From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (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 C3D6C32B125; Sat, 12 Sep 2026 19:44:42 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789242284; cv=none; b=oD/sxbZRe9ru1dGUnUbRQQota1LJ8HeY1aZmaymla/+i0IeVFxObs4DxUFBuXVpsCFfHO59B0/+et9Wb9fx88wXPCr4qWAwmnibGCmYMkXXXWM6dE7aBR8N6KdAbrXpAaUkjTLN5XMDFN6zJF04MmVsqWu6U3vvsAh4onNKYsXk= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789242284; c=relaxed/simple; bh=ksftsR3/VXi6/A7n4+6rDWF1kXyMnIu6txsxviQmwQI=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=dzX20l4wqHh4Lrm34sCuac0YKGWcxiEMfePz/IuGAu8LV+52xhj2S2Z3UlefgwqPERvRMiiUGI/7SIoDxqYvXupLrZzmI/l/gq2gTuS9mrkgCIyerknzrfg4cF47EdmPs1Fx3JsPCYC911gwUWCQAN9N1zVialLpi9Nn/j+Eie4= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=IVWh47wc; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="IVWh47wc" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 306A41F000FF; Sat, 12 Sep 2026 19:44:42 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1789242282; bh=fW2nYKrSO4SjZeEcuHVHMcnBc/u72u0kMrH5ZfTrz4Q=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=IVWh47wcNPP9d4w3FYrmPdmIaHKVSdmPvmeyKeksKFwMaplpGw0h2f+yjVL/jNKi/ tjvjs1rQPUW13AezAh+LVr/hZevKA4LcwHsSI/FQd5KSwvKBL0gPoJfKM73x0JjFwy pZEppaeEobisfwIBvwjNFDcug+Esp1YeXlYMzX/8= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Yinhao Hu , Kaiyan Mei , Dongliang Mu , Daniel Borkmann , Alexei Starovoitov , Sasha Levin , "Miguel Gazquez (Schneider Electric)" Subject: [PATCH 5.10 333/798] bpf: Enforce expected_attach_type for tailcall compatibility Date: Sat, 12 Sep 2026 08:59:21 +0200 Message-ID: <20260912065524.794497268@linuxfoundation.org> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20260912065516.948645775@linuxfoundation.org> References: <20260912065516.948645775@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 5.10-stable review patch. If anyone has any objections, please let me know. ------------------ From: Daniel Borkmann [ Upstream commit 4540aed51b12bc13364149bf95f6ecef013197c0 ] Yinhao et al. recently reported: Our fuzzer tool discovered an uninitialized pointer issue in the bpf_prog_test_run_xdp() function within the Linux kernel's BPF subsystem. This leads to a NULL pointer dereference when a BPF program attempts to deference the txq member of struct xdp_buff object. The test initializes two programs of BPF_PROG_TYPE_XDP: progA acts as the entry point for bpf_prog_test_run_xdp() and its expected_attach_type can neither be of be BPF_XDP_DEVMAP nor BPF_XDP_CPUMAP. progA calls into a slot of a tailcall map it owns. progB's expected_attach_type must be BPF_XDP_DEVMAP to pass xdp_is_valid_access() validation. The program returns struct xdp_md's egress_ifindex, and the latter is only allowed to be accessed under mentioned expected_attach_type. progB is then inserted into the tailcall which progA calls. The underlying issue goes beyond XDP though. Another example are programs of type BPF_PROG_TYPE_CGROUP_SOCK_ADDR. sock_addr_is_valid_access() as well as sock_addr_func_proto() have different logic depending on the programs' expected_attach_type. Similarly, a program attached to BPF_CGROUP_INET4_GETPEERNAME should not be allowed doing a tailcall into a program which calