[PATCH net v3 resend] net, sunrpc: Remap EPERM in case of connection failure in xs_tcp_setup_socket

[PATCH net v3 resend] net, sunrpc: Remap EPERM in case of connection failure in xs_tcp_setup_socket

[Daniel Borkmann]

When using a BPF program on kernel_connect(), the call can return -EPERM. This
causes xs_tcp_setup_socket() to loop forever, filling up the syslog and causing
the kernel to potentially freeze up.

Neil suggested:

  This will propagate -EPERM up into other layers which might not be ready
  to handle it. It might be safer to map EPERM to an error we would be more
  likely to expect from the network system - such as ECONNREFUSED or ENETDOWN.

ECONNREFUSED as error seems reasonable. For programs setting a different error
can be out of reach (see handling in 4fbac77d2d09) in particular on kernels
which do not have f10d05966196 ("bpf: Make BPF_PROG_RUN_ARRAY return -err
instead of allow boolean"), thus given that it is better to simply remap for
consistent behavior. UDP does handle EPERM in xs_udp_send_request().

Fixes: d74bad4e74ee ("bpf: Hooks for sys_connect")
Fixes: 4fbac77d2d09 ("bpf: Hooks for sys_bind")
Co-developed-by: Lex Siegel <usiegl00@gmail.com>
Signed-off-by: Lex Siegel <usiegl00@gmail.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Cc: Neil Brown <neilb@suse.de>
Cc: Trond Myklebust <trondmy@kernel.org>
Cc: Anna Schumaker <anna@kernel.org>
Link: https://github.com/cilium/cilium/issues/33395
Link: https://lore.kernel.org/bpf/171374175513.12877.8993642908082014881@noble.neil.brown.name
---
 [ Fixes tags are set to the orig connect commit so that stable team
   can pick this up.

   Resend as it turns out that patchwork did not pick up the earlier
   resends likely due to the message id being the same. ]

 v1 -> v2 -> v3:
   - Plain resend, adding correct sunrpc folks to Cc
     https://lore.kernel.org/bpf/Zn7wtStV+iafWRXj@tissot.1015granger.net/

 net/sunrpc/xprtsock.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/net/sunrpc/xprtsock.c b/net/sunrpc/xprtsock.c
index dfc353eea8ed..0e1691316f42 100644
--- a/net/sunrpc/xprtsock.c
+++ b/net/sunrpc/xprtsock.c
@@ -2441,6 +2441,13 @@ static void xs_tcp_setup_socket(struct work_struct *work)
 		transport->srcport = 0;
 		status = -EAGAIN;
 		break;
+	case -EPERM:
+		/* Happens, for instance, if a BPF program is preventing
+		 * the connect. Remap the error so upper layers can better
+		 * deal with it.
+		 */
+		status = -ECONNREFUSED;
+		fallthrough;
 	case -EINVAL:
 		/* Happens, for instance, if the user specified a link
 		 * local IPv6 address without a scope-id.
-- 
2.21.0

Re: [PATCH net v3 resend] net, sunrpc: Remap EPERM in case of connection failure in xs_tcp_setup_socket

[Daniel Borkmann]

On 7/4/24 8:41 AM, Daniel Borkmann wrote:
> When using a BPF program on kernel_connect(), the call can return -EPERM. This
> causes xs_tcp_setup_socket() to loop forever, filling up the syslog and causing
> the kernel to potentially freeze up.
> 
> Neil suggested:
> 
>    This will propagate -EPERM up into other layers which might not be ready
>    to handle it. It might be safer to map EPERM to an error we would be more
>    likely to expect from the network system - such as ECONNREFUSED or ENETDOWN.
> 
> ECONNREFUSED as error seems reasonable. For programs setting a different error
> can be out of reach (see handling in 4fbac77d2d09) in particular on kernels
> which do not have f10d05966196 ("bpf: Make BPF_PROG_RUN_ARRAY return -err
> instead of allow boolean"), thus given that it is better to simply remap for
> consistent behavior. UDP does handle EPERM in xs_udp_send_request().
> 
> Fixes: d74bad4e74ee ("bpf: Hooks for sys_connect")
> Fixes: 4fbac77d2d09 ("bpf: Hooks for sys_bind")
> Co-developed-by: Lex Siegel <usiegl00@gmail.com>
> Signed-off-by: Lex Siegel <usiegl00@gmail.com>
> Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
> Cc: Neil Brown <neilb@suse.de>
> Cc: Trond Myklebust <trondmy@kernel.org>
> Cc: Anna Schumaker <anna@kernel.org>
> Link: https://github.com/cilium/cilium/issues/33395
> Link: https://lore.kernel.org/bpf/171374175513.12877.8993642908082014881@noble.neil.brown.name
> ---
>   [ Fixes tags are set to the orig connect commit so that stable team
>     can pick this up.
> 
>     Resend as it turns out that patchwork did not pick up the earlier
>     resends likely due to the message id being the same. ]
> 
>   v1 -> v2 -> v3:
>     - Plain resend, adding correct sunrpc folks to Cc
>       https://lore.kernel.org/bpf/Zn7wtStV+iafWRXj@tissot.1015granger.net/

(gentle ping)

Re: [PATCH net v3 resend] net, sunrpc: Remap EPERM in case of connection failure in xs_tcp_setup_socket

[Paolo Abeni]

On Thu, 2024-07-04 at 08:41 +0200, Daniel Borkmann wrote:
> When using a BPF program on kernel_connect(), the call can return -EPERM. This
> causes xs_tcp_setup_socket() to loop forever, filling up the syslog and causing
> the kernel to potentially freeze up.
> 
> Neil suggested:
> 
>   This will propagate -EPERM up into other layers which might not be ready
>   to handle it. It might be safer to map EPERM to an error we would be more
>   likely to expect from the network system - such as ECONNREFUSED or ENETDOWN.
> 
> ECONNREFUSED as error seems reasonable. For programs setting a different error
> can be out of reach (see handling in 4fbac77d2d09) in particular on kernels
> which do not have f10d05966196 ("bpf: Make BPF_PROG_RUN_ARRAY return -err
> instead of allow boolean"), thus given that it is better to simply remap for
> consistent behavior. UDP does handle EPERM in xs_udp_send_request().
> 
> Fixes: d74bad4e74ee ("bpf: Hooks for sys_connect")
> Fixes: 4fbac77d2d09 ("bpf: Hooks for sys_bind")
> Co-developed-by: Lex Siegel <usiegl00@gmail.com>
> Signed-off-by: Lex Siegel <usiegl00@gmail.com>
> Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
> Cc: Neil Brown <neilb@suse.de>
> Cc: Trond Myklebust <trondmy@kernel.org>
> Cc: Anna Schumaker <anna@kernel.org>
> Link: https://github.com/cilium/cilium/issues/33395
> Link: https://lore.kernel.org/bpf/171374175513.12877.8993642908082014881@noble.neil.brown.name
> ---
>  [ Fixes tags are set to the orig connect commit so that stable team
>    can pick this up.
> 
>    Resend as it turns out that patchwork did not pick up the earlier
>    resends likely due to the message id being the same. ]
> 
>  v1 -> v2 -> v3:
>    - Plain resend, adding correct sunrpc folks to Cc
>      https://lore.kernel.org/bpf/Zn7wtStV+iafWRXj@tissot.1015granger.net/
> 
>  net/sunrpc/xprtsock.c | 7 +++++++
>  1 file changed, 7 insertions(+)
> 
> diff --git a/net/sunrpc/xprtsock.c b/net/sunrpc/xprtsock.c
> index dfc353eea8ed..0e1691316f42 100644
> --- a/net/sunrpc/xprtsock.c
> +++ b/net/sunrpc/xprtsock.c
> @@ -2441,6 +2441,13 @@ static void xs_tcp_setup_socket(struct work_struct *work)
>  		transport->srcport = 0;
>  		status = -EAGAIN;
>  		break;
> +	case -EPERM:
> +		/* Happens, for instance, if a BPF program is preventing
> +		 * the connect. Remap the error so upper layers can better
> +		 * deal with it.
> +		 */
> +		status = -ECONNREFUSED;
> +		fallthrough;
>  	case -EINVAL:
>  		/* Happens, for instance, if the user specified a link
>  		 * local IPv6 address without a scope-id.

The patch looks sane to me. @Trond, @Anna, are you ok for this to go
directly into the net tree?

Thanks!

