linux-kernel - [PATCH 5.16 107/126] objtool: Fix truncated string warning

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Date:   Mon,  7 Feb 2022 12:07:18 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Adam Borowski <kilobyte@...band.pl>,
        Martin Liška <mliska@...e.cz>,
        Sergei Trofimovich <slyich@...il.com>,
        Josh Poimboeuf <jpoimboe@...hat.com>,
        Sasha Levin <sashal@...nel.org>
Subject: [PATCH 5.16 107/126] objtool: Fix truncated string warning

From: Sergei Trofimovich <slyich@...il.com>

[ Upstream commit 82880283d7fcd0a1d20964a56d6d1a5cc0df0713 ]

On GCC 12, the build fails due to a possible truncated string:

    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);
          |                                                          ^~

In theory it's a valid bug:

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

There are only 7 chars for %d while it could take up to 9, so the
printed "pv_ops[%d]" string could get truncated.

In reality the bug should never happen, because pv_ops only has ~80
entries, so 7 chars for the integer is more than enough.  Still, it's
worth fixing.  Bump the buffer size by 2 bytes to silence the warning.

[ jpoimboe: changed size to 19; massaged changelog ]

Fixes: db2b0c5d7b6f ("objtool: Support pv_opsindirect calls for noinstr")
Reported-by: Adam Borowski <kilobyte@...band.pl>
Reported-by: Martin Liška <mliska@...e.cz>
Signed-off-by: Sergei Trofimovich <slyich@...il.com>
Signed-off-by: Josh Poimboeuf <jpoimboe@...hat.com>
Link: https://lore.kernel.org/r/20220120233748.2062559-1-slyich@gmail.com
Signed-off-by: Sasha Levin <sashal@...nel.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 21735829b860c..750ef1c446c8a 100644
--- a/tools/objtool/check.c
+++ b/tools/objtool/check.c
@@ -2823,7 +2823,7 @@ 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[19];
 	struct reloc *rel;
 	int idx;
 
-- 
2.34.1