* [PATCH 1/2] net: ipv4: Fix a possible null-pointer dereference in inet_csk_rebuild_route()
@ 2019-07-26 2:25 Jia-Ju Bai
2019-07-26 9:15 ` Nicolas Dichtel
2019-07-27 20:25 ` David Miller
0 siblings, 2 replies; 3+ messages in thread
From: Jia-Ju Bai @ 2019-07-26 2:25 UTC (permalink / raw)
To: davem, kuznet, yoshfuji; +Cc: netdev, linux-kernel, Jia-Ju Bai
In inet_csk_rebuild_route(), rt is assigned to NULL on line 1071.
On line 1076, rt is used:
return &rt->dst;
Thus, a possible null-pointer dereference may occur.
To fix this bug, rt is checked before being used.
This bug is found by a static analysis tool STCheck written by us.
Signed-off-by: Jia-Ju Bai <baijiaju1990@gmail.com>
---
net/ipv4/inet_connection_sock.c | 5 ++++-
1 file changed, 4 insertions(+), 1 deletion(-)
diff --git a/net/ipv4/inet_connection_sock.c b/net/ipv4/inet_connection_sock.c
index f5c163d4771b..27d9d80f3401 100644
--- a/net/ipv4/inet_connection_sock.c
+++ b/net/ipv4/inet_connection_sock.c
@@ -1073,7 +1073,10 @@ static struct dst_entry *inet_csk_rebuild_route(struct sock *sk, struct flowi *f
sk_setup_caps(sk, &rt->dst);
rcu_read_unlock();
- return &rt->dst;
+ if (rt)
+ return &rt->dst;
+ else
+ return NULL;
}
struct dst_entry *inet_csk_update_pmtu(struct sock *sk, u32 mtu)
--
2.17.0
^ permalink raw reply related [flat|nested] 3+ messages in thread
* Re: [PATCH 1/2] net: ipv4: Fix a possible null-pointer dereference in inet_csk_rebuild_route()
2019-07-26 2:25 [PATCH 1/2] net: ipv4: Fix a possible null-pointer dereference in inet_csk_rebuild_route() Jia-Ju Bai
@ 2019-07-26 9:15 ` Nicolas Dichtel
2019-07-27 20:25 ` David Miller
1 sibling, 0 replies; 3+ messages in thread
From: Nicolas Dichtel @ 2019-07-26 9:15 UTC (permalink / raw)
To: Jia-Ju Bai, davem, kuznet, yoshfuji; +Cc: netdev, linux-kernel
Le 26/07/2019 à 04:25, Jia-Ju Bai a écrit :
> In inet_csk_rebuild_route(), rt is assigned to NULL on line 1071.
> On line 1076, rt is used:
> return &rt->dst;
> Thus, a possible null-pointer dereference may occur.>
> To fix this bug, rt is checked before being used.
>
> This bug is found by a static analysis tool STCheck written by us.
>
> Signed-off-by: Jia-Ju Bai <baijiaju1990@gmail.com>
> ---
> net/ipv4/inet_connection_sock.c | 5 ++++-
> 1 file changed, 4 insertions(+), 1 deletion(-)
>
> diff --git a/net/ipv4/inet_connection_sock.c b/net/ipv4/inet_connection_sock.c
> index f5c163d4771b..27d9d80f3401 100644
> --- a/net/ipv4/inet_connection_sock.c
> +++ b/net/ipv4/inet_connection_sock.c
> @@ -1073,7 +1073,10 @@ static struct dst_entry *inet_csk_rebuild_route(struct sock *sk, struct flowi *f
> sk_setup_caps(sk, &rt->dst);
> rcu_read_unlock();
>
> - return &rt->dst;
> + if (rt)
> + return &rt->dst;
> + else
> + return NULL;
Hmm, ->dst is the first field (and that will never change), thus &rt->dst is
NULL if rt is NULL.
I don't think there is a problem with the current code.
Regards,
Nicolas
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [PATCH 1/2] net: ipv4: Fix a possible null-pointer dereference in inet_csk_rebuild_route()
2019-07-26 2:25 [PATCH 1/2] net: ipv4: Fix a possible null-pointer dereference in inet_csk_rebuild_route() Jia-Ju Bai
2019-07-26 9:15 ` Nicolas Dichtel
@ 2019-07-27 20:25 ` David Miller
1 sibling, 0 replies; 3+ messages in thread
From: David Miller @ 2019-07-27 20:25 UTC (permalink / raw)
To: baijiaju1990; +Cc: kuznet, yoshfuji, netdev, linux-kernel
From: Jia-Ju Bai <baijiaju1990@gmail.com>
Date: Fri, 26 Jul 2019 10:25:34 +0800
> diff --git a/net/ipv4/inet_connection_sock.c b/net/ipv4/inet_connection_sock.c
> index f5c163d4771b..27d9d80f3401 100644
> --- a/net/ipv4/inet_connection_sock.c
> +++ b/net/ipv4/inet_connection_sock.c
> @@ -1073,7 +1073,10 @@ static struct dst_entry *inet_csk_rebuild_route(struct sock *sk, struct flowi *f
> sk_setup_caps(sk, &rt->dst);
> rcu_read_unlock();
>
> - return &rt->dst;
> + if (rt)
> + return &rt->dst;
> + else
> + return NULL;
If rt is NULL, &rt->dst is also NULL as has been pointed out to you.
Please fix your automated tools to understand this case before submitting
more changes.
Thank you.
^ permalink raw reply [flat|nested] 3+ messages in thread
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2019-07-26 2:25 [PATCH 1/2] net: ipv4: Fix a possible null-pointer dereference in inet_csk_rebuild_route() Jia-Ju Bai
2019-07-26 9:15 ` Nicolas Dichtel
2019-07-27 20:25 ` David Miller
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