From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 678C221CA13; Thu, 24 Apr 2025 09:46:47 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1745488008; cv=none; b=OMOuUc4A43KP05TyaU4lfA/Zl7MSw3tcU+xgoZY2grWLgC3iBomIrScaRE/c8l2XTR1t2IgK+zXD73IPd5O50MhH6vogRcutM0cBz+czH4SWvWF8R2CesMvq7usyO7kofFT4M/qsdKGG/BwEJ5FME5g1JQA2nAENisDgMS6U+7k= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1745488008; c=relaxed/simple; bh=kRBDJNaddAADD3tImUoxy3nO7YUIsqSB0eBE/RCv4Po=; h=From:To:Cc:Subject:In-Reply-To:References:Date:Message-ID: MIME-Version:Content-Type; b=Mtx0Pz5nMlCI9g6nU2PRDflycgLN+Sgil6s4PG1m8+cYWrmVR+Ydrk0Q9qLKT2/l2Nte4kpecyyXxBhMepAmdiS0A95kIc3+B25caQYjSw19R5eVgUnlh3fb5JmEfxP97fcwiDxlneUSV3uzR8BvwRDdyRbPLNZX5WfOK3yyxBc= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=Xz35h3k0; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="Xz35h3k0" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 99BF1C4CEEB; Thu, 24 Apr 2025 09:46:47 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1745488007; bh=kRBDJNaddAADD3tImUoxy3nO7YUIsqSB0eBE/RCv4Po=; h=From:To:Cc:Subject:In-Reply-To:References:Date:From; b=Xz35h3k0OZenF+jkvafY9OKecKxjHE4gH5kcKefli0aPtTyZZ1R6jNtVgr0O/9NqW Gm6bP9MuE+rEXMm5LDcyHiiyOdY/vcu2n/14F87FzklxD4ax518URFFHyNUPnUUfgN SEd5kZDX/v/yLKUWt7ixFx1t+puGEN1+Dv6L7z6a4muSiKRlbVjbXAYLk8vv51BNf6 nUWPHp1btKcE9AJcsD0Oy5Pl22mGlOfIwpphTVJhcdGBQp4vAZbHaukCYpud3p7dGX 5ilI92woP0yGEEaqM8WRpaj2rL/jJEYDoc2cs8mRTZI4CU0pPdnBWkTIIhI/GHk+Js P4SsoqoXjbgaw== Received: by alrua-x1.borgediget.toke.dk (Postfix, from userid 1000) id D13251A035DF; Thu, 24 Apr 2025 11:46:34 +0200 (CEST) From: Toke =?utf-8?Q?H=C3=B8iland-J=C3=B8rgensen?= To: Lorenzo Bianconi , Alexei Starovoitov , Daniel Borkmann , John Fastabend , Andrii Nakryiko , Martin KaFai Lau , Eduard Zingerman , Song Liu , Yonghong Song , KP Singh , Stanislav Fomichev , Hao Luo , Jiri Olsa , "David S. Miller" , Jakub Kicinski , Jesper Dangaard Brouer , Mykola Lysenko , Shuah Khan Cc: bpf@vger.kernel.org, netdev@vger.kernel.org, linux-kselftest@vger.kernel.org, Lorenzo Bianconi Subject: Re: [PATCH bpf-next v2] bpf: Allow XDP dev-bound programs to perform XDP_REDIRECT into maps In-Reply-To: <20250423-xdp-prog-bound-fix-v2-1-51742a5dfbce@kernel.org> References: <20250423-xdp-prog-bound-fix-v2-1-51742a5dfbce@kernel.org> X-Clacks-Overhead: GNU Terry Pratchett Date: Thu, 24 Apr 2025 11:46:34 +0200 Message-ID: <87wmb97uyt.fsf@toke.dk> Precedence: bulk X-Mailing-List: linux-kselftest@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain Lorenzo Bianconi writes: > 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 > --- > 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)) { Hmm, so this allows devbound programs in tail call maps, right? But there's no guarantee that a tail call map will always be used for a particular device, is there? For instance, it could be shared between multiple XDP programs, bound to different devices, thus getting the wrong kfunc. Or you could even have dev-bound programs tail-called from non-dev-bound programs with this change AFAICT? In other words, I think this is too relaxed, your change in v1 that only relaxed cpumap and devmap checks here was better. In fact, I don't really see why bpf_check_tail_call() needs to look at devmap/cpumap at all, so maybe just changing the map_type_contains_progs() call to only match tail call maps is better? -Toke