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Date: Fri, 30 Mar 2018 10:53:08 +0200
From: Salvatore Mesoraca <s.mesoraca16@...il.com>
To: linux-kernel@...r.kernel.org
Cc: kernel-hardening@...ts.openwall.com,
Ingo Molnar <mingo@...hat.com>,
Kees Cook <keescook@...omium.org>,
Salvatore Mesoraca <s.mesoraca16@...il.com>,
Steven Rostedt <rostedt@...dmis.org>
Subject: [v2] ftrace: drop a VLA in module_exists()
Avoid a VLA[1] by using a real constant expression instead of a variable.
The compiler should be able to optimize the original code and avoid using
an actual VLA. Anyway this change is useful because it will avoid a false
positive with -Wvla, it might also help the compiler generating better
code.
[1] https://lkml.org/lkml/2018/3/7/621
Signed-off-by: Salvatore Mesoraca <s.mesoraca16@...il.com>
---
kernel/trace/ftrace.c | 7 +++----
1 file changed, 3 insertions(+), 4 deletions(-)
diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
index eac9ce2..16bbf06 100644
--- a/kernel/trace/ftrace.c
+++ b/kernel/trace/ftrace.c
@@ -3902,14 +3902,13 @@ static bool module_exists(const char *module)
{
/* All modules have the symbol __this_module */
const char this_mod[] = "__this_module";
- const int modname_size = MAX_PARAM_PREFIX_LEN + sizeof(this_mod) + 1;
- char modname[modname_size + 1];
+ char modname[MAX_PARAM_PREFIX_LEN + sizeof(this_mod) + 2];
unsigned long val;
int n;
- n = snprintf(modname, modname_size + 1, "%s:%s", module, this_mod);
+ n = snprintf(modname, sizeof(modname), "%s:%s", module, this_mod);
- if (n > modname_size)
+ if (n > sizeof(modname) - 1)
return false;
val = module_kallsyms_lookup_name(modname);
--
1.9.1
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