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Message-Id: <1491513513-84351-8-git-send-email-keescook@chromium.org>
Date: Thu, 6 Apr 2017 14:18:22 -0700
From: Kees Cook <keescook@...omium.org>
To: kernel-hardening@...ts.openwall.com
Cc: Kees Cook <keescook@...omium.org>,
Michael Leibowitz <michael.leibowitz@...el.com>
Subject: [PATCH 07/18] randstruct: Whitelist struct security_hook_heads cast
The LSM initialization routines walk security_hook_heads as an array
of struct list_head instead of via names to avoid a ton of needless
source. Whitelist this to avoid the false positive warning from the
plugin:
security/security.c: In function ‘security_init’:
security/security.c:59:20: note: found mismatched op0 struct pointer types: ‘struct list_head’ and ‘struct security_hook_heads’
struct list_head *list = (struct list_head *) &security_hook_heads;
^
Signed-off-by: Kees Cook <keescook@...omium.org>
---
scripts/gcc-plugins/randomize_layout_plugin.c | 38 ++++++++++++++++++++++++++-
1 file changed, 37 insertions(+), 1 deletion(-)
diff --git a/scripts/gcc-plugins/randomize_layout_plugin.c b/scripts/gcc-plugins/randomize_layout_plugin.c
index dc03a6beb06b..63c654a00249 100644
--- a/scripts/gcc-plugins/randomize_layout_plugin.c
+++ b/scripts/gcc-plugins/randomize_layout_plugin.c
@@ -762,6 +762,33 @@ static void handle_local_var_initializers(void)
}
}
+static bool type_name_eq(gimple stmt, const_tree type_tree, const char *wanted_name)
+{
+ const char *type_name;
+
+ if (type_tree == NULL_TREE)
+ return false;
+
+ switch (TREE_CODE(type_tree)) {
+ case RECORD_TYPE:
+ type_name = TYPE_NAME_POINTER(type_tree);
+ break;
+ default:
+ inform(gimple_location(stmt), "unhandled cast comparison: %qT\n", type_tree);
+ debug_tree(type_tree);
+ return false;
+ }
+
+ return strcmp(type_name, wanted_name) == 0;
+}
+
+static bool whitelisted_cast(gimple stmt,
+ const_tree lhs_tree, const_tree rhs_tree,
+ const char *lhs, const char *rhs)
+{
+ return type_name_eq(stmt, lhs_tree, lhs) && type_name_eq(stmt, rhs_tree, rhs);
+}
+
/*
* iterate over all statements to find "bad" casts:
* those where the address of the start of a structure is cast
@@ -859,8 +886,17 @@ static unsigned int find_bad_casts_execute(void)
#ifndef __DEBUG_PLUGIN
if (lookup_attribute("randomize_performed", TYPE_ATTRIBUTES(op0_type)))
+ {
#endif
- inform(gimple_location(stmt), "found mismatched op0 struct pointer types: %qT and %qT\n", ptr_lhs_type, op0_type);
+ /*
+ * Whitelist walking struct security_hook_heads
+ * as an array of struct list_head.
+ */
+ if (whitelisted_cast(stmt, ptr_lhs_type, op0_type, "list_head", "security_hook_heads"))
+ continue;
+
+ inform(gimple_location(stmt), "found mismatched op0 struct pointer types: %qT and %qT\n", ptr_lhs_type, op0_type);
+ }
} else {
const_tree ssa_name_var = SSA_NAME_VAR(rhs1);
/* skip bogus type casts introduced by container_of */
--
2.7.4
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