[PATCH linux-next] ALSA: control-led: use strscpy() to instead of strncpy()
From: Xu Panda xu.panda@zte.com.cn
The implementation of strscpy() is more robust and safer. That's now the recommended way to copy NUL-terminated strings.
Signed-off-by: Xu Panda xu.panda@zte.com.cn Signed-off-by: Yang Yang yang.yang29@zte.com.cn --- sound/core/control_led.c | 3 +-- 1 file changed, 1 insertion(+), 2 deletions(-)
diff --git a/sound/core/control_led.c b/sound/core/control_led.c index f975cc85772b..c88653c205eb 100644 --- a/sound/core/control_led.c +++ b/sound/core/control_led.c @@ -534,8 +534,7 @@ static ssize_t set_led_id(struct snd_ctl_led_card *led_card, const char *buf, si struct snd_ctl_elem_id id; int err;
- strncpy(buf2, buf, len); - buf2[len] = '\0'; + strncpy(buf2, buf, len + 1); memset(&id, 0, sizeof(id)); id.iface = SNDRV_CTL_ELEM_IFACE_MIXER; s = buf2;
On Mon, 09 Jan 2023 12:45:51 +0100, yang.yang29@zte.com.cn wrote:
From: Xu Panda xu.panda@zte.com.cn
The implementation of strscpy() is more robust and safer. That's now the recommended way to copy NUL-terminated strings.
Signed-off-by: Xu Panda xu.panda@zte.com.cn Signed-off-by: Yang Yang yang.yang29@zte.com.cn
sound/core/control_led.c | 3 +-- 1 file changed, 1 insertion(+), 2 deletions(-)
diff --git a/sound/core/control_led.c b/sound/core/control_led.c index f975cc85772b..c88653c205eb 100644 --- a/sound/core/control_led.c +++ b/sound/core/control_led.c @@ -534,8 +534,7 @@ static ssize_t set_led_id(struct snd_ctl_led_card *led_card, const char *buf, si struct snd_ctl_elem_id id; int err;
- strncpy(buf2, buf, len);
- buf2[len] = '\0';
- strncpy(buf2, buf, len + 1);
Still using strncpy()...?
thanks,
Takashi
On 09. 01. 23 13:40, Takashi Iwai wrote:
On Mon, 09 Jan 2023 12:45:51 +0100, yang.yang29@zte.com.cn wrote:
From: Xu Panda xu.panda@zte.com.cn
The implementation of strscpy() is more robust and safer. That's now the recommended way to copy NUL-terminated strings.
Signed-off-by: Xu Panda xu.panda@zte.com.cn Signed-off-by: Yang Yang yang.yang29@zte.com.cn
sound/core/control_led.c | 3 +-- 1 file changed, 1 insertion(+), 2 deletions(-)
diff --git a/sound/core/control_led.c b/sound/core/control_led.c index f975cc85772b..c88653c205eb 100644 --- a/sound/core/control_led.c +++ b/sound/core/control_led.c @@ -534,8 +534,7 @@ static ssize_t set_led_id(struct snd_ctl_led_card *led_card, const char *buf, si struct snd_ctl_elem_id id; int err;
- strncpy(buf2, buf, len);
- buf2[len] = '\0';
- strncpy(buf2, buf, len + 1);
Still using strncpy()...?
The original code should be:
diff --git a/sound/core/control_led.c b/sound/core/control_led.c index f975cc85772b..b44abefcb593 100644 --- a/sound/core/control_led.c +++ b/sound/core/control_led.c @@ -530,7 +530,7 @@ static ssize_t set_led_id(struct snd_ctl_led_card *led_card, const char *buf, si bool attach) { char buf2[256], *s, *os; - size_t len = max(sizeof(s) - 1, count); + size_t len = min(sizeof(buf2) - 1, count); struct snd_ctl_elem_id id; int err;
But it can be replaced with:
diff --git a/sound/core/control_led.c b/sound/core/control_led.c index f975cc85772b..41d4e898d34c 100644 --- a/sound/core/control_led.c +++ b/sound/core/control_led.c @@ -530,12 +530,11 @@ static ssize_t set_led_id(struct snd_ctl_led_card *led_card, const char *buf, si bool attach) { char buf2[256], *s, *os; - size_t len = max(sizeof(s) - 1, count); struct snd_ctl_elem_id id; int err;
- strncpy(buf2, buf, len); - buf2[len] = '\0'; + if (strscpy(buf2, buf, count) < 0) + return -E2BIG; memset(&id, 0, sizeof(id)); id.iface = SNDRV_CTL_ELEM_IFACE_MIXER; s = buf2;
I'll send a patch ASAP.
Jaroslav
-- Jaroslav Kysela perex@perex.cz Linux Sound Maintainer; ALSA Project; Red Hat, Inc.
Hi,
On Mon, Jan 9, 2023, at 20:45, yang.yang29@zte.com.cn wrote:
From: Xu Panda xu.panda@zte.com.cn
The implementation of strscpy() is more robust and safer. That's now the recommended way to copy NUL-terminated strings.
Signed-off-by: Xu Panda xu.panda@zte.com.cn Signed-off-by: Yang Yang yang.yang29@zte.com.cn
sound/core/control_led.c | 3 +-- 1 file changed, 1 insertion(+), 2 deletions(-)
diff --git a/sound/core/control_led.c b/sound/core/control_led.c index f975cc85772b..c88653c205eb 100644 --- a/sound/core/control_led.c +++ b/sound/core/control_led.c @@ -534,8 +534,7 @@ static ssize_t set_led_id(struct snd_ctl_led_card *led_card, const char *buf, si struct snd_ctl_elem_id id; int err;
- strncpy(buf2, buf, len);
- buf2[len] = '\0';
- strncpy(buf2, buf, len + 1);
The patch comment refers to strscpy(), however strncpy() is still used. I wonder whether it is the intension of this patch. I think any trouble happended.
Anyway I'm for usage of strscpy() as the comment.
memset(&id, 0, sizeof(id)); id.iface = SNDRV_CTL_ELEM_IFACE_MIXER; s = buf2; -- 2.15.2
As another issue, I can see that the local variable, len, can bring buffer overrun over buf2[256] since it has maximum value between the size of pointer and count argument. Maricious user space application can attack as long as it has write permission to the device attributes. I guess kernel stack can be broken by the attack.
``` 532 char buf2[256], *s, *os; 533 size_t len = max(sizeof(s) - 1, count); ... 537 strncpy(buf2, buf, len); ```
I'm already in bed today, so I hope anyone posts fix, or waiting tomorrow.
Regards
Takashi Sakamoto
participants (4)
-
Jaroslav Kysela -
Takashi Iwai -
Takashi Sakamoto -
yang.yang29＠zte.com.cn