Le lun. 22 févr. 2021 à 18:49, Steven Rostedt <rostedt@xxxxxxxxxxx> a écrit :
> - if (unlikely(!maxlen))
> - return -ENOMEM;
Don't remove the above. You just broke the else side.
> -
> - if (addr == FETCH_TOKEN_COMM)
> - ret = strlcpy(dst, current->comm, maxlen);
> - else
> + if (addr == FETCH_TOKEN_COMM) {
> + ret = strscpy(dst, current->comm, maxlen);
> + if (ret == -E2BIG)
> + return -ENOMEM;
I'm not sure the above is what we want. current->comm is always nul
terminated, and not only that, it will never be bigger than TASK_COMM_LEN.
If the "dst" location is smaller than comm (maxlen < TASK_COMM_LEN), it is
still OK to copy a partial string. It should not return -ENOMEM which looks
to be what happens with this patch.
In other words, it looks like this patch breaks the current code in more
ways than one.
-- Steve
Hello,
Mhhh, *I think* that I had an issue during rebase, I don't remember to have removed the " if (unlikely(!maxlen))" (sorry for that).
Well, strscpy always returns a truncated string even in case of possible overflow, the function copies what it can in "dst", it will just return -E2BIG when
it does not fit or when "count" has a bad value (zero or > INT_MAX). We have just to make a difference between "-E2BIG, data has been copied to dst and it is truncated" and "-E2BIG, possible wrong size passed as argument".
I agree that it needs at least to work like before, and I think we can preserve the old behaviour even with strscpy (we just need to adapt the error handling accordingly).
I will fix this in v2.
Thanks,
Romain
