netdev - Re: [PATCH bpf-next v2] bpf: Allow XDP dev-bound programs to perform XDP

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives
Hash Suite: Windows password security audit tool. GUI, reports in PDF.
[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Message-ID: <aAqmzAU1smXkRX84@lore-rh-laptop>
Date: Thu, 24 Apr 2025 23:02:04 +0200
From: Lorenzo Bianconi <lorenzo@...nel.org>
To: Jesper Dangaard Brouer <hawk@...nel.org>
Cc: Alexei Starovoitov <ast@...nel.org>,
	Daniel Borkmann <daniel@...earbox.net>,
	John Fastabend <john.fastabend@...il.com>,
	Andrii Nakryiko <andrii@...nel.org>,
	Martin KaFai Lau <martin.lau@...ux.dev>,
	Eduard Zingerman <eddyz87@...il.com>, Song Liu <song@...nel.org>,
	Yonghong Song <yonghong.song@...ux.dev>,
	KP Singh <kpsingh@...nel.org>, Stanislav Fomichev <sdf@...ichev.me>,
	Hao Luo <haoluo@...gle.com>, Jiri Olsa <jolsa@...nel.org>,
	"David S. Miller" <davem@...emloft.net>,
	Jakub Kicinski <kuba@...nel.org>, Mykola Lysenko <mykolal@...com>,
	Shuah Khan <shuah@...nel.org>, bpf@...r.kernel.org,
	netdev@...r.kernel.org, linux-kselftest@...r.kernel.org
Subject: Re: [PATCH bpf-next v2] bpf: Allow XDP dev-bound programs to perform
 XDP_REDIRECT into maps

On Apr 24, Jesper Dangaard Brouer wrote:
> 
> 
> On 23/04/2025 19.44, Lorenzo Bianconi wrote:
> > In the current implementation if the program is dev-bound to a specific
> > device, it will not be possible to perform XDP_REDIRECT into a DEVMAP
> > or CPUMAP even if the program is running in the driver NAPI context and
> > it is not attached to any map entry. This seems in contrast with the
> > explanation available in bpf_prog_map_compatible routine.
> > Fix the issue introducing __bpf_prog_map_compatible utility routine in
> > order to avoid bpf_prog_is_dev_bound() check running bpf_check_tail_call()
> > at program load time (bpf_prog_select_runtime()).
> > Continue forbidding to attach a dev-bound program to XDP maps
> > (BPF_MAP_TYPE_PROG_ARRAY, BPF_MAP_TYPE_DEVMAP and BPF_MAP_TYPE_CPUMAP).
> > 
> > Fixes: 3d76a4d3d4e59 ("bpf: XDP metadata RX kfuncs")
> > Signed-off-by: Lorenzo Bianconi<lorenzo@...nel.org>
> > ---
> > Changes in v2:
> > - Introduce __bpf_prog_map_compatible() utility routine in order to skip
> >    bpf_prog_is_dev_bound check in bpf_check_tail_call()
> > - Extend xdp_metadata selftest
> > - Link to v1:https://lore.kernel.org/r/20250422-xdp-prog-bound-fix-v1-1-0b581fa186fe@kernel.org
> > ---
> >   kernel/bpf/core.c                                  | 27 +++++++++++++---------
> >   .../selftests/bpf/prog_tests/xdp_metadata.c        | 22 +++++++++++++++++-
> >   tools/testing/selftests/bpf/progs/xdp_metadata.c   | 13 +++++++++++
> >   3 files changed, 50 insertions(+), 12 deletions(-)
> > 
> > diff --git a/kernel/bpf/core.c b/kernel/bpf/core.c
> > index ba6b6118cf504041278d05417c4212d57be6fca0..a3e571688421196c3ceaed62b3b59b62a0258a8c 100644
> > --- a/kernel/bpf/core.c
> > +++ b/kernel/bpf/core.c
> > @@ -2358,8 +2358,8 @@ static unsigned int __bpf_prog_ret0_warn(const void *ctx,
> >   	return 0;
> >   }
> > -bool bpf_prog_map_compatible(struct bpf_map *map,
> > -			     const struct bpf_prog *fp)
> > +static bool __bpf_prog_map_compatible(struct bpf_map *map,
> > +				      const struct bpf_prog *fp)
> >   {
> >   	enum bpf_prog_type prog_type = resolve_prog_type(fp);
> >   	bool ret;
> > @@ -2368,14 +2368,6 @@ bool bpf_prog_map_compatible(struct bpf_map *map,
> >   	if (fp->kprobe_override)
> >   		return false;
> > -	/* XDP programs inserted into maps are not guaranteed to run on
> > -	 * a particular netdev (and can run outside driver context entirely
> > -	 * in the case of devmap and cpumap). Until device checks
> > -	 * are implemented, prohibit adding dev-bound programs to program maps.
> > -	 */
> > -	if (bpf_prog_is_dev_bound(aux))
> > -		return false;
> > -
> >   	spin_lock(&map->owner.lock);
> >   	if (!map->owner.type) {
> >   		/* There's no owner yet where we could check for
> > @@ -2409,6 +2401,19 @@ bool bpf_prog_map_compatible(struct bpf_map *map,
> >   	return ret;
> >   }
> > +bool bpf_prog_map_compatible(struct bpf_map *map, const struct bpf_prog *fp)
> > +{
> > +	/* XDP programs inserted into maps are not guaranteed to run on
> > +	 * a particular netdev (and can run outside driver context entirely
> > +	 * in the case of devmap and cpumap). Until device checks
> > +	 * are implemented, prohibit adding dev-bound programs to program maps.
> > +	 */
> > +	if (bpf_prog_is_dev_bound(fp->aux))
> > +		return false;
> > +
> > +	return __bpf_prog_map_compatible(map, fp);
> > +}
> > +
> >   static int bpf_check_tail_call(const struct bpf_prog *fp)
> >   {
> >   	struct bpf_prog_aux *aux = fp->aux;
> > @@ -2421,7 +2426,7 @@ static int bpf_check_tail_call(const struct bpf_prog *fp)
> >   		if (!map_type_contains_progs(map))
> >   			continue;
> > -		if (!bpf_prog_map_compatible(map, fp)) {
> > +		if (!__bpf_prog_map_compatible(map, fp)) {
> >   			ret = -EINVAL;
> >   			goto out;
> >   		}
> 
> Does this change allow us to have a dev_bound BPF-prog that have
> tail-call BPF-progs that are not dev_bound?
> 
> The use-case is a dev_bound BPF-prog that reads e.g. HW vlan, store this in
> data_meta (or a per CPU array), and then tail-calls another BPF-prog that
> reads the data stored (from data_meta area). Maybe this is already supported
> before?

I think this patch allows a dev-bound program to run hw-metadata kfuncs and
perform XDP_REDIRECT into a prog_array but you will not be able to read these
info via hw-metadata kfuncs in a tail-call program since just dev-bound
programs are currently allowed to do that (and you can't insert a dev-bound
programs in BPF_MAP_TYPE_PROG_ARRAY).

Regards,
Lorenzo

> 
> --Jesper

Download attachment "signature.asc" of type "application/pgp-signature" (229 bytes)