[PATCH 8/9] bpf: Check address length before reading address family

[PATCH 8/9] bpf: Check address length before reading address family

[Tetsuo Handa]

KMSAN will complain if valid address length passed to bpf_bind() is
shorter than sizeof("struct sockaddr"->sa_family) bytes.

Signed-off-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
---
 net/core/filter.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/net/core/filter.c b/net/core/filter.c
index 41f633cf4fc1..b9089fda4367 100644
--- a/net/core/filter.c
+++ b/net/core/filter.c
@@ -4458,6 +4458,8 @@ BPF_CALL_3(bpf_bind, struct bpf_sock_addr_kern *, ctx, struct sockaddr *, addr,
 	 * Only binding to IP is supported.
 	 */
 	err = -EINVAL;
+	if (addr_len < offsetofend(struct sockaddr, sa_family))
+		return err;
 	if (addr->sa_family == AF_INET) {
 		if (addr_len < sizeof(struct sockaddr_in))
 			return err;
-- 
2.16.5

Re: [PATCH 8/9] bpf: Check address length before reading address family

[Alexei Starovoitov]

On Fri, Apr 12, 2019 at 3:56 AM Tetsuo Handa
<penguin-kernel@i-love.sakura.ne.jp> wrote:
>
> KMSAN will complain if valid address length passed to bpf_bind() is
> shorter than sizeof("struct sockaddr"->sa_family) bytes.
>
> Signed-off-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
> ---
>  net/core/filter.c | 2 ++
>  1 file changed, 2 insertions(+)
>
> diff --git a/net/core/filter.c b/net/core/filter.c
> index 41f633cf4fc1..b9089fda4367 100644
> --- a/net/core/filter.c
> +++ b/net/core/filter.c
> @@ -4458,6 +4458,8 @@ BPF_CALL_3(bpf_bind, struct bpf_sock_addr_kern *, ctx, struct sockaddr *, addr,
>          * Only binding to IP is supported.
>          */
>         err = -EINVAL;
> +       if (addr_len < offsetofend(struct sockaddr, sa_family))
> +               return err;

the verifier will check that addr_len is not zero,
but it can be one byte, so it's a good check.
Thanks!

>         if (addr->sa_family == AF_INET) {
>                 if (addr_len < sizeof(struct sockaddr_in))
>                         return err;
> --
> 2.16.5
>

Re: [PATCH 8/9] bpf: Check address length before reading address family

[Andrey Ignatov]

Alexei Starovoitov <alexei.starovoitov@gmail.com> [Fri, 2019-04-12 09:20 -0700]:
> On Fri, Apr 12, 2019 at 3:56 AM Tetsuo Handa
> <penguin-kernel@i-love.sakura.ne.jp> wrote:
> >
> > KMSAN will complain if valid address length passed to bpf_bind() is
> > shorter than sizeof("struct sockaddr"->sa_family) bytes.
> >
> > Signed-off-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
> > ---
> >  net/core/filter.c | 2 ++
> >  1 file changed, 2 insertions(+)
> >
> > diff --git a/net/core/filter.c b/net/core/filter.c
> > index 41f633cf4fc1..b9089fda4367 100644
> > --- a/net/core/filter.c
> > +++ b/net/core/filter.c
> > @@ -4458,6 +4458,8 @@ BPF_CALL_3(bpf_bind, struct bpf_sock_addr_kern *, ctx, struct sockaddr *, addr,
> >          * Only binding to IP is supported.
> >          */
> >         err = -EINVAL;
> > +       if (addr_len < offsetofend(struct sockaddr, sa_family))
> > +               return err;
> 
> the verifier will check that addr_len is not zero,
> but it can be one byte, so it's a good check.
> Thanks!

True, I missed this corner-case. Thanks for fixing.

Acked-by: Andrey Ignatov <rdna@fb.com>


> >         if (addr->sa_family == AF_INET) {
> >                 if (addr_len < sizeof(struct sockaddr_in))
> >                         return err;
> > --
> > 2.16.5
> >

-- 
Andrey Ignatov

Re: [PATCH 8/9] bpf: Check address length before reading address family

[David Miller]

From: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Date: Fri, 12 Apr 2019 19:55:47 +0900

> KMSAN will complain if valid address length passed to bpf_bind() is
> shorter than sizeof("struct sockaddr"->sa_family) bytes.
> 
> Signed-off-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>

Applied.