[PATCH v2 1/7] fs/exec: replace strlcpy with strscpy_pad in __set_task_comm

[Yafang Shao]

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

Signed-off-by: Yafang Shao <laoar.shao@xxxxxxxxx>
Reviewed-by: Kees Cook <keescook@xxxxxxxxxxxx>
Reviewed-by: David Hildenbrand <david@xxxxxxxxxx>
Cc: Mathieu Desnoyers <mathieu.desnoyers@xxxxxxxxxxxx>
Cc: Arnaldo Carvalho de Melo <arnaldo.melo@xxxxxxxxx>
Cc: Alexei Starovoitov <alexei.starovoitov@xxxxxxxxx>
Cc: Andrii Nakryiko <andrii.nakryiko@xxxxxxxxx>
Cc: Michal Miroslaw <mirq-linux@xxxxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Steven Rostedt <rostedt@xxxxxxxxxxx>
Cc: Matthew Wilcox <willy@xxxxxxxxxxxxx>
Cc: David Hildenbrand <david@xxxxxxxxxx>
Cc: Al Viro <viro@xxxxxxxxxxxxxxxxxx>
Cc: Kees Cook <keescook@xxxxxxxxxxxx>
Cc: Petr Mladek <pmladek@xxxxxxxx>
---
 fs/exec.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/exec.c b/fs/exec.c
index 537d92c41105..51d3cb4e3cdf 100644
--- a/fs/exec.c
+++ b/fs/exec.c
@@ -1222,7 +1222,7 @@ void __set_task_comm(struct task_struct *tsk, const char *buf, bool exec)
 {
 	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);
 }
-- 
2.17.1