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From:   Sergei Trofimovich <slyich@gmail.com>
To:     Josh Poimboeuf <jpoimboe@redhat.com>
Cc:     linux-kernel@vger.kernel.org,
        Sergei Trofimovich <slyich@gmail.com>,
        Peter Zijlstra <peterz@infradead.org>
Subject: [PATCH v2] objtool: check: give big enough buffer for pv_ops
Date:   Thu, 20 Jan 2022 23:37:48 +0000
Message-Id: <20220120233748.2062559-1-slyich@gmail.com>
In-Reply-To: <20220120230932.vgd3sj4yuk7mhmno@treble>
References: <20220120230932.vgd3sj4yuk7mhmno@treble>
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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@redhat.com>
CC: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Sergei Trofimovich <slyich@gmail.com>
---
Change since v1: added missing S-O-B.
 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 c2d2ab9a2861..f5bed94e4558 100644
--- a/tools/objtool/check.c
+++ b/tools/objtool/check.c
@@ -2854,7 +2854,7 @@ 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