linux-kernel - Re: [RFC PATCH] mm/mempolicy: Fix memory leak in set_mempolicy_home

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Date:   Wed, 14 Dec 2022 15:16:22 -0800
From:   Randy Dunlap <rdunlap@...radead.org>
To:     Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
        Andrew Morton <akpm@...ux-foundation.org>
Cc:     linux-kernel@...r.kernel.org,
        "Aneesh Kumar K . V" <aneesh.kumar@...ux.ibm.com>,
        Ben Widawsky <ben.widawsky@...el.com>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Feng Tang <feng.tang@...el.com>,
        Michal Hocko <mhocko@...nel.org>,
        Andrea Arcangeli <aarcange@...hat.com>,
        Mel Gorman <mgorman@...hsingularity.net>,
        Mike Kravetz <mike.kravetz@...cle.com>,
        Vlastimil Babka <vbabka@...e.cz>,
        Andi Kleen <ak@...ux.intel.com>,
        Dan Williams <dan.j.williams@...el.com>,
        Huang Ying <ying.huang@...el.com>, linux-api@...r.kernel.org,
        stable@...r.kernel.org
Subject: Re: [RFC PATCH] mm/mempolicy: Fix memory leak in
 set_mempolicy_home_node system call



On 12/14/22 14:21, Mathieu Desnoyers wrote:
> When encountering any vma in the range with policy other than MPOL_BIND
> or MPOL_PREFERRED_MANY, an error is returned without issuing a mpol_put
> on the policy just allocated with mpol_dup().
> 
> This allows arbitrary users to leak kernel memory.
> 
> Fixes: c6018b4b2549 ("mm/mempolicy: add set_mempolicy_home_node syscall")
> Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@...icios.com>
> Cc: Aneesh Kumar K.V <aneesh.kumar@...ux.ibm.com>
> Cc: Ben Widawsky <ben.widawsky@...el.com>
> Cc: Dave Hansen <dave.hansen@...ux.intel.com>
> Cc: Feng Tang <feng.tang@...el.com>
> Cc: Michal Hocko <mhocko@...nel.org>
> Cc: Andrea Arcangeli <aarcange@...hat.com>
> Cc: Mel Gorman <mgorman@...hsingularity.net>
> Cc: Mike Kravetz <mike.kravetz@...cle.com>
> Cc: Randy Dunlap <rdunlap@...radead.org>
> Cc: Vlastimil Babka <vbabka@...e.cz>
> Cc: Andi Kleen <ak@...ux.intel.com>
> Cc: Dan Williams <dan.j.williams@...el.com>
> Cc: Huang Ying <ying.huang@...el.com>
> Cc: <linux-api@...r.kernel.org>
> Cc: Andrew Morton <akpm@...ux-foundation.org>
> Cc: stable@...r.kernel.org # 5.17+

Reviewed-by: Randy Dunlap <rdunlap@...radead.org>

Thanks.

> ---
>  mm/mempolicy.c | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/mm/mempolicy.c b/mm/mempolicy.c
> index 61aa9aedb728..02c8a712282f 100644
> --- a/mm/mempolicy.c
> +++ b/mm/mempolicy.c
> @@ -1540,6 +1540,7 @@ SYSCALL_DEFINE4(set_mempolicy_home_node, unsigned long, start, unsigned long, le
>  		 * the home node for vmas we already updated before.
>  		 */
>  		if (new->mode != MPOL_BIND && new->mode != MPOL_PREFERRED_MANY) {
> +			mpol_put(new);
>  			err = -EOPNOTSUPP;
>  			break;
>  		}

-- 
~Randy