linux-kernel - [tip: objtool/urgent] objtool: Fix truncated string warning

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Message-ID: <164363069582.16921.3459888464931150219.tip-bot2@tip-bot2>
Date:   Mon, 31 Jan 2022 12:04:55 -0000
From:   "tip-bot2 for Sergei Trofimovich" <tip-bot2@...utronix.de>
To:     linux-tip-commits@...r.kernel.org
Cc:     Adam Borowski <kilobyte@...band.pl>, mliska@...e.cz,
        Sergei Trofimovich <slyich@...il.com>,
        Josh Poimboeuf <jpoimboe@...hat.com>, x86@...nel.org,
        linux-kernel@...r.kernel.org
Subject: [tip: objtool/urgent] objtool: Fix truncated string warning

The following commit has been merged into the objtool/urgent branch of tip:

Commit-ID:     82880283d7fcd0a1d20964a56d6d1a5cc0df0713
Gitweb:        https://git.kernel.org/tip/82880283d7fcd0a1d20964a56d6d1a5cc0df0713
Author:        Sergei Trofimovich <slyich@...il.com>
AuthorDate:    Thu, 20 Jan 2022 23:37:48 
Committer:     Josh Poimboeuf <jpoimboe@...hat.com>
CommitterDate: Mon, 24 Jan 2022 10:09:06 -08:00

objtool: Fix truncated string warning

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
---
 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 c2d2ab9..7c33ec6 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[19];
 	struct reloc *rel;
 	int idx;