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Date: Sun, 13 Dec 2020 11:48:15 +0200 From: Yonatan Linik <yonatanlinik@...il.com> To: Jakub Kicinski <kuba@...nel.org> Cc: David Miller <davem@...emloft.net>, Alexei Starovoitov <ast@...nel.org>, Daniel Borkmann <daniel@...earbox.net>, Martin KaFai Lau <kafai@...com>, Song Liu <songliubraving@...com>, Yonghong Song <yhs@...com>, Andrii Nakryiko <andriin@...com>, John Fastabend <john.fastabend@...il.com>, KP Singh <kpsingh@...omium.org>, Willem de Bruijn <willemb@...gle.com>, john.ogness@...utronix.de, Arnd Bergmann <arnd@...db.de>, Mao Wenan <maowenan@...wei.com>, Colin Ian King <colin.king@...onical.com>, orcohen@...oaltonetworks.com, Networking <netdev@...r.kernel.org>, linux-kernel@...r.kernel.org, bpf <bpf@...r.kernel.org> Subject: Re: [PATCH 1/1] net: Fix use of proc_fs On Sat, Dec 12, 2020 at 11:51 PM Jakub Kicinski <kuba@...nel.org> wrote: > > On Sat, 12 Dec 2020 23:39:20 +0200 Yonatan Linik wrote: > > On Sat, Dec 12, 2020 at 9:48 PM Jakub Kicinski <kuba@...nel.org> wrote: > > > > > > On Fri, 11 Dec 2020 18:37:49 +0200 Yonatan Linik wrote: > > > > proc_fs was used, in af_packet, without a surrounding #ifdef, > > > > although there is no hard dependency on proc_fs. > > > > That caused the initialization of the af_packet module to fail > > > > when CONFIG_PROC_FS=n. > > > > > > > > Specifically, proc_create_net() was used in af_packet.c, > > > > and when it fails, packet_net_init() returns -ENOMEM. > > > > It will always fail when the kernel is compiled without proc_fs, > > > > because, proc_create_net() for example always returns NULL. > > > > > > > > The calling order that starts in af_packet.c is as follows: > > > > packet_init() > > > > register_pernet_subsys() > > > > register_pernet_operations() > > > > __register_pernet_operations() > > > > ops_init() > > > > ops->init() (packet_net_ops.init=packet_net_init()) > > > > proc_create_net() > > > > > > > > It worked in the past because register_pernet_subsys()'s return value > > > > wasn't checked before this Commit 36096f2f4fa0 ("packet: Fix error path in > > > > packet_init."). > > > > It always returned an error, but was not checked before, so everything > > > > was working even when CONFIG_PROC_FS=n. > > > > > > > > The fix here is simply to add the necessary #ifdef. > > > > > > > > Signed-off-by: Yonatan Linik <yonatanlinik@...il.com> > > > > > > Hm, I'm guessing you hit this on a kernel upgrade of a real system? > > > > Yeah, suddenly using socket with AF_PACKET didn't work, > > so I checked what happened. > > > > > It seems like all callers to proc_create_net (and friends) interpret > > > NULL as an error, but only handful is protected by an ifdef. > > > > I guess where there is no ifdef, > > there should be a hard dependency on procfs, > > using depends on in the Kconfig. > > Maybe that's not the case everywhere it should be. > > You're right, on a closer look most of the places have a larger #ifdef > block (which my grep didn't catch) or are under Kconfig. Of those I > checked only TLS looks wrong (good job me) - would you care to fix that > one as well, or should I? I can fix that as well, you are talking about tls_proc.c, right?
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