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SubjectRe: [PATCH v2 2/2] kobject: Fix -Wstringop-truncation warning
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Le 25/06/2018 à 14:45, Stafford Horne a écrit :
> When compiling with GCC 9.0.0 I am seeing the following warning:
>
> In function ‘fill_kobj_path’,
> inlined from ‘kobject_get_path’ at lib/kobject.c:155:2:
> lib/kobject.c:128:3: warning: ‘strncpy’ output truncated before terminating nul copying as many bytes from a string as its length [-Wstringop-truncation]
> strncpy(path + length, kobject_name(parent), cur);
> ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> lib/kobject.c: In function ‘kobject_get_path’:
> lib/kobject.c:125:13: note: length computed here
> int cur = strlen(kobject_name(parent));
> ^~~~~~~~~~~~~~~~~~~~~~~~~~~~
>
> This is not really an issue since the buffer we are writing to is
> pre-zero'd and we have already allocated the buffer based on the
> calculated strlen size and accounted for the terminating '\0'.
> Just use memcpy() instead.

If we are already sure the destination is big enough, why not just do a
strcpy() and drop the 'cur = strlen()' ?

Christophe

>
> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
> Cc: Arnd Bergmann <arnd@arndb.de>
> Cc: Eric Biggers <ebiggers3@gmail.com>
> Signed-off-by: Stafford Horne <shorne@gmail.com>
> ---
> lib/kobject.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/lib/kobject.c b/lib/kobject.c
> index 18989b5b3b56..e876957743c8 100644
> --- a/lib/kobject.c
> +++ b/lib/kobject.c
> @@ -125,7 +125,7 @@ static void fill_kobj_path(struct kobject *kobj, char *path, int length)
> int cur = strlen(kobject_name(parent));
> /* back up enough to print this name with '/' */
> length -= cur;
> - strncpy(path + length, kobject_name(parent), cur);
> + memcpy(path + length, kobject_name(parent), cur);
> *(path + --length) = '/';
> }
>
>

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