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Date:   Mon, 20 Apr 2020 15:33:52 -0700
From:   Andrew Morton <akpm@linux-foundation.org>
To:     glider@google.com
Cc:     adobriyan@gmail.com, linux-kernel@vger.kernel.org,
        sunhaoyl@outlook.com, Kees Cook <keescook@chromium.org>
Subject: Re: [PATCH] fs/binfmt_elf.c: allocate initialized memory in
 fill_thread_core_info()
Message-Id: <20200420153352.6682533e794f591dae7aafbc@linux-foundation.org>
In-Reply-To: <20200419100848.63472-1-glider@google.com>
References: <20200419100848.63472-1-glider@google.com>
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On Sun, 19 Apr 2020 12:08:48 +0200 glider@google.com wrote:

> KMSAN reported uninitialized data being written to disk when dumping
> core. As a result, several kilobytes of kmalloc memory may be written to
> the core file and then read by a non-privileged user.
> 
> ...
>
> --- a/fs/binfmt_elf.c
> +++ b/fs/binfmt_elf.c
> @@ -1733,7 +1733,7 @@ static int fill_thread_core_info(struct elf_thread_core_info *t,
>  		    (!regset->active || regset->active(t->task, regset) > 0)) {
>  			int ret;
>  			size_t size = regset_size(t->task, regset);
> -			void *data = kmalloc(size, GFP_KERNEL);
> +			void *data = kzalloc(size, GFP_KERNEL);
>  			if (unlikely(!data))
>  				return 0;
>  			ret = regset->get(t->task, regset,

This seems to be a quite easy way of exposing quite a large amount of
kernel memory contents, so I think I'll add a cc:stable to this patch?