[patch 12/55] fs/exec: replace strlcpy with strscpy_pad in __set_task_comm

[Andrew Morton <akpm@linux-foundation.org>]

From: Yafang Shao <laoar.shao@gmail.com>
Subject: fs/exec: replace strlcpy with strscpy_pad in __set_task_comm

Patch series "task comm cleanups", v2.

This patchset is part of the patchset "extend task comm from 16 to 24"[1].
Now we have different opinion that dynamically allocates memory to store
kthread's long name into a separate pointer, so I decide to take the
useful cleanups apart from the original patchset and send it
separately[2].

These useful cleanups can make the usage around task comm less
error-prone.  Furthermore, it will be useful if we want to extend task
comm in the future.

[1]. https://lore.kernel.org/lkml/20211101060419.4682-1-laoar.shao@gmail.com/
[2]. https://lore.kernel.org/lkml/CALOAHbAx55AUo3bm8ZepZSZnw7A08cvKPdPyNTf=E_tPqmw5hw@mail.gmail.com/


This patch (of 7):

strlcpy() can trigger out-of-bound reads on the source string[1], we'd
better use strscpy() instead.  To make it be robust against full tsk->comm
copies that got noticed in other places, we should make sure it's zero
padded.

[1] https://github.com/KSPP/linux/issues/89

Link: https://lkml.kernel.org/r/20211120112738.45980-1-laoar.shao@gmail.com
Link: https://lkml.kernel.org/r/20211120112738.45980-2-laoar.shao@gmail.com
Signed-off-by: Yafang Shao <laoar.shao@gmail.com>
Reviewed-by: Kees Cook <keescook@chromium.org>
Reviewed-by: David Hildenbrand <david@redhat.com>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Arnaldo Carvalho de Melo <arnaldo.melo@gmail.com>
Cc: Alexei Starovoitov <alexei.starovoitov@gmail.com>
Cc: Andrii Nakryiko <andrii.nakryiko@gmail.com>
Cc: Michal Miroslaw <mirq-linux@rere.qmqm.pl>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: David Hildenbrand <david@redhat.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Kees Cook <keescook@chromium.org>
Cc: Petr Mladek <pmladek@suse.com>
Cc: Andrii Nakryiko <andrii@kernel.org>
Cc: Dennis Dalessandro <dennis.dalessandro@cornelisnetworks.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 fs/exec.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/fs/exec.c~fs-exec-replace-strlcpy-with-strscpy_pad-in-__set_task_comm
+++ a/fs/exec.c
@@ -1222,7 +1222,7 @@ void __set_task_comm(struct task_struct
 {
 	task_lock(tsk);
 	trace_task_rename(tsk, buf);
-	strlcpy(tsk->comm, buf, sizeof(tsk->comm));
+	strscpy_pad(tsk->comm, buf, sizeof(tsk->comm));
 	task_unlock(tsk);
 	perf_event_comm(tsk, exec);
 }
_