2022-09-17 03:12:43

by Li Zhong

Subject: [PATCH v1] net/ipv4/nexthop: check the return value of nexthop_find_by_id()

Check the return value of nexthop_find_by_id(), which could be NULL on
when not found. So we check to avoid null pointer dereference.

Signed-off-by: Li Zhong <[email protected]>
---
net/ipv4/nexthop.c | 4 ++++
1 file changed, 4 insertions(+)

diff --git a/net/ipv4/nexthop.c b/net/ipv4/nexthop.c
index 853a75a8fbaf..9f91bb78eed5 100644
--- a/net/ipv4/nexthop.c
+++ b/net/ipv4/nexthop.c
@@ -2445,6 +2445,10 @@ static struct nexthop *nexthop_create_group(struct net *net,
struct nh_info *nhi;

nhe = nexthop_find_by_id(net, entry[i].id);
+ if (!nhe) {
+ err = -EINVAL;
+ goto out_no_nh;
+ }
if (!nexthop_get(nhe)) {
err = -ENOENT;
goto out_no_nh;
--
2.25.1

2022-09-17 08:43:44

by Nikolay Aleksandrov

Subject: Re: [PATCH v1] net/ipv4/nexthop: check the return value of nexthop_find_by_id()

On 17/09/2022 05:30, Li Zhong wrote:
> Check the return value of nexthop_find_by_id(), which could be NULL on
> when not found. So we check to avoid null pointer dereference.
>
> Signed-off-by: Li Zhong <[email protected]>
> ---
> net/ipv4/nexthop.c | 4 ++++
> 1 file changed, 4 insertions(+)
>
> diff --git a/net/ipv4/nexthop.c b/net/ipv4/nexthop.c
> index 853a75a8fbaf..9f91bb78eed5 100644
> --- a/net/ipv4/nexthop.c
> +++ b/net/ipv4/nexthop.c
> @@ -2445,6 +2445,10 @@ static struct nexthop *nexthop_create_group(struct net *net,
> struct nh_info *nhi;
>
> nhe = nexthop_find_by_id(net, entry[i].id);
> + if (!nhe) {
> + err = -EINVAL;
> + goto out_no_nh;
> + }
> if (!nexthop_get(nhe)) {
> err = -ENOENT;
> goto out_no_nh;

These are validated in nh_check_attr_group() and should exist at this point.
Since remove_nexthop() should run under rtnl I don't see a way for a nexthop
to disappear after nh_check_attr_group() and before nexthop_create_group().

Did you notice a problem or have a stack dump?

2022-09-17 15:03:45

by David Ahern

Subject: Re: [PATCH v1] net/ipv4/nexthop: check the return value of nexthop_find_by_id()

On 9/17/22 2:29 AM, Nikolay Aleksandrov wrote:
> On 17/09/2022 05:30, Li Zhong wrote:
>> Check the return value of nexthop_find_by_id(), which could be NULL on
>> when not found. So we check to avoid null pointer dereference.
>>
>> Signed-off-by: Li Zhong <[email protected]>
>> ---
>> net/ipv4/nexthop.c | 4 ++++
>> 1 file changed, 4 insertions(+)
>>
>> diff --git a/net/ipv4/nexthop.c b/net/ipv4/nexthop.c
>> index 853a75a8fbaf..9f91bb78eed5 100644
>> --- a/net/ipv4/nexthop.c
>> +++ b/net/ipv4/nexthop.c
>> @@ -2445,6 +2445,10 @@ static struct nexthop *nexthop_create_group(struct net *net,
>> struct nh_info *nhi;
>>
>> nhe = nexthop_find_by_id(net, entry[i].id);
>> + if (!nhe) {
>> + err = -EINVAL;
>> + goto out_no_nh;
>> + }
>> if (!nexthop_get(nhe)) {
>> err = -ENOENT;
>> goto out_no_nh;
>
> These are validated in nh_check_attr_group() and should exist at this point.
> Since remove_nexthop() should run under rtnl I don't see a way for a nexthop
> to disappear after nh_check_attr_group() and before nexthop_create_group().
>

exactly. That lookup can't fail because the ids have been validated and
all of this is under rtnl preventing nexthop removes.

2022-09-18 02:16:39

by Li Zhong

Subject: Re: [PATCH v1] net/ipv4/nexthop: check the return value of nexthop_find_by_id()

On Sat, Sep 17, 2022 at 7:46 AM David Ahern <[email protected]> wrote:
>
> On 9/17/22 2:29 AM, Nikolay Aleksandrov wrote:
> > On 17/09/2022 05:30, Li Zhong wrote:
> >> Check the return value of nexthop_find_by_id(), which could be NULL on
> >> when not found. So we check to avoid null pointer dereference.
> >>
> >> Signed-off-by: Li Zhong <[email protected]>
> >> ---
> >> net/ipv4/nexthop.c | 4 ++++
> >> 1 file changed, 4 insertions(+)
> >>
> >> diff --git a/net/ipv4/nexthop.c b/net/ipv4/nexthop.c
> >> index 853a75a8fbaf..9f91bb78eed5 100644
> >> --- a/net/ipv4/nexthop.c
> >> +++ b/net/ipv4/nexthop.c
> >> @@ -2445,6 +2445,10 @@ static struct nexthop *nexthop_create_group(struct net *net,
> >> struct nh_info *nhi;
> >>
> >> nhe = nexthop_find_by_id(net, entry[i].id);
> >> + if (!nhe) {
> >> + err = -EINVAL;
> >> + goto out_no_nh;
> >> + }
> >> if (!nexthop_get(nhe)) {
> >> err = -ENOENT;
> >> goto out_no_nh;
> >
> > These are validated in nh_check_attr_group() and should exist at this point.
> > Since remove_nexthop() should run under rtnl I don't see a way for a nexthop
> > to disappear after nh_check_attr_group() and before nexthop_create_group().
> >
>
> exactly. That lookup can't fail because the ids have been validated and
> all of this is under rtnl preventing nexthop removes.
>

Thanks for all your replies. That makes sense to me.