diff mbox series

[bpf-next,v2,01/28] bpf: add new is_sys_admin_prog_type() helper

Message ID 20220304172852.274126-2-benjamin.tissoires@redhat.com (mailing list archive)
State New
Headers show
Series Introduce eBPF support for HID devices | expand

Commit Message

Benjamin Tissoires March 4, 2022, 5:28 p.m. UTC
LIRC_MODE2 does not really need net_admin capability, but only sys_admin.

Extract a new helper for it, it will be also used for the HID bpf
implementation.

Cc: Sean Young <sean@mess.org>
Signed-off-by: Benjamin Tissoires <benjamin.tissoires@redhat.com>

---

new in v2
---
 kernel/bpf/syscall.c | 14 +++++++++++++-
 1 file changed, 13 insertions(+), 1 deletion(-)

Comments

Song Liu March 4, 2022, 11:12 p.m. UTC | #1
On Fri, Mar 4, 2022 at 9:30 AM Benjamin Tissoires
<benjamin.tissoires@redhat.com> wrote:
>
> LIRC_MODE2 does not really need net_admin capability, but only sys_admin.
>
> Extract a new helper for it, it will be also used for the HID bpf
> implementation.
>
> Cc: Sean Young <sean@mess.org>
> Signed-off-by: Benjamin Tissoires <benjamin.tissoires@redhat.com>
>
> ---
>
> new in v2
> ---
>  kernel/bpf/syscall.c | 14 +++++++++++++-
>  1 file changed, 13 insertions(+), 1 deletion(-)
>
> diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
> index db402ebc5570..cc570891322b 100644
> --- a/kernel/bpf/syscall.c
> +++ b/kernel/bpf/syscall.c
> @@ -2165,7 +2165,6 @@ static bool is_net_admin_prog_type(enum bpf_prog_type prog_type)
>         case BPF_PROG_TYPE_LWT_SEG6LOCAL:
>         case BPF_PROG_TYPE_SK_SKB:
>         case BPF_PROG_TYPE_SK_MSG:
> -       case BPF_PROG_TYPE_LIRC_MODE2:
>         case BPF_PROG_TYPE_FLOW_DISSECTOR:
>         case BPF_PROG_TYPE_CGROUP_DEVICE:
>         case BPF_PROG_TYPE_CGROUP_SOCK:
> @@ -2202,6 +2201,17 @@ static bool is_perfmon_prog_type(enum bpf_prog_type prog_type)
>         }
>  }
>
> +static bool is_sys_admin_prog_type(enum bpf_prog_type prog_type)
> +{
> +       switch (prog_type) {
> +       case BPF_PROG_TYPE_LIRC_MODE2:
> +       case BPF_PROG_TYPE_EXT: /* extends any prog */
> +               return true;
> +       default:
> +               return false;
> +       }
> +}

I am not sure whether we should do this. This is a behavior change, that may
break some user space. Also, BPF_PROG_TYPE_EXT is checked in
is_perfmon_prog_type(), and this change will make that case useless.

Thanks,
Song

[...]
Benjamin Tissoires March 5, 2022, 10:07 a.m. UTC | #2
On Sat, Mar 5, 2022 at 12:12 AM Song Liu <song@kernel.org> wrote:
>
> On Fri, Mar 4, 2022 at 9:30 AM Benjamin Tissoires
> <benjamin.tissoires@redhat.com> wrote:
> >
> > LIRC_MODE2 does not really need net_admin capability, but only sys_admin.
> >
> > Extract a new helper for it, it will be also used for the HID bpf
> > implementation.
> >
> > Cc: Sean Young <sean@mess.org>
> > Signed-off-by: Benjamin Tissoires <benjamin.tissoires@redhat.com>
> >
> > ---
> >
> > new in v2
> > ---
> >  kernel/bpf/syscall.c | 14 +++++++++++++-
> >  1 file changed, 13 insertions(+), 1 deletion(-)
> >
> > diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
> > index db402ebc5570..cc570891322b 100644
> > --- a/kernel/bpf/syscall.c
> > +++ b/kernel/bpf/syscall.c
> > @@ -2165,7 +2165,6 @@ static bool is_net_admin_prog_type(enum bpf_prog_type prog_type)
> >         case BPF_PROG_TYPE_LWT_SEG6LOCAL:
> >         case BPF_PROG_TYPE_SK_SKB:
> >         case BPF_PROG_TYPE_SK_MSG:
> > -       case BPF_PROG_TYPE_LIRC_MODE2:
> >         case BPF_PROG_TYPE_FLOW_DISSECTOR:
> >         case BPF_PROG_TYPE_CGROUP_DEVICE:
> >         case BPF_PROG_TYPE_CGROUP_SOCK:
> > @@ -2202,6 +2201,17 @@ static bool is_perfmon_prog_type(enum bpf_prog_type prog_type)
> >         }
> >  }
> >
> > +static bool is_sys_admin_prog_type(enum bpf_prog_type prog_type)
> > +{
> > +       switch (prog_type) {
> > +       case BPF_PROG_TYPE_LIRC_MODE2:
> > +       case BPF_PROG_TYPE_EXT: /* extends any prog */
> > +               return true;
> > +       default:
> > +               return false;
> > +       }
> > +}
>
> I am not sure whether we should do this. This is a behavior change, that may
> break some user space. Also, BPF_PROG_TYPE_EXT is checked in
> is_perfmon_prog_type(), and this change will make that case useless.

Sure, I can drop it from v3 and make this function appear for HID only.

Regarding BPF_PROG_TYPE_EXT, it was already in both
is_net_admin_prog_type() and is_perfmon_prog_type(), so I duplicated
it here, but I agree, given that it's already in the first function
there, CPA_SYS_ADMIN is already checked.

Cheers,
Benjamin

>
> Thanks,
> Song
>
> [...]
>
Sean Young March 5, 2022, 4:58 p.m. UTC | #3
On Sat, Mar 05, 2022 at 11:07:04AM +0100, Benjamin Tissoires wrote:
> On Sat, Mar 5, 2022 at 12:12 AM Song Liu <song@kernel.org> wrote:
> >
> > On Fri, Mar 4, 2022 at 9:30 AM Benjamin Tissoires
> > <benjamin.tissoires@redhat.com> wrote:
> > >
> > > LIRC_MODE2 does not really need net_admin capability, but only sys_admin.
> > >
> > > Extract a new helper for it, it will be also used for the HID bpf
> > > implementation.
> > >
> > > Cc: Sean Young <sean@mess.org>
> > > Signed-off-by: Benjamin Tissoires <benjamin.tissoires@redhat.com>
> > >
> > > ---
> > >
> > > new in v2
> > > ---
> > >  kernel/bpf/syscall.c | 14 +++++++++++++-
> > >  1 file changed, 13 insertions(+), 1 deletion(-)
> > >
> > > diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
> > > index db402ebc5570..cc570891322b 100644
> > > --- a/kernel/bpf/syscall.c
> > > +++ b/kernel/bpf/syscall.c
> > > @@ -2165,7 +2165,6 @@ static bool is_net_admin_prog_type(enum bpf_prog_type prog_type)
> > >         case BPF_PROG_TYPE_LWT_SEG6LOCAL:
> > >         case BPF_PROG_TYPE_SK_SKB:
> > >         case BPF_PROG_TYPE_SK_MSG:
> > > -       case BPF_PROG_TYPE_LIRC_MODE2:
> > >         case BPF_PROG_TYPE_FLOW_DISSECTOR:
> > >         case BPF_PROG_TYPE_CGROUP_DEVICE:
> > >         case BPF_PROG_TYPE_CGROUP_SOCK:
> > > @@ -2202,6 +2201,17 @@ static bool is_perfmon_prog_type(enum bpf_prog_type prog_type)
> > >         }
> > >  }
> > >
> > > +static bool is_sys_admin_prog_type(enum bpf_prog_type prog_type)
> > > +{
> > > +       switch (prog_type) {
> > > +       case BPF_PROG_TYPE_LIRC_MODE2:
> > > +       case BPF_PROG_TYPE_EXT: /* extends any prog */
> > > +               return true;
> > > +       default:
> > > +               return false;
> > > +       }
> > > +}
> >
> > I am not sure whether we should do this. This is a behavior change, that may
> > break some user space. Also, BPF_PROG_TYPE_EXT is checked in
> > is_perfmon_prog_type(), and this change will make that case useless.
> 
> Sure, I can drop it from v3 and make this function appear for HID only.

