Messages in this thread | ![/](/images/icornerl.gif) | | Date | Tue, 24 Jan 2023 12:17:03 -0500 | From | Steven Rostedt <> | Subject | Re: [PATCH linux-next] tracing: use strscpy() to instead of strncpy() |
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On Mon, 9 Jan 2023 19:39:21 +0800 (CST) <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.
But the string being copied is *not* NUL-terminated! And this change causes a bug.
This is the 3rd patch I've seen that blindly converts strncpy() to strscpy() and causes a bug in doing so. Not very safe if you ask me.
> > Signed-off-by: Xu Panda <xu.panda@zte.com.cn> > Signed-off-by: Yang Yang <yang.yang29@zte.com.cn> > --- > kernel/trace/trace_events_synth.c | 3 +-- > 1 file changed, 1 insertion(+), 2 deletions(-) > > diff --git a/kernel/trace/trace_events_synth.c b/kernel/trace/trace_events_synth.c > index 67592eed0be8..cd636edd045e 100644 > --- a/kernel/trace/trace_events_synth.c > +++ b/kernel/trace/trace_events_synth.c > @@ -195,8 +195,7 @@ static int synth_field_string_size(char *type) > if (len == 0) > return 0; /* variable-length string */ > > - strncpy(buf, start, len); > - buf[len] = '\0'; > + strscpy(buf, start, len + 1); > > err = kstrtouint(buf, 0, &size); > if (err)
Here's the code being affected:
static int synth_field_string_size(char *type) { char buf[4], *end, *start; unsigned int len; int size, err;
start = strstr(type, "char["); if (start == NULL) return -EINVAL; start += sizeof("char[") - 1;
end = strchr(type, ']'); if (!end || end < start || type + strlen(type) > end + 1) return -EINVAL;
len = end - start; if (len > 3) return -EINVAL;
if (len == 0) return 0; /* variable-length string */
strncpy(buf, start, len); buf[len] = '\0';
And you are replacing the above two lines with just:
strscpy(buf, start, len + 1);
If you noticed, the string being placed into buf is:
"char[123]"
Where we want to copy that "123" into buf.
strscpy() expects the source to be nul terminated, or it will return -E2BIG.
So the above will *always* return -E2BIG *and* not end buf[] with '\0' as if strscpy() returns -E2BIG, then buf[] is not guaranteed to be NUL-terminated.
NACK!
-- Steve
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