2015-08-28 11:07:13

by Sasha Levin

Subject: [PATCH] tracepoint: don't make assumptions about length of string on task rename

While the dest comm string size is assured to be at least TASK_COMM_LEN long,
doing a memcpy() also adds the assumption that the source is at least that
long as well, which isn't assured, and isn't true in cases such as:

set_task_comm(worker->task, "kworker/dying");

This leads to accessing invalid memory.

Signed-off-by: Sasha Levin <[email protected]>
---
include/trace/events/task.h | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/include/trace/events/task.h b/include/trace/events/task.h
index dee3bb1..2cca6cd 100644
--- a/include/trace/events/task.h
+++ b/include/trace/events/task.h
@@ -46,7 +46,7 @@ TRACE_EVENT(task_rename,
TP_fast_assign(
__entry->pid = task->pid;
memcpy(entry->oldcomm, task->comm, TASK_COMM_LEN);
- memcpy(entry->newcomm, comm, TASK_COMM_LEN);
+ strlcpy(entry->newcomm, comm, TASK_COMM_LEN);
__entry->oom_score_adj = task->signal->oom_score_adj;
),

--
1.7.10.4

2015-08-28 15:02:55

by Steven Rostedt

Subject: Re: [PATCH] tracepoint: don't make assumptions about length of string on task rename

On Fri, 28 Aug 2015 07:06:58 -0400
Sasha Levin <[email protected]> wrote:

> While the dest comm string size is assured to be at least TASK_COMM_LEN long,
> doing a memcpy() also adds the assumption that the source is at least that
> long as well, which isn't assured, and isn't true in cases such as:
>
> set_task_comm(worker->task, "kworker/dying");
>
> This leads to accessing invalid memory.
>
> Signed-off-by: Sasha Levin <[email protected]>

Acked-by: Steven Rostedt <[email protected]>

Should this go to stable as well?

Also, as the memcpy was just faster than a strcpy, the static length
was used. Perhaps we should convert that to a dynamic length string.
But that should be a separate patch as this one fixes a possible bug,
and the conversion to a dynamic string is just an enhancement.

-- Steve


> ---
> include/trace/events/task.h | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/include/trace/events/task.h b/include/trace/events/task.h
> index dee3bb1..2cca6cd 100644
> --- a/include/trace/events/task.h
> +++ b/include/trace/events/task.h
> @@ -46,7 +46,7 @@ TRACE_EVENT(task_rename,
> TP_fast_assign(
> __entry->pid = task->pid;
> memcpy(entry->oldcomm, task->comm, TASK_COMM_LEN);
> - memcpy(entry->newcomm, comm, TASK_COMM_LEN);
> + strlcpy(entry->newcomm, comm, TASK_COMM_LEN);
> __entry->oom_score_adj = task->signal->oom_score_adj;
> ),
>