On Mon, Jul 29, 2024 at 5:29 PM Jani Nikula [off-list ref] wrote:

On Mon, 29 Jul 2024, Yafang Shao [off-list ref] wrote:

quoted

Hello Andrew,

Is it appropriate for you to apply this to the mm tree?

Using {memcpy,strncpy,strcpy,kstrdup} to copy the task comm relies on the
length of task comm. Changes in the task comm could result in a destination
string that is overflow. Therefore, we should explicitly ensure the destination
string is always NUL-terminated, regardless of the task comm. This approach
will facilitate future extensions to the task comm.

Why are we normalizing calling double-underscore prefixed functions all
over the place? i.e. __get_task_comm().

get_task_comm() is widely used. At a glance, looks like it could be used
in many of the patches here too.

There is a BUILD_BUG_ON() inside get_task_comm(), so when you use
get_task_comm(), it implies that the BUILD_BUG_ON() is necessary.
However, we don't want to impose this restriction on code where the
length can be dynamically changed.

One use case of get_task_comm() is in code that has already exposed
the length to userspace. In such cases, we specifically add the
BUILD_BUG_ON() to prevent developers from changing it. For more
information, see commit 95af469c4f60 ("fs/binfmt_elf: replace
open-coded string copy with get_task_comm").

-- 
Regards
Yafang