Paolo

Re: [PATCH net v3 resend] net, sunrpc: Remap EPERM in case of connection failure in xs_tcp_setup_socket

[Paolo Abeni]

On Tue, 2024-07-09 at 10:22 +0200, Paolo Abeni wrote:
> On Thu, 2024-07-04 at 08:41 +0200, Daniel Borkmann wrote:
> > When using a BPF program on kernel_connect(), the call can return -EPERM. This
> > causes xs_tcp_setup_socket() to loop forever, filling up the syslog and causing
> > the kernel to potentially freeze up.
> > 
> > Neil suggested:
> > 
> >   This will propagate -EPERM up into other layers which might not be ready
> >   to handle it. It might be safer to map EPERM to an error we would be more
> >   likely to expect from the network system - such as ECONNREFUSED or ENETDOWN.
> > 
> > ECONNREFUSED as error seems reasonable. For programs setting a different error
> > can be out of reach (see handling in 4fbac77d2d09) in particular on kernels
> > which do not have f10d05966196 ("bpf: Make BPF_PROG_RUN_ARRAY return -err
> > instead of allow boolean"), thus given that it is better to simply remap for
> > consistent behavior. UDP does handle EPERM in xs_udp_send_request().
> > 
> > Fixes: d74bad4e74ee ("bpf: Hooks for sys_connect")
> > Fixes: 4fbac77d2d09 ("bpf: Hooks for sys_bind")
> > Co-developed-by: Lex Siegel <usiegl00@gmail.com>
> > Signed-off-by: Lex Siegel <usiegl00@gmail.com>
> > Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
> > Cc: Neil Brown <neilb@suse.de>
> > Cc: Trond Myklebust <trondmy@kernel.org>
> > Cc: Anna Schumaker <anna@kernel.org>
> > Link: https://github.com/cilium/cilium/issues/33395
> > Link: https://lore.kernel.org/bpf/171374175513.12877.8993642908082014881@noble.neil.brown.name
> > ---
> >  [ Fixes tags are set to the orig connect commit so that stable team
> >    can pick this up.
> > 
> >    Resend as it turns out that patchwork did not pick up the earlier
> >    resends likely due to the message id being the same. ]
> > 
> >  v1 -> v2 -> v3:
> >    - Plain resend, adding correct sunrpc folks to Cc
> >      https://lore.kernel.org/bpf/Zn7wtStV+iafWRXj@tissot.1015granger.net/
> > 
> >  net/sunrpc/xprtsock.c | 7 +++++++
> >  1 file changed, 7 insertions(+)
> > 
> > diff --git a/net/sunrpc/xprtsock.c b/net/sunrpc/xprtsock.c
> > index dfc353eea8ed..0e1691316f42 100644
> > --- a/net/sunrpc/xprtsock.c
> > +++ b/net/sunrpc/xprtsock.c
> > @@ -2441,6 +2441,13 @@ static void xs_tcp_setup_socket(struct work_struct *work)
> >  		transport->srcport = 0;
> >  		status = -EAGAIN;
> >  		break;
> > +	case -EPERM:
> > +		/* Happens, for instance, if a BPF program is preventing
> > +		 * the connect. Remap the error so upper layers can better
> > +		 * deal with it.
> > +		 */
> > +		status = -ECONNREFUSED;
> > +		fallthrough;
> >  	case -EINVAL:
> >  		/* Happens, for instance, if the user specified a link
> >  		 * local IPv6 address without a scope-id.
> 
> The patch looks sane to me. @Trond, @Anna, are you ok for this to go
> directly into the net tree?

FTR, I think it's better to have it in today's net PR, so unless
someone scream very loudly very soon, I'm going to merge it.

Thanks,

Paolo

Re: [PATCH net v3 resend] net, sunrpc: Remap EPERM in case of connection failure in xs_tcp_setup_socket

[patchwork-bot+netdevbpf]

Hello:

This patch was applied to netdev/net.git (main)
by Paolo Abeni <pabeni@redhat.com>:

On Thu,  4 Jul 2024 08:41:57 +0200 you wrote:
> When using a BPF program on kernel_connect(), the call can return -EPERM. This
> causes xs_tcp_setup_socket() to loop forever, filling up the syslog and causing
> the kernel to potentially freeze up.
> 
> Neil suggested:
> 
>   This will propagate -EPERM up into other layers which might not be ready
>   to handle it. It might be safer to map EPERM to an error we would be more
>   likely to expect from the network system - such as ECONNREFUSED or ENETDOWN.
> 
> [...]

Here is the summary with links:
  - [net,v3,resend] net, sunrpc: Remap EPERM in case of connection failure in xs_tcp_setup_socket
    https://git.kernel.org/netdev/net/c/626dfed5fa3b

You are awesome, thank you!
-- 
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