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authorJustin Stitt <justinstitt@google.com>2023-07-27 23:53:24 +0200
committerTakashi Iwai <tiwai@suse.de>2023-07-29 13:53:39 +0200
commit44900c3ee4a1047bf896ca4cd9a9c69000f04701 (patch)
tree8654d6848e017c95f1e88a121f667c15d11365bf
parentALSA: hda/cs35l56: Do some clean up on probe error (diff)
downloadlinux-44900c3ee4a1047bf896ca4cd9a9c69000f04701.tar.xz
linux-44900c3ee4a1047bf896ca4cd9a9c69000f04701.zip
ALSA: xen-front: refactor deprecated strncpy
`strncpy` is deprecated for use on NUL-terminated destination strings [1]. A suitable replacement is `strscpy` [2] due to the fact that it guarantees NUL-termination on its destination buffer argument which is _not_ always the case for `strncpy`! It should be noted that, in this case, the destination buffer has a length strictly greater than the source string. Moreover, the source string is NUL-terminated (and so is the destination) which means there was no real bug happening here. Nonetheless, this patch would get us one step closer to eliminating the `strncpy` API in the kernel, as its use is too ambiguous. We need to favor less ambiguous replacements such as: strscpy, strscpy_pad, strtomem and strtomem_pad (amongst others). Technically, my patch yields subtly different behavior. The original implementation with `strncpy` would fill the entire destination buffer with null bytes [3] while `strscpy` will leave the junk, uninitialized bytes trailing after the _mandatory_ NUL-termination. So, if somehow `pcm->name` or `card->driver/shortname/longname` require this NUL-padding behavior then `strscpy_pad` should be used. My interpretation, though, is that the aforementioned fields are just fine as NUL-terminated strings. Please correct my assumptions if needed and I'll send in a v2. [1]: www.kernel.org/doc/html/latest/process/deprecated.html#strncpy-on-nul-terminated-strings [2]: manpages.debian.org/testing/linux-manual-4.8/strscpy.9.en.html [3]: https://linux.die.net/man/3/strncpy Link: https://github.com/KSPP/linux/issues/90 Signed-off-by: Justin Stitt <justinstitt@google.com> Reviewed-by: Kees Cook <keescook@chromium.org> Link: https://lore.kernel.org/r/20230727-sound-xen-v1-1-89dd161351f1@google.com Signed-off-by: Takashi Iwai <tiwai@suse.de>
-rw-r--r--sound/xen/xen_snd_front_alsa.c8
1 files changed, 4 insertions, 4 deletions
diff --git a/sound/xen/xen_snd_front_alsa.c b/sound/xen/xen_snd_front_alsa.c
index db917453a473..7a3dfce97c15 100644
--- a/sound/xen/xen_snd_front_alsa.c
+++ b/sound/xen/xen_snd_front_alsa.c
@@ -783,7 +783,7 @@ static int new_pcm_instance(struct xen_snd_front_card_info *card_info,
pcm->info_flags = 0;
/* we want to handle all PCM operations in non-atomic context */
pcm->nonatomic = true;
- strncpy(pcm->name, "Virtual card PCM", sizeof(pcm->name));
+ strscpy(pcm->name, "Virtual card PCM", sizeof(pcm->name));
if (instance_cfg->num_streams_pb)
snd_pcm_set_ops(pcm, SNDRV_PCM_STREAM_PLAYBACK,
@@ -835,9 +835,9 @@ int xen_snd_front_alsa_init(struct xen_snd_front_info *front_info)
goto fail;
}
- strncpy(card->driver, XENSND_DRIVER_NAME, sizeof(card->driver));
- strncpy(card->shortname, cfg->name_short, sizeof(card->shortname));
- strncpy(card->longname, cfg->name_long, sizeof(card->longname));
+ strscpy(card->driver, XENSND_DRIVER_NAME, sizeof(card->driver));
+ strscpy(card->shortname, cfg->name_short, sizeof(card->shortname));
+ strscpy(card->longname, cfg->name_long, sizeof(card->longname));
ret = snd_card_register(card);
if (ret < 0)