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From: Arnd Bergmann <arnd@kernel.org>
To: linux-kbuild@vger.kernel.org
Cc: Arnd Bergmann <arnd@arndb.de>,
	"Richard Russon" <ldm@flatcap.org>,
	Jens Axboe <axboe@kernel.dk>,
	Robert Moore <robert.moore@intel.com>,
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	Steven Rostedt <rostedt@goodmis.org>,
	Masami Hiramatsu <mhiramat@kernel.org>,
	Mathieu Desnoyers <mathieu.desnoyers@efficios.com>,
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	Nathan Chancellor <nathan@kernel.org>,
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	linux-trace-kernel@vger.kernel.org,
	Justin Stitt <justinstitt@google.com>
Subject: [PATCH 3/5] [v2] block/partitions/ldm: convert strncpy() to strscpy()
Date: Tue,  9 Apr 2024 16:00:56 +0200
Message-Id: <20240409140059.3806717-4-arnd@kernel.org>
In-Reply-To: <20240409140059.3806717-1-arnd@kernel.org>
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From: Arnd Bergmann <arnd@arndb.de>

The strncpy() here can cause a non-terminated string, which older gcc
versions such as gcc-9 warn about:

In function 'ldm_parse_tocblock',
    inlined from 'ldm_validate_tocblocks' at block/partitions/ldm.c:386:7,
    inlined from 'ldm_partition' at block/partitions/ldm.c:1457:7:
block/partitions/ldm.c:134:2: error: 'strncpy' specified bound 16 equals destination size [-Werror=stringop-truncation]
  134 |  strncpy (toc->bitmap1_name, data + 0x24, sizeof (toc->bitmap1_name));
      |  ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
block/partitions/ldm.c:145:2: error: 'strncpy' specified bound 16 equals destination size [-Werror=stringop-truncation]
  145 |  strncpy (toc->bitmap2_name, data + 0x46, sizeof (toc->bitmap2_name));
      |  ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

New versions notice that the code is correct after all because of the
following termination, but replacing the strncpy() with strscpy_pad()
or strcpy() avoids the warning and simplifies the code at the same time.

Use the padding version here to keep the existing behavior, in case
the code relies on not including uninitialized data.

Reviewed-by: Justin Stitt <justinstitt@google.com>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
---
 block/partitions/ldm.c | 6 ++----
 1 file changed, 2 insertions(+), 4 deletions(-)

diff --git a/block/partitions/ldm.c b/block/partitions/ldm.c
index 38e58960ae03..2bd42fedb907 100644
--- a/block/partitions/ldm.c
+++ b/block/partitions/ldm.c
@@ -131,8 +131,7 @@ static bool ldm_parse_tocblock (const u8 *data, struct tocblock *toc)
 		ldm_crit ("Cannot find TOCBLOCK, database may be corrupt.");
 		return false;
 	}
-	strncpy (toc->bitmap1_name, data + 0x24, sizeof (toc->bitmap1_name));
-	toc->bitmap1_name[sizeof (toc->bitmap1_name) - 1] = 0;
+	strscpy_pad(toc->bitmap1_name, data + 0x24, sizeof(toc->bitmap1_name));
 	toc->bitmap1_start = get_unaligned_be64(data + 0x2E);
 	toc->bitmap1_size  = get_unaligned_be64(data + 0x36);
 
@@ -142,8 +141,7 @@ static bool ldm_parse_tocblock (const u8 *data, struct tocblock *toc)
 				TOC_BITMAP1, toc->bitmap1_name);
 		return false;
 	}
-	strncpy (toc->bitmap2_name, data + 0x46, sizeof (toc->bitmap2_name));
-	toc->bitmap2_name[sizeof (toc->bitmap2_name) - 1] = 0;
+	strscpy_pad(toc->bitmap2_name, data + 0x46, sizeof(toc->bitmap2_name));
 	toc->bitmap2_start = get_unaligned_be64(data + 0x50);
 	toc->bitmap2_size  = get_unaligned_be64(data + 0x58);
 	if (strncmp (toc->bitmap2_name, TOC_BITMAP2,
-- 
2.39.2