linux-kernel - Re: [PATCH v3] proc/kcore: fix invalid memory access in multi-page read optimization

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Date:   Tue, 4 Sep 2018 15:41:50 -0700
From:   Omar Sandoval <osandov@...ndov.com>
To:     Dominique Martinet <asmadeus@...ewreck.org>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org,
        Alexey Dobriyan <adobriyan@...il.com>,
        Eric Biederman <ebiederm@...ssion.com>,
        James Morse <james.morse@....com>,
        Bhupesh Sharma <bhsharma@...hat.com>, kernel-team@...com
Subject: Re: [PATCH v3] proc/kcore: fix invalid memory access in multi-page
 read optimization

On Wed, Sep 05, 2018 at 12:38:22AM +0200, Dominique Martinet wrote:
> The 'm' kcore_list item could point to kclist_head, and it is incorrect to
> look at m->addr / m->size in this case.
> There is no choice but to run through the list of entries for every address
> if we did not find any entry in the previous iteration
> 
> Reset 'm' to NULL in that case at Omar Sandoval's suggestion.
> 
> Fixes: bf991c2231117 ("proc/kcore: optimize multiple page reads")

Reviewed-by: Omar Sandoval <osandov@...com>

Thanks again for catching this!

> Signed-off-by: Dominique Martinet <asmadeus@...ewreck.org>
> ---
> 
> Sorry, resent v2 because From didn't match sob tag
> 
>  fs/proc/kcore.c | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/fs/proc/kcore.c b/fs/proc/kcore.c
> index ad72261ee3fe..578926032880 100644
> --- a/fs/proc/kcore.c
> +++ b/fs/proc/kcore.c
> @@ -464,6 +464,7 @@ read_kcore(struct file *file, char __user *buffer, size_t buflen, loff_t *fpos)
>  				ret = -EFAULT;
>  				goto out;
>  			}
> +			m = NULL;
>  		} else if (m->type == KCORE_VMALLOC) {
>  			vread(buf, (char *)start, tsz);
>  			/* we have to zero-fill user buffer even if no read */
> -- 
> 2.17.1
>