struct *tsk)
 /**
  * audit_log_link_denied - report a link restriction denial
  * @operation: specific link operation
- * @link: the path that triggered the restriction
  */
-void audit_log_link_denied(const char *operation, const struct path *link)
+void audit_log_link_denied(const char *operation)
 {
 	struct audit_buffer *ab;
-	struct audit_names *name;
 
 	if (!audit_enabled || audit_dummy_context())
 		return;
 
-	name = kzalloc(sizeof(*name), GFP_NOFS);
-	if (!name)
-		return;
-
 	/* Generate AUDIT_ANOM_LINK with subject, operation, outcome. */
 	ab = audit_log_start(current->audit_context, GFP_KERNEL,
 			     AUDIT_ANOM_LINK);
 	if (!ab)
-		goto out;
+		return;
 	audit_log_format(ab, "op=%s", operation);
 	audit_log_task_info(ab, current);
 	audit_log_format(ab, " res=0");
 	audit_log_end(ab);
-
-	/* Generate AUDIT_PATH record with object. */
-	name->type = AUDIT_TYPE_NORMAL;
-	audit_copy_inode(name, link->dentry, d_backing_inode(link->dentry));
-	audit_log_name(current->audit_context, name, link, 0, NULL);
-out:
-	kfree(name);
 }
 
 /**
-- 
1.8.3.1