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SubjectRe: [PATCH] net: xfrm: Fix potential oops in xfrm_user_rcv_msg and array out of bounds
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On 2019/3/5 15:31, Steffen Klassert wrote:
> On Tue, Mar 05, 2019 at 03:08:49PM +0800, Su Yanjun <suyj.fnst@cn.fujitsu.com> wrote:
>> On 2019/3/5 14:49, Herbert Xu wrote:
>>
>>> On Sun, Mar 03, 2019 at 10:47:39PM -0500, Su Yanjun wrote:
>>>> When i review xfrm_user.c code, i found some potentical bug in it.
>>>>
>>>> In xfrm_user_rcvmsg if type parameter from user space is set to
>>>> XFRM_MSG_MAX or XFRM_MSG_NEWSADINFO or XFRM_MSG_NEWSPDINFO. It will cause
>>>> xfrm_user_rcv_msg referring to null entry in xfrm_dispatch array.
>>>>
>>>> Signed-off-by: Su Yanjun <suyj.fnst@cn.fujitsu.com>
>>>> ---
>>>> net/xfrm/xfrm_user.c | 4 +++-
>>>> 1 file changed, 3 insertions(+), 1 deletion(-)
>>>>
>>>> diff --git a/net/xfrm/xfrm_user.c b/net/xfrm/xfrm_user.c
>>>> index a131f9f..d832783 100644
>>>> --- a/net/xfrm/xfrm_user.c
>>>> +++ b/net/xfrm/xfrm_user.c
>>>> @@ -2630,11 +2630,13 @@ static int xfrm_user_rcv_msg(struct sk_buff *skb, struct nlmsghdr *nlh,
>>>> return -EOPNOTSUPP;
>>>> type = nlh->nlmsg_type;
>>>> - if (type > XFRM_MSG_MAX)
>>>> + if (type >= XFRM_MSG_MAX)
>>>> return -EINVAL;
>>> Your patch is wrong. Please check the definition of XFRM_MSG_MAX.
>> I see, thanks for your reply.
>>
>> type -= XFRM_MSG_BASE;
>> link = &xfrm_dispatch[type];
>> + if (!link)
>> + return -EOPNOTSUPP;
>>
>> Here **link** may refer to null entry for special types such as
>> XFRM_MSG_MAX or XFRM_MSG_NEWSADINFO or XFRM_MSG_NEWSPDINFO
>> Am i miss something?
> 'link' is always a valid pointer into that array.

Thanks

Su



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