[13/55] fs/exec: replace strncpy with strscpy_pad in __get_task_comm

Commit Message

Andrew Morton Jan. 20, 2022, 2:08 a.m. UTC

From: Yafang Shao <[e-mail]>
Subject: fs/exec: replace strncpy with strscpy_pad in __get_task_comm

If the dest buffer size is smaller than sizeof(tsk->comm), the buffer will
be without null ternimator, that may cause problem.  Using strscpy_pad()
instead of strncpy() in __get_task_comm() can make the string always nul
ternimated and zero padded.

Link: https://lkml.kernel.org/r/[e-mail]
Suggested-by: Kees Cook <[e-mail]>
Suggested-by: Steven Rostedt <[e-mail]>
Signed-off-by: Yafang Shao <[e-mail]>
Reviewed-by: Kees Cook <[e-mail]>
Reviewed-by: David Hildenbrand <[e-mail]>
Cc: Mathieu Desnoyers <[e-mail]>
Cc: Arnaldo Carvalho de Melo <[e-mail]>
Cc: Alexei Starovoitov <[e-mail]>
Cc: Andrii Nakryiko <[e-mail]>
Cc: Michal Miroslaw <[e-mail]>
Cc: Peter Zijlstra <[e-mail]>
Cc: Steven Rostedt <[e-mail]>
Cc: Matthew Wilcox <[e-mail]>
Cc: David Hildenbrand <[e-mail]>
Cc: Al Viro <[e-mail]>
Cc: Kees Cook <[e-mail]>
Cc: Petr Mladek <[e-mail]>
Cc: Andrii Nakryiko <[e-mail]>
Cc: Dennis Dalessandro <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>
---

 fs/exec.c |    3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

Patch

--- a/fs/exec.c~fs-exec-replace-strncpy-with-strscpy_pad-in-__get_task_comm
+++ a/fs/exec.c
@@ -1207,7 +1207,8 @@  static int unshare_sighand(struct task_s
 char *__get_task_comm(char *buf, size_t buf_size, struct task_struct *tsk)
 {
 	task_lock(tsk);
-	strncpy(buf, tsk->comm, buf_size);
+	/* Always NUL terminated and zero-padded */
+	strscpy_pad(buf, tsk->comm, buf_size);
 	task_unlock(tsk);
 	return buf;
 }