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| author | Justin Stitt <justinstitt@google.com> | 2023-07-27 22:09:29 +0000 |
|---|---|---|
| committer | Takashi Iwai <tiwai@suse.de> | 2023-07-29 13:53:56 +0200 |
| commit | 2ad27caab44583eb38b71d90a364e5670b4c7c5a (patch) | |
| tree | 2796a78935ad121a583f34f66c50f9f206a0f36b | |
| parent | 44900c3ee4a1047bf896ca4cd9a9c69000f04701 (diff) | |
| download | linux-stable-2ad27caab44583eb38b71d90a364e5670b4c7c5a.tar.gz linux-stable-2ad27caab44583eb38b71d90a364e5670b4c7c5a.tar.bz2 linux-stable-2ad27caab44583eb38b71d90a364e5670b4c7c5a.zip | |
ALSA: bcd2000: 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
`card->driver` or `card->shortname` 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
Link: https://lore.kernel.org/r/20230727-sound-xen-v1-1-89dd161351f1@google.com (related ALSA patch)
Signed-off-by: Justin Stitt <justinstitt@google.com>
Link: https://lore.kernel.org/r/20230727-sound-usb-bcd2000-v1-1-0dc73684b2f0@google.com
Signed-off-by: Takashi Iwai <tiwai@suse.de>
| -rw-r--r-- | sound/usb/bcd2000/bcd2000.c | 4 |
1 files changed, 2 insertions, 2 deletions
diff --git a/sound/usb/bcd2000/bcd2000.c b/sound/usb/bcd2000/bcd2000.c index 7aec0a95c609..392b4d8e9e76 100644 --- a/sound/usb/bcd2000/bcd2000.c +++ b/sound/usb/bcd2000/bcd2000.c @@ -395,8 +395,8 @@ static int bcd2000_probe(struct usb_interface *interface, snd_card_set_dev(card, &interface->dev); - strncpy(card->driver, "snd-bcd2000", sizeof(card->driver)); - strncpy(card->shortname, "BCD2000", sizeof(card->shortname)); + strscpy(card->driver, "snd-bcd2000", sizeof(card->driver)); + strscpy(card->shortname, "BCD2000", sizeof(card->shortname)); usb_make_path(bcd2k->dev, usb_path, sizeof(usb_path)); snprintf(bcd2k->card->longname, sizeof(bcd2k->card->longname), "Behringer BCD2000 at %s", |