diff mbox series

[07/11] block/partitions/ldm: convert strncpy() to strscpy()

Message ID 20240328140512.4148825-8-arnd@kernel.org (mailing list archive)
State New, archived
Headers show
Series address remaining stringop-truncation warnings | expand

Commit Message

Arnd Bergmann March 28, 2024, 2:04 p.m. UTC 
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.

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

Comments

Justin Stitt March 28, 2024, 11:24 p.m. UTC | #1 
Hi,

On Thu, Mar 28, 2024 at 03:04:51PM +0100, Arnd Bergmann wrote:
> 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.
> 
> Signed-off-by: Arnd Bergmann <arnd@arndb.de>

Thanks for the patch!

This helps towards: https://github.com/KSPP/linux/issues/90

Reviewed-by: Justin Stitt <justinstitt@google.com>

> ---
>  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
> 

Thanks
Justin
diff mbox series

Patch

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,