2021-11-08 10:18:57

by Yafang Shao

Subject: [PATCH 2/7] fs/exec: make __get_task_comm always get a nul terminated string

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.

Suggested-by: Kees Cook <[email protected]>
Suggested-by: Steven Rostedt <[email protected]>
Signed-off-by: Yafang Shao <[email protected]>
Reviewed-by: Kees Cook <[email protected]>
Cc: Mathieu Desnoyers <[email protected]>
Cc: Arnaldo Carvalho de Melo <[email protected]>
Cc: Alexei Starovoitov <[email protected]>
Cc: Andrii Nakryiko <[email protected]>
Cc: Michal Miroslaw <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Steven Rostedt <[email protected]>
Cc: Matthew Wilcox <[email protected]>
Cc: David Hildenbrand <[email protected]>
Cc: Al Viro <[email protected]>
Cc: Kees Cook <[email protected]>
Cc: Petr Mladek <[email protected]>
---
fs/exec.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/fs/exec.c b/fs/exec.c
index 404156b5b314..013b707d995d 100644
--- a/fs/exec.c
+++ b/fs/exec.c
@@ -1209,7 +1209,8 @@ static int unshare_sighand(struct task_struct *me)
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;
}
--
2.17.1

2021-11-11 10:00:11

by David Hildenbrand

Subject: Re: [PATCH 2/7] fs/exec: make __get_task_comm always get a nul terminated string

On 08.11.21 09:38, Yafang Shao wrote:
> 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.
>
> Suggested-by: Kees Cook <[email protected]>
> Suggested-by: Steven Rostedt <[email protected]>
> Signed-off-by: Yafang Shao <[email protected]>
> Reviewed-by: Kees Cook <[email protected]>
> Cc: Mathieu Desnoyers <[email protected]>
> Cc: Arnaldo Carvalho de Melo <[email protected]>
> Cc: Alexei Starovoitov <[email protected]>
> Cc: Andrii Nakryiko <[email protected]>
> Cc: Michal Miroslaw <[email protected]>
> Cc: Peter Zijlstra <[email protected]>
> Cc: Steven Rostedt <[email protected]>
> Cc: Matthew Wilcox <[email protected]>
> Cc: David Hildenbrand <[email protected]>
> Cc: Al Viro <[email protected]>
> Cc: Kees Cook <[email protected]>
> Cc: Petr Mladek <[email protected]>
> ---

Reviewed-by: David Hildenbrand <[email protected]>


--
Thanks,

David / dhildenb