linux-kernel - [PATCH] x86/callthunks: Fix some potential string truncation in callthunks_debugfs

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Date: Sun, 17 Dec 2023 10:01:41 +0100
From: Christophe JAILLET <christophe.jaillet@...adoo.fr>
To: Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	Borislav Petkov <bp@...en8.de>,
	Dave Hansen <dave.hansen@...ux.intel.com>,
	x86@...nel.org,
	"H. Peter Anvin" <hpa@...or.com>
Cc: linux-kernel@...r.kernel.org,
	kernel-janitors@...r.kernel.org,
	Christophe JAILLET <christophe.jaillet@...adoo.fr>
Subject: [PATCH] x86/callthunks: Fix some potential string truncation in callthunks_debugfs_init()

When compiled with W=1, we get:
  arch/x86/kernel/callthunks.c: In function ‘callthunks_debugfs_init’:
  arch/x86/kernel/callthunks.c:394:35: error: ‘%lu’ directive writing between 1 and 10 bytes into a region of size 7 [-Werror=format-overflow=]
    394 |                 sprintf(name, "cpu%lu", cpu);
        |                                   ^~~
  arch/x86/kernel/callthunks.c:394:31: note: directive argument in the range [0, 4294967294]
    394 |                 sprintf(name, "cpu%lu", cpu);
        |                               ^~~~~~~~
  arch/x86/kernel/callthunks.c:394:17: note: ‘sprintf’ output between 5 and 14 bytes into a destination of size 10
    394 |                 sprintf(name, "cpu%lu", cpu);
        |

So, give some more space to 'name' to silence the warning. (and fix the
issue should a lucky one have a config with so many CPU!)

Signed-off-by: Christophe JAILLET <christophe.jaillet@...adoo.fr>
---
 arch/x86/kernel/callthunks.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/x86/kernel/callthunks.c b/arch/x86/kernel/callthunks.c
index cf7e5be1b844..26182a7d12b3 100644
--- a/arch/x86/kernel/callthunks.c
+++ b/arch/x86/kernel/callthunks.c
@@ -388,7 +388,7 @@ static int __init callthunks_debugfs_init(void)
 	dir = debugfs_create_dir("callthunks", NULL);
 	for_each_possible_cpu(cpu) {
 		void *arg = (void *)cpu;
-		char name [10];
+		char name[14];
 
 		sprintf(name, "cpu%lu", cpu);
 		debugfs_create_file(name, 0644, dir, arg, &dfs_ops);
-- 
2.34.1