linux-kernel - [PATCH] gcc-plugins/stackleak: Avoid assignment for unused macro argument

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [thread-next>] [day] [month] [year] [list]

Message-ID: <202004020103.731F201@keescook>
Date:   Thu, 2 Apr 2020 01:10:47 -0700
From:   Kees Cook <keescook@...omium.org>
To:     kernel-hardening@...ts.openwall.com
Cc:     Alexander Popov <alex.popov@...ux.com>,
        Emese Revfy <re.emese@...il.com>, linux-kernel@...r.kernel.org
Subject: [PATCH] gcc-plugins/stackleak: Avoid assignment for unused macro
 argument

With GCC version >= 8, the cgraph_create_edge() macro argument using
"frequency" goes unused. Instead of assigning a temporary variable for
the argument, pass the compute_call_stmt_bb_frequency() call directly
as the macro argument so that it will just not be uncalled when it is
not wanted by the macros.

Silences the warning:

scripts/gcc-plugins/stackleak_plugin.c:54:6: warning: variable ‘frequency’ set but not used [-Wunused-but-set-variable]

Now builds cleanly with gcc-7 and gcc-9. Both boot and pass
STACKLEAK_ERASING LKDTM test.

Signed-off-by: Kees Cook <keescook@...omium.org>
---
 scripts/gcc-plugins/stackleak_plugin.c | 5 ++---
 1 file changed, 2 insertions(+), 3 deletions(-)

diff --git a/scripts/gcc-plugins/stackleak_plugin.c b/scripts/gcc-plugins/stackleak_plugin.c
index dbd37460c573..cc75eeba0be1 100644
--- a/scripts/gcc-plugins/stackleak_plugin.c
+++ b/scripts/gcc-plugins/stackleak_plugin.c
@@ -51,7 +51,6 @@ static void stackleak_add_track_stack(gimple_stmt_iterator *gsi, bool after)
 	gimple stmt;
 	gcall *stackleak_track_stack;
 	cgraph_node_ptr node;
-	int frequency;
 	basic_block bb;
 
 	/* Insert call to void stackleak_track_stack(void) */
@@ -68,9 +67,9 @@ static void stackleak_add_track_stack(gimple_stmt_iterator *gsi, bool after)
 	bb = gimple_bb(stackleak_track_stack);
 	node = cgraph_get_create_node(track_function_decl);
 	gcc_assert(node);
-	frequency = compute_call_stmt_bb_frequency(current_function_decl, bb);
 	cgraph_create_edge(cgraph_get_node(current_function_decl), node,
-			stackleak_track_stack, bb->count, frequency);
+			stackleak_track_stack, bb->count,
+			compute_call_stmt_bb_frequency(current_function_decl, bb));
 }
 
 static bool is_alloca(gimple stmt)
-- 
2.20.1


-- 
Kees Cook