netdev - Re: [PATCH][next] net: sched: cls_u32: Fix allocation in u32

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Message-ID: <CAM0EoMmK0VK1=5SSHVm28zz2CUCamxJPXNukehqY955uP17VPQ@mail.gmail.com>
Date: Thu, 17 Aug 2023 12:32:31 -0400
From: Jamal Hadi Salim <jhs@...atatu.com>
To: "Gustavo A. R. Silva" <gustavoars@...nel.org>
Cc: Cong Wang <xiyou.wangcong@...il.com>, Jiri Pirko <jiri@...nulli.us>, 
	"David S. Miller" <davem@...emloft.net>, Eric Dumazet <edumazet@...gle.com>, 
	Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>, netdev@...r.kernel.org, 
	linux-kernel@...r.kernel.org, linux-hardening@...r.kernel.org
Subject: Re: [PATCH][next] net: sched: cls_u32: Fix allocation in u32_init()

On Thu, Aug 17, 2023 at 11:57 AM Gustavo A. R. Silva
<gustavoars@...nel.org> wrote:
>
> Replace struct_size() with sizeof(), and avoid allocating 8 too many
> bytes.
>
> The following difference in binary output is expected and reflects the
> desired change:
>
> | net/sched/cls_u32.o
> | @@ -6148,7 +6148,7 @@
> | include/linux/slab.h:599
> |     2cf5:      mov    0x0(%rip),%rdi        # 2cfc <u32_init+0xfc>
> |                        2cf8: R_X86_64_PC32     kmalloc_caches+0xc
> |-    2cfc:      mov    $0x98,%edx
> |+    2cfc:      mov    $0x90,%edx
>
> Fixes: d61491a51f7e ("net/sched: cls_u32: Replace one-element array with flexible-array member")
> Reported-by: Alejandro Colomar <alx@...nel.org>
> Closes: https://lore.kernel.org/lkml/09b4a2ce-da74-3a19-6961-67883f634d98@kernel.org/
> Signed-off-by: Gustavo A. R. Silva <gustavoars@...nel.org>
> ---
>  net/sched/cls_u32.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/net/sched/cls_u32.c b/net/sched/cls_u32.c
> index da4c179a4d41..6663e971a13e 100644
> --- a/net/sched/cls_u32.c
> +++ b/net/sched/cls_u32.c
> @@ -366,7 +366,7 @@ static int u32_init(struct tcf_proto *tp)
>         idr_init(&root_ht->handle_idr);
>
>         if (tp_c == NULL) {
> -               tp_c = kzalloc(struct_size(tp_c, hlist->ht, 1), GFP_KERNEL);
> +               tp_c = kzalloc(sizeof(*tp_c), GFP_KERNEL);
>                 if (tp_c == NULL) {
>                         kfree(root_ht);
>                         return -ENOBUFS;


LGTM.
Acked-by: Jamal Hadi Salim <jhs@...atatu.com>

cheers,
jamal

> 2.34.1
>