| Message ID | tencent_284407955020261D1B2BD142194A87C9EB0A@qq.com (mailing list archive) |
|---|---|
| State | Awaiting Upstream |
| Delegated to: | Netdev Maintainers |
| Headers | show |
| Series | netfilter: mark racy access on ext->gen_id | expand |
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.
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?
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.
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;
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.
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;
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(-)