For BPF_PROG_TYPE_LIRC_MODE2, I don't think this change will break userspace.
This is called from ir-keytable(1) which is called from udev. It should have
all the necessary permissions.

In addition, the vast majority IR decoders are non-bpf. bpf ir decoders have
very few users at the moment.

I am working on completely new userspace tooling which will make extensive
use of bpf ir decoding with full lircd and IRP compatibility, but this is not
finished yet (see https://github.com/seanyoung/cir).

Thanks

Sean
Song Liu March 7, 2022, 6:23 p.m. UTC | #4
On Sat, Mar 5, 2022 at 2:07 AM Benjamin Tissoires
<benjamin.tissoires@redhat.com> wrote:
>
> On Sat, Mar 5, 2022 at 12:12 AM Song Liu <song@kernel.org> wrote:
> >
> > On Fri, Mar 4, 2022 at 9:30 AM Benjamin Tissoires
> > <benjamin.tissoires@redhat.com> wrote:
> > >
> > > LIRC_MODE2 does not really need net_admin capability, but only sys_admin.
> > >
> > > Extract a new helper for it, it will be also used for the HID bpf
> > > implementation.
> > >
> > > Cc: Sean Young <sean@mess.org>
> > > Signed-off-by: Benjamin Tissoires <benjamin.tissoires@redhat.com>
> > >
> > > ---
> > >
> > > new in v2
> > > ---
> > >  kernel/bpf/syscall.c | 14 +++++++++++++-
> > >  1 file changed, 13 insertions(+), 1 deletion(-)
> > >
> > > diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
> > > index db402ebc5570..cc570891322b 100644
> > > --- a/kernel/bpf/syscall.c
> > > +++ b/kernel/bpf/syscall.c
> > > @@ -2165,7 +2165,6 @@ static bool is_net_admin_prog_type(enum bpf_prog_type prog_type)
> > >         case BPF_PROG_TYPE_LWT_SEG6LOCAL:
> > >         case BPF_PROG_TYPE_SK_SKB:
> > >         case BPF_PROG_TYPE_SK_MSG:
> > > -       case BPF_PROG_TYPE_LIRC_MODE2:
> > >         case BPF_PROG_TYPE_FLOW_DISSECTOR:
> > >         case BPF_PROG_TYPE_CGROUP_DEVICE:
> > >         case BPF_PROG_TYPE_CGROUP_SOCK:
> > > @@ -2202,6 +2201,17 @@ static bool is_perfmon_prog_type(enum bpf_prog_type prog_type)
> > >         }
> > >  }
> > >
> > > +static bool is_sys_admin_prog_type(enum bpf_prog_type prog_type)
> > > +{
> > > +       switch (prog_type) {
> > > +       case BPF_PROG_TYPE_LIRC_MODE2:
> > > +       case BPF_PROG_TYPE_EXT: /* extends any prog */
> > > +               return true;
> > > +       default:
> > > +               return false;
> > > +       }
> > > +}
> >
> > I am not sure whether we should do this. This is a behavior change, that may
> > break some user space. Also, BPF_PROG_TYPE_EXT is checked in
> > is_perfmon_prog_type(), and this change will make that case useless.
>
> Sure, I can drop it from v3 and make this function appear for HID only.
>
> Regarding BPF_PROG_TYPE_EXT, it was already in both
> is_net_admin_prog_type() and is_perfmon_prog_type(), so I duplicated
> it here, but I agree, given that it's already in the first function
> there, CPA_SYS_ADMIN is already checked.

I think with current code, a user with CAP_BPF, CAP_NET_ADMIN, and
CAP_PERFMON (but not CAP_SYS_ADMIN) can load programs of type
BPF_PROG_TYPE_EXT. But after the patch, the same user will not be
able to do it. Did I misread it? It is not a common case though.
Song Liu March 7, 2022, 6:26 p.m. UTC | #5
On Sat, Mar 5, 2022 at 8:58 AM Sean Young <sean@mess.org> wrote:
>
> On Sat, Mar 05, 2022 at 11:07:04AM +0100, Benjamin Tissoires wrote:
> > On Sat, Mar 5, 2022 at 12:12 AM Song Liu <song@kernel.org> wrote:
> > >
> > > On Fri, Mar 4, 2022 at 9:30 AM Benjamin Tissoires
> > > <benjamin.tissoires@redhat.com> wrote:
> > > >
> > > > LIRC_MODE2 does not really need net_admin capability, but only sys_admin.
> > > >
> > > > Extract a new helper for it, it will be also used for the HID bpf
> > > > implementation.
> > > >
> > > > Cc: Sean Young <sean@mess.org>
> > > > Signed-off-by: Benjamin Tissoires <benjamin.tissoires@redhat.com>
> > > >
> > > > ---
> > > >
> > > > new in v2
> > > > ---
> > > >  kernel/bpf/syscall.c | 14 +++++++++++++-
> > > >  1 file changed, 13 insertions(+), 1 deletion(-)
> > > >
> > > > diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
> > > > index db402ebc5570..cc570891322b 100644
> > > > --- a/kernel/bpf/syscall.c
> > > > +++ b/kernel/bpf/syscall.c
> > > > @@ -2165,7 +2165,6 @@ static bool is_net_admin_prog_type(enum bpf_prog_type prog_type)
> > > >         case BPF_PROG_TYPE_LWT_SEG6LOCAL:
> > > >         case BPF_PROG_TYPE_SK_SKB:
> > > >         case BPF_PROG_TYPE_SK_MSG:
> > > > -       case BPF_PROG_TYPE_LIRC_MODE2:
> > > >         case BPF_PROG_TYPE_FLOW_DISSECTOR:
> > > >         case BPF_PROG_TYPE_CGROUP_DEVICE:
> > > >         case BPF_PROG_TYPE_CGROUP_SOCK:
> > > > @@ -2202,6 +2201,17 @@ static bool is_perfmon_prog_type(enum bpf_prog_type prog_type)
> > > >         }
> > > >  }
> > > >
> > > > +static bool is_sys_admin_prog_type(enum bpf_prog_type prog_type)
> > > > +{
> > > > +       switch (prog_type) {
> > > > +       case BPF_PROG_TYPE_LIRC_MODE2:
> > > > +       case BPF_PROG_TYPE_EXT: /* extends any prog */
> > > > +               return true;
> > > > +       default:
> > > > +               return false;
> > > > +       }
> > > > +}
> > >
> > > I am not sure whether we should do this. This is a behavior change, that may
> > > break some user space. Also, BPF_PROG_TYPE_EXT is checked in
> > > is_perfmon_prog_type(), and this change will make that case useless.
> >
> > Sure, I can drop it from v3 and make this function appear for HID only.
>
> For BPF_PROG_TYPE_LIRC_MODE2, I don't think this change will break userspace.
> This is called from ir-keytable(1) which is called from udev. It should have
> all the necessary permissions.
>
> In addition, the vast majority IR decoders are non-bpf. bpf ir decoders have
> very few users at the moment.
>
> I am working on completely new userspace tooling which will make extensive
> use of bpf ir decoding with full lircd and IRP compatibility, but this is not
> finished yet (see https://github.com/seanyoung/cir).

Thanks for these information. I guess change for BPF_PROG_TYPE_LIRC_MODE2
is ok then. Would you mind ack or review this change (either current version or
a later version)?

Thanks,
Song
Sean Young March 9, 2022, 8:27 a.m. UTC | #6
On Fri, Mar 04, 2022 at 06:28:25PM +0100, Benjamin Tissoires wrote:
> LIRC_MODE2 does not really need net_admin capability, but only sys_admin.
> 
> Extract a new helper for it, it will be also used for the HID bpf
> implementation.
> 
> Cc: Sean Young <sean@mess.org>
> Signed-off-by: Benjamin Tissoires <benjamin.tissoires@redhat.com>

For BPF_PROG_TYPE_LIRC_MODE2, I don't think this change will break userspace.
This is called from ir-keytable(1) which is called from udev. It should have
all the necessary permissions.

In addition, the vast majority IR decoders are non-bpf. bpf ir decoders have
very few users at the moment.

Acked-by: Sean Young <sean@mess.org>


Sean

> 
> ---
> 
> new in v2
> ---
>  kernel/bpf/syscall.c | 14 +++++++++++++-
>  1 file changed, 13 insertions(+), 1 deletion(-)
> 
> diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
> index db402ebc5570..cc570891322b 100644
> --- a/kernel/bpf/syscall.c
> +++ b/kernel/bpf/syscall.c
> @@ -2165,7 +2165,6 @@ static bool is_net_admin_prog_type(enum bpf_prog_type prog_type)
>  	case BPF_PROG_TYPE_LWT_SEG6LOCAL:
>  	case BPF_PROG_TYPE_SK_SKB:
>  	case BPF_PROG_TYPE_SK_MSG:
> -	case BPF_PROG_TYPE_LIRC_MODE2:
>  	case BPF_PROG_TYPE_FLOW_DISSECTOR:
>  	case BPF_PROG_TYPE_CGROUP_DEVICE:
>  	case BPF_PROG_TYPE_CGROUP_SOCK:
> @@ -2202,6 +2201,17 @@ static bool is_perfmon_prog_type(enum bpf_prog_type prog_type)
>  	}
>  }
>  
> +static bool is_sys_admin_prog_type(enum bpf_prog_type prog_type)
> +{
> +	switch (prog_type) {
> +	case BPF_PROG_TYPE_LIRC_MODE2:
> +	case BPF_PROG_TYPE_EXT: /* extends any prog */
> +		return true;
> +	default:
> +		return false;
> +	}
> +}
> +
>  /* last field in 'union bpf_attr' used by this command */
>  #define	BPF_PROG_LOAD_LAST_FIELD core_relo_rec_size
>  
> @@ -2252,6 +2262,8 @@ static int bpf_prog_load(union bpf_attr *attr, bpfptr_t uattr)
>  		return -EPERM;
>  	if (is_perfmon_prog_type(type) && !perfmon_capable())
>  		return -EPERM;
> +	if (is_sys_admin_prog_type(type) && !capable(CAP_SYS_ADMIN))
> +		return -EPERM;
>  
>  	/* attach_prog_fd/attach_btf_obj_fd can specify fd of either bpf_prog
>  	 * or btf, we need to check which one it is
> -- 
> 2.35.1
diff mbox series

Patch

diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
index db402ebc5570..cc570891322b 100644
--- a/kernel/bpf/syscall.c
+++ b/kernel/bpf/syscall.c
@@ -2165,7 +2165,6 @@  static bool is_net_admin_prog_type(enum bpf_prog_type prog_type)
 	case BPF_PROG_TYPE_LWT_SEG6LOCAL:
 	case BPF_PROG_TYPE_SK_SKB:
 	case BPF_PROG_TYPE_SK_MSG:
-	case BPF_PROG_TYPE_LIRC_MODE2:
 	case BPF_PROG_TYPE_FLOW_DISSECTOR:
 	case BPF_PROG_TYPE_CGROUP_DEVICE:
 	case BPF_PROG_TYPE_CGROUP_SOCK:
@@ -2202,6 +2201,17 @@  static bool is_perfmon_prog_type(enum bpf_prog_type prog_type)
 	}
 }
 
+static bool is_sys_admin_prog_type(enum bpf_prog_type prog_type)
+{
+	switch (prog_type) {
+	case BPF_PROG_TYPE_LIRC_MODE2:
+	case BPF_PROG_TYPE_EXT: /* extends any prog */
+		return true;
+	default:
+		return false;
+	}
+}
+
 /* last field in 'union bpf_attr' used by this command */
 #define	BPF_PROG_LOAD_LAST_FIELD core_relo_rec_size
 
@@ -2252,6 +2262,8 @@  static int bpf_prog_load(union bpf_attr *attr, bpfptr_t uattr)
 		return -EPERM;
 	if (is_perfmon_prog_type(type) && !perfmon_capable())
 		return -EPERM;
+	if (is_sys_admin_prog_type(type) && !capable(CAP_SYS_ADMIN))
+		return -EPERM;
 
 	/* attach_prog_fd/attach_btf_obj_fd can specify fd of either bpf_prog
 	 * or btf, we need to check which one it is