linux-kernel - [PATCH] objtool: check: give big enough buffer for pv

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Message-Id: <20220114075756.838243-1-slyich@gmail.com>
Date:   Fri, 14 Jan 2022 07:57:56 +0000
From:   Sergei Trofimovich <slyich@...il.com>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     linux-kernel@...r.kernel.org,
        Sergei Trofimovich <slyich@...il.com>,
        Josh Poimboeuf <jpoimboe@...hat.com>
Subject: [PATCH] objtool: check: give big enough buffer for pv_ops

On gcc-12 build fails flagging possible buffer overflow:

    check.c: In function 'validate_call':
    check.c:2865:58: error: '%d' directive output may be truncated writing between 1 and 10 bytes into a region of size 9 [-Werror=format-truncation=]
     2865 |                 snprintf(pvname, sizeof(pvname), "pv_ops[%d]", idx);
          |                                                          ^~

I think it's a valid warning:

    static char pvname[16];
    int idx;
    ...
    idx = (rel->addend / sizeof(void *));
    snprintf(pvname, sizeof(pvname), "pv_ops[%d]", idx);

we have only 7 chars for %d while it could take up to 9.

CC: Josh Poimboeuf <jpoimboe@...hat.com>
CC: Peter Zijlstra <peterz@...radead.org>
---
 tools/objtool/check.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tools/objtool/check.c b/tools/objtool/check.c
index 8c1931eab5f1..0fae132ea59f 100644
--- a/tools/objtool/check.c
+++ b/tools/objtool/check.c
@@ -2852,7 +2852,7 @@ static inline bool func_uaccess_safe(struct symbol *func)
 
 static inline const char *call_dest_name(struct instruction *insn)
 {
-	static char pvname[16];
+	static char pvname[32];
 	struct reloc *rel;
 	int idx;
 
-- 
2.34.1