# Re: \[PATCH 1/1\] mm/madvise: replace ptrace attach requirement for process\_madvise

- From: Florian Weimer \<hidden\>
- Date: 2021-01-11 10:21:38 
- List: linux-api
- Page: https://ratatoskr.run/linux-api/2021/01/6229410
- Thread: https://ratatoskr.run/linux-mm/2021/01/6229410/t.md

```text
* Suren Baghdasaryan:

> diff --git a/mm/madvise.c b/mm/madvise.c
> index 6a660858784b..c2d600386902 100644
> --- a/mm/madvise.c
> +++ b/mm/madvise.c
> @@ -1197,12 +1197,22 @@ SYSCALL_DEFINE5(process_madvise, int, pidfd, const struct iovec __user *, vec,
>  		goto release_task;
>  	}
>  
> -	mm = mm_access(task, PTRACE_MODE_ATTACH_FSCREDS);
> +	/* Require PTRACE_MODE_READ to avoid leaking ASLR metadata. */
> +	mm = mm_access(task, PTRACE_MODE_READ_FSCREDS);
>  	if (IS_ERR_OR_NULL(mm)) {
>  		ret = IS_ERR(mm) ? PTR_ERR(mm) : -ESRCH;
>  		goto release_task;
>  	}

Shouldn't this depend on the requested behavior?  Several operations
directly result in observable changes, and go beyond performance tuning.

Thanks,
Florian
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```