2021-12-09 02:14:24

by Jiasheng Jiang

Subject: [PATCH] net: sched: gred: potential dereference of null pointer

The return value of kzalloc() needs to be checked.
To avoid use of null pointer in gred_change_vq() in case
of the failure of alloc.

Fixes: 869aa41044b0 ("sch_gred: prefer GFP_KERNEL allocations")
Signed-off-by: Jiasheng Jiang <[email protected]>
---
net/sched/sch_gred.c | 2 ++
1 file changed, 2 insertions(+)

diff --git a/net/sched/sch_gred.c b/net/sched/sch_gred.c
index f4132dc25ac0..c0d355281baf 100644
--- a/net/sched/sch_gred.c
+++ b/net/sched/sch_gred.c
@@ -697,6 +697,8 @@ static int gred_change(struct Qdisc *sch, struct nlattr *opt,
}

prealloc = kzalloc(sizeof(*prealloc), GFP_KERNEL);
+ if (!prealloc)
+ return -ENOMEM;
sch_tree_lock(sch);

err = gred_change_vq(sch, ctl->DP, ctl, prio, stab, max_P, &prealloc,
--
2.25.1

2021-12-09 02:36:15

by Jakub Kicinski

Subject: Re: [PATCH] net: sched: gred: potential dereference of null pointer

On Thu, 9 Dec 2021 10:13:46 +0800 Jiasheng Jiang wrote:
> The return value of kzalloc() needs to be checked.
> To avoid use of null pointer in gred_change_vq() in case
> of the failure of alloc.
>
> Fixes: 869aa41044b0 ("sch_gred: prefer GFP_KERNEL allocations")
> Signed-off-by: Jiasheng Jiang <[email protected]>

I don't see how. Please explain in more detail. gred_change_vq() gets
a pointer to a pointer and checks if its values is NULL.

> diff --git a/net/sched/sch_gred.c b/net/sched/sch_gred.c
> index f4132dc25ac0..c0d355281baf 100644
> --- a/net/sched/sch_gred.c
> +++ b/net/sched/sch_gred.c
> @@ -697,6 +697,8 @@ static int gred_change(struct Qdisc *sch, struct nlattr *opt,
> }
>
> prealloc = kzalloc(sizeof(*prealloc), GFP_KERNEL);
> + if (!prealloc)
> + return -ENOMEM;
> sch_tree_lock(sch);
>
> err = gred_change_vq(sch, ctl->DP, ctl, prio, stab, max_P, &prealloc,