[PATCH v7 15/49] audit: allow audit code to satisfy getname requests from its names_list

[Jeff Layton <jlayton@redhat.com>]

Currently, if we call getname() on a userland string more than once,
we'll get multiple copies of the string and multiple audit_names
records.

Add a function that will allow the audit_names code to satisfy getname
requests using info from the audit_names list, avoiding a new allocation
and audit_names records.

Signed-off-by: Jeff Layton <jlayton@redhat.com>
---
 fs/namei.c            |  4 ++++
 include/linux/audit.h |  8 ++++++++
 kernel/auditsc.c      | 23 +++++++++++++++++++++++
 3 files changed, 35 insertions(+)

diff --git a/fs/namei.c b/fs/namei.c
index 60db390..01a2dd18 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -130,6 +130,10 @@ getname_flags(const char __user *filename, int flags, int *empty)
 	char *kname;
 	int len;
 
+	result = audit_reusename(filename);
+	if (result)
+		return result;
+
 	/* FIXME: create dedicated slabcache? */
 	result = kzalloc(sizeof(*result), GFP_KERNEL);
 	if (unlikely(!result))
diff --git a/include/linux/audit.h b/include/linux/audit.h
index d361921..ea58de3 100644
--- a/include/linux/audit.h
+++ b/include/linux/audit.h
@@ -469,6 +469,7 @@ extern void __audit_syscall_entry(int arch,
 				  int major, unsigned long a0, unsigned long a1,
 				  unsigned long a2, unsigned long a3);
 extern void __audit_syscall_exit(int ret_success, long ret_value);
+extern struct getname_info *__audit_reusename(const __user char *uptr);
 extern void __audit_getname(struct getname_info *ginfo);
 extern void audit_putname(struct getname_info *ginfo);
 extern void __audit_inode(const char *name, const struct dentry *dentry,
@@ -505,6 +506,12 @@ static inline void audit_syscall_exit(void *pt_regs)
 		__audit_syscall_exit(success, return_code);
 	}
 }
+static inline struct getname_info *audit_reusename(const __user char *name)
+{
+	if (unlikely(!audit_dummy_context()))
+		return __audit_reusename(name);
+	return NULL;
+}
 static inline void audit_getname(struct getname_info *name)
 {
 	if (unlikely(!audit_dummy_context()))
@@ -642,6 +649,7 @@ extern int audit_signals;
 #define audit_syscall_entry(ta,a,b,c,d,e) do { ; } while (0)
 #define audit_syscall_exit(r) do { ; } while (0)
 #define audit_dummy_context() 1
+#define audit_reusename(g) ({ NULL; })
 #define audit_getname(n) do { ; } while (0)
 #define audit_putname(n) do { ; } while (0)
 #define __audit_inode(n,d,p) do { ; } while (0)
diff --git a/kernel/auditsc.c b/kernel/auditsc.c
index 0ba346b..89974ca 100644
--- a/kernel/auditsc.c
+++ b/kernel/auditsc.c
@@ -2035,6 +2035,29 @@ static struct audit_names *audit_alloc_name(struct audit_context *context,
 }
 
 /**
+ * audit_reusename - fill out getname_info with info from existing entry
+ * @uptr: userland ptr to pathname
+ *
+ * Search the audit_names list for the current audit context. If there is an
+ * existing entry with a matching "uptr" then return the getname_info
+ * associated with that audit_name. If not, return NULL.
+ */
+struct getname_info *
+__audit_reusename(const __user char *uptr)
+{
+	struct audit_context *context = current->audit_context;
+	struct audit_names *n;
+
+	list_for_each_entry(n, &context->names_list, list) {
+		if (!n->ginfo)
+			continue;
+		if (n->ginfo->uptr == uptr)
+			return n->ginfo;
+	}
+	return NULL;
+}
+
+/**
  * audit_getname - add a name to the list
  * @name: name to add
  *
-- 
1.7.11.4