2019-07-25 16:04:03

by Jia-Ju Bai

Subject: [PATCH] net: tipc: Fix a possible null-pointer dereference in tipc_publ_purge()

In tipc_publ_purge(), there is an if statement on 215 to
check whether p is NULL:
if (p)

When p is NULL, it is used on line 226:
kfree_rcu(p, rcu);

Thus, a possible null-pointer dereference may occur.

To fix this bug, p is checked before being used.

This bug is found by a static analysis tool STCheck written by us.

Signed-off-by: Jia-Ju Bai <[email protected]>
---
net/tipc/name_distr.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/net/tipc/name_distr.c b/net/tipc/name_distr.c
index 44abc8e9c990..241ed2274473 100644
--- a/net/tipc/name_distr.c
+++ b/net/tipc/name_distr.c
@@ -223,7 +223,8 @@ static void tipc_publ_purge(struct net *net, struct publication *publ, u32 addr)
publ->key);
}

- kfree_rcu(p, rcu);
+ if (p)
+ kfree_rcu(p, rcu);
}

/**
--
2.17.0

2019-07-26 14:23:16

by Ying Xue

Subject: Re: [PATCH] net: tipc: Fix a possible null-pointer dereference in tipc_publ_purge()

On 7/25/19 5:20 PM, Jia-Ju Bai wrote:
> In tipc_publ_purge(), there is an if statement on 215 to
> check whether p is NULL:
> if (p)
>
> When p is NULL, it is used on line 226:
> kfree_rcu(p, rcu);
>
> Thus, a possible null-pointer dereference may occur.
>
> To fix this bug, p is checked before being used.
>
> This bug is found by a static analysis tool STCheck written by us.
>
> Signed-off-by: Jia-Ju Bai <[email protected]>
> ---
> net/tipc/name_distr.c | 3 ++-
> 1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/net/tipc/name_distr.c b/net/tipc/name_distr.c
> index 44abc8e9c990..241ed2274473 100644
> --- a/net/tipc/name_distr.c
> +++ b/net/tipc/name_distr.c
> @@ -223,7 +223,8 @@ static void tipc_publ_purge(struct net *net, struct publication *publ, u32 addr)
> publ->key);
> }
>
> - kfree_rcu(p, rcu);
> + if (p)

No, I don't think so because kfree_rcu() will internally check if "p"
pointer is NULL or not.

> + kfree_rcu(p, rcu);
> }
>
> /**
>

2019-07-26 21:06:06

by David Miller

Subject: Re: [PATCH] net: tipc: Fix a possible null-pointer dereference in tipc_publ_purge()

From: Jia-Ju Bai <[email protected]>
Date: Thu, 25 Jul 2019 17:20:21 +0800

> @@ -223,7 +223,8 @@ static void tipc_publ_purge(struct net *net, struct publication *publ, u32 addr)
> publ->key);
> }
>
> - kfree_rcu(p, rcu);
> + if (p)
> + kfree_rcu(p, rcu);

Please fix your automated tools if that is what found this, because as
others have nodes kfree_rcu() can take a NULL pointer argument just
fine.

Thank you.