* [PATCH] netfilter: mark racy access on ext->gen_id
@ 2024-04-23 11:50 linke li
2024-04-23 12:03 ` Florian Westphal
2024-04-25 9:36 ` Pablo Neira Ayuso
0 siblings, 2 replies; 6+ messages in thread
From: linke li @ 2024-04-23 11:50 UTC (permalink / raw)
Cc: xujianhao01, linke li, Pablo Neira Ayuso, Jozsef Kadlecsik,
Florian Westphal, David S. Miller, Eric Dumazet, Jakub Kicinski,
Paolo Abeni, netfilter-devel, coreteam, netdev, linux-kernel
In __nf_ct_ext_find(), ext->gen_id can be changed by
nf_ct_ext_valid_post(), using WRITE_ONCE. Mark data races on ext->gen_id
as benign using READ_ONCE.
This patch is aimed at reducing the number of benign races reported by
KCSAN in order to focus future debugging effort on harmful races.
Signed-off-by: linke li <lilinke99@qq.com>
---
net/netfilter/nf_conntrack_extend.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/net/netfilter/nf_conntrack_extend.c b/net/netfilter/nf_conntrack_extend.c
index dd62cc12e775..7f1a5e5f6646 100644
--- a/net/netfilter/nf_conntrack_extend.c
+++ b/net/netfilter/nf_conntrack_extend.c
@@ -141,7 +141,7 @@ void *__nf_ct_ext_find(const struct nf_ct_ext *ext, u8 id)
if (!__nf_ct_ext_exist(ext, id))
return NULL;
- if (this_id == 0 || ext->gen_id == gen_id)
+ if (this_id == 0 || READ_ONCE(ext->gen_id) == gen_id)
return (void *)ext + ext->offset[id];
return NULL;
--
2.39.3 (Apple Git-146)
^ permalink raw reply related [flat|nested] 6+ messages in thread
* Re: [PATCH] netfilter: mark racy access on ext->gen_id
2024-04-23 11:50 [PATCH] netfilter: mark racy access on ext->gen_id linke li
@ 2024-04-23 12:03 ` Florian Westphal
2024-04-24 22:20 ` Pablo Neira Ayuso
2024-04-25 9:36 ` Pablo Neira Ayuso
1 sibling, 1 reply; 6+ messages in thread
From: Florian Westphal @ 2024-04-23 12:03 UTC (permalink / raw)
To: linke li
Cc: xujianhao01, Pablo Neira Ayuso, Jozsef Kadlecsik,
Florian Westphal, David S. Miller, Eric Dumazet, Jakub Kicinski,
Paolo Abeni, netfilter-devel, coreteam, netdev, linux-kernel
linke li <lilinke99@qq.com> wrote:
> In __nf_ct_ext_find(), ext->gen_id can be changed by
> nf_ct_ext_valid_post(), using WRITE_ONCE. Mark data races on ext->gen_id
> as benign using READ_ONCE.
>
> This patch is aimed at reducing the number of benign races reported by
> KCSAN in order to focus future debugging effort on harmful races.
Acked-by: Florian Westphal <fw@strlen.de>
Should proably go to nf tree.
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH] netfilter: mark racy access on ext->gen_id
2024-04-23 12:03 ` Florian Westphal
@ 2024-04-24 22:20 ` Pablo Neira Ayuso
0 siblings, 0 replies; 6+ messages in thread
From: Pablo Neira Ayuso @ 2024-04-24 22:20 UTC (permalink / raw)
To: Florian Westphal
Cc: linke li, xujianhao01, Jozsef Kadlecsik, David S. Miller,
Eric Dumazet, Jakub Kicinski, Paolo Abeni, netfilter-devel,
coreteam, netdev, linux-kernel
On Tue, Apr 23, 2024 at 02:03:09PM +0200, Florian Westphal wrote:
> linke li <lilinke99@qq.com> wrote:
> > In __nf_ct_ext_find(), ext->gen_id can be changed by
> > nf_ct_ext_valid_post(), using WRITE_ONCE. Mark data races on ext->gen_id
> > as benign using READ_ONCE.
> >
> > This patch is aimed at reducing the number of benign races reported by
> > KCSAN in order to focus future debugging effort on harmful races.
>
> Acked-by: Florian Westphal <fw@strlen.de>
>
> Should proably go to nf tree.
Can I get a Fixes: tag for this one?
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH] netfilter: mark racy access on ext->gen_id
2024-04-23 11:50 [PATCH] netfilter: mark racy access on ext->gen_id linke li
2024-04-23 12:03 ` Florian Westphal
@ 2024-04-25 9:36 ` Pablo Neira Ayuso
2024-04-25 9:54 ` Eric Dumazet
1 sibling, 1 reply; 6+ messages in thread
From: Pablo Neira Ayuso @ 2024-04-25 9:36 UTC (permalink / raw)
To: linke li
Cc: xujianhao01, Jozsef Kadlecsik, Florian Westphal, David S. Miller,
Eric Dumazet, Jakub Kicinski, Paolo Abeni, netfilter-devel,
coreteam, netdev, linux-kernel
On Tue, Apr 23, 2024 at 07:50:22PM +0800, linke li wrote:
> In __nf_ct_ext_find(), ext->gen_id can be changed by
> nf_ct_ext_valid_post(), using WRITE_ONCE. Mark data races on ext->gen_id
> as benign using READ_ONCE.
