Messages in this thread | | | From | Yafang Shao <> | Date | Thu, 14 Oct 2021 17:26:16 +0800 | Subject | Re: [PATCH v4 2/5] connector: use __get_task_comm in proc_comm_connector |
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On Thu, Oct 14, 2021 at 12:50 PM Kees Cook <keescook@chromium.org> wrote: > > On Wed, Oct 13, 2021 at 10:24:18PM -0400, Steven Rostedt wrote: > > On Thu, 14 Oct 2021 09:48:09 +0800 > > Yafang Shao <laoar.shao@gmail.com> wrote: > > > > > > __get_task_comm() uses strncpy() which my understanding is, does not add > > > > the nul terminating byte when truncating. Which changes the functionality > > > > here. As all task comms have a terminating byte, the old method would copy > > > > that and include it. This won't add the terminating byte if the buffer is > > > > smaller than the comm, and that might cause issues. > > > > > > > > > > Right, that is a problem. > > > It seems that we should add a new helper get_task_comm_may_truncated(). > > > > Or simply change __get_task_comm() to: > > > > char *__get_task_comm(char *buf, size_t buf_size, struct task_struct *tsk) > > { > > task_lock(tsk); > > strncpy(buf, tsk->comm, buf_size); > > /* The copied value is always nul terminated */ > > buf[buf_size - 1] = '\0'; > > task_unlock(tsk); > > return buf; > > } > > > > But that should probably be a separate patch. > > strscpy_pad() is the right thing here -- it'll retain the NUL-fill > properties of strncpy and terminate correctly. >
strscpy_pad() can also work, and seems more simple.
> The use of non-terminating issue with strncpy() wasn't a problem here > because get_task_comm() would always make sure task->comm was > terminated. (It uses strlcpy(), which I think needs to be changed to > strscpy_pad() too...) > > -- > Kees Cook
-- Thanks Yafang
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