On Mon, Oct 26, 2020 at 05:10:19PM +0100, Arnd Bergmann wrote:
> From: Arnd Bergmann <arnd@xxxxxxxx>
>
> The way that bpmp_populate_debugfs_inband() uses strncpy()
> and strncat() makes no sense since the size argument for
> the first is insufficient to contain the trailing '/'
> and the second passes the length of the input rather than
> the output, which triggers a warning:
>
> In function 'strncat',
> inlined from 'bpmp_populate_debugfs_inband' at ../drivers/firmware/tegra/bpmp-debugfs.c:422:4:
> include/linux/string.h:289:30: warning: '__builtin_strncat' specified bound depends on the length of the source argument [-Wstringop-overflow=]
> 289 | #define __underlying_strncat __builtin_strncat
> | ^
> include/linux/string.h:367:10: note: in expansion of macro '__underlying_strncat'
> 367 | return __underlying_strncat(p, q, count);
> | ^~~~~~~~~~~~~~~~~~~~
> drivers/firmware/tegra/bpmp-debugfs.c: In function 'bpmp_populate_debugfs_inband':
> include/linux/string.h:288:29: note: length computed here
> 288 | #define __underlying_strlen __builtin_strlen
> | ^
> include/linux/string.h:321:10: note: in expansion of macro '__underlying_strlen'
> 321 | return __underlying_strlen(p);
>
> Simplify this to use an snprintf() instead.
>
> Fixes: 5e37b9c137ee ("firmware: tegra: Add support for in-band debug")
> Signed-off-by: Arnd Bergmann <arnd@xxxxxxxx>
> ---
> drivers/firmware/tegra/bpmp-debugfs.c | 6 +-----
> 1 file changed, 1 insertion(+), 5 deletions(-)
>
> diff --git a/drivers/firmware/tegra/bpmp-debugfs.c b/drivers/firmware/tegra/bpmp-debugfs.c
> index c1bbba9ee93a..9ec20ddc9a6b 100644
> --- a/drivers/firmware/tegra/bpmp-debugfs.c
> +++ b/drivers/firmware/tegra/bpmp-debugfs.c
> @@ -412,16 +412,12 @@ static int bpmp_populate_debugfs_inband(struct tegra_bpmp *bpmp,
> goto out;
> }
>
> - len = strlen(ppath) + strlen(name) + 1;
> + len = snprintf("%s%s/", pathlen, ppath, name);
Didn't you get any warnings with this? It should be
len = snprintf(pathbuf, pathlen, "%s%s/", ppath, name);
right?
> if (len >= pathlen) {
> err = -EINVAL;
> goto out;
> }
>
> - strncpy(pathbuf, ppath, pathlen);
> - strncat(pathbuf, name, strlen(name));
> - strcat(pathbuf, "/");
> -
> err = bpmp_populate_debugfs_inband(bpmp, dentry,
> pathbuf);
> if (err < 0)
> --
> 2.27.0
>