>
> This patch is aimed at reducing the number of benign races reported by
> KCSAN in order to focus future debugging effort on harmful races.
There are a more uses ext->gen_id in the code, my understanding this
patch is just a stub.
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH] netfilter: mark racy access on ext->gen_id
2024-04-25 9:36 ` Pablo Neira Ayuso
@ 2024-04-25 9:54 ` Eric Dumazet
2024-04-25 10:04 ` Florian Westphal
0 siblings, 1 reply; 6+ messages in thread
From: Eric Dumazet @ 2024-04-25 9:54 UTC (permalink / raw)
To: Pablo Neira Ayuso
Cc: linke li, xujianhao01, Jozsef Kadlecsik, Florian Westphal,
David S. Miller, Jakub Kicinski, Paolo Abeni, netfilter-devel,
coreteam, netdev, linux-kernel
On Thu, Apr 25, 2024 at 11:36 AM Pablo Neira Ayuso <pablo@netfilter.org> wrote:
>
> On Tue, Apr 23, 2024 at 07:50:22PM +0800, linke li wrote:
> > In __nf_ct_ext_find(), ext->gen_id can be changed by
> > nf_ct_ext_valid_post(), using WRITE_ONCE. Mark data races on ext->gen_id
> > as benign using READ_ONCE.
> >
> > This patch is aimed at reducing the number of benign races reported by
> > KCSAN in order to focus future debugging effort on harmful races.
>
> There are a more uses ext->gen_id in the code, my understanding this
> patch is just a stub.
Anyway, ext->gen_id was already read and stored in @this_id
I would probably avoid reading it a second time.
diff --git a/net/netfilter/nf_conntrack_extend.c
b/net/netfilter/nf_conntrack_extend.c
index dd62cc12e7750734fec9be8a90fd0defcbc815e0..747797b20bc7417a2b7270d84f62d24991a4b982
100644
--- a/net/netfilter/nf_conntrack_extend.c
+++ b/net/netfilter/nf_conntrack_extend.c
@@ -141,7 +141,7 @@ void *__nf_ct_ext_find(const struct nf_ct_ext *ext, u8 id)
if (!__nf_ct_ext_exist(ext, id))
return NULL;
- if (this_id == 0 || ext->gen_id == gen_id)
+ if (this_id == 0 || this_id == gen_id)
return (void *)ext + ext->offset[id];
return NULL;
^ permalink raw reply [flat|nested] 6+ messages in thread* Re: [PATCH] netfilter: mark racy access on ext->gen_id
2024-04-25 9:54 ` Eric Dumazet
@ 2024-04-25 10:04 ` Florian Westphal
0 siblings, 0 replies; 6+ messages in thread
From: Florian Westphal @ 2024-04-25 10:04 UTC (permalink / raw)
To: Eric Dumazet
Cc: Pablo Neira Ayuso, linke li, xujianhao01, Jozsef Kadlecsik,
Florian Westphal, David S. Miller, Jakub Kicinski, Paolo Abeni,
netfilter-devel, coreteam, netdev, linux-kernel
Eric Dumazet <edumazet@google.com> wrote:
> > There are a more uses ext->gen_id in the code, my understanding this
> > patch is just a stub.
>
> Anyway, ext->gen_id was already read and stored in @this_id
>
> I would probably avoid reading it a second time.
> diff --git a/net/netfilter/nf_conntrack_extend.c
> b/net/netfilter/nf_conntrack_extend.c
> index dd62cc12e7750734fec9be8a90fd0defcbc815e0..747797b20bc7417a2b7270d84f62d24991a4b982
> 100644
> --- a/net/netfilter/nf_conntrack_extend.c
> +++ b/net/netfilter/nf_conntrack_extend.c
> @@ -141,7 +141,7 @@ void *__nf_ct_ext_find(const struct nf_ct_ext *ext, u8 id)
> if (!__nf_ct_ext_exist(ext, id))
> return NULL;
>
> - if (this_id == 0 || ext->gen_id == gen_id)
> + if (this_id == 0 || this_id == gen_id)
> return (void *)ext + ext->offset[id];
>
> return NULL;
>
Right, that should work, unconfirmed entries are not exposed to other
cpus and confirmed entries get their id set to 0.
^ permalink raw reply [flat|nested] 6+ messages in thread
end of thread, other threads:[~2024-04-25 10:04 UTC | newest]
Thread overview: 6+ messages (download: mbox.gz follow: Atom feed
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2024-04-23 11:50 [PATCH] netfilter: mark racy access on ext->gen_id linke li
2024-04-23 12:03 ` Florian Westphal
2024-04-24 22:20 ` Pablo Neira Ayuso
2024-04-25 9:36 ` Pablo Neira Ayuso
2024-04-25 9:54 ` Eric Dumazet
2024-04-25 10:04 ` Florian Westphal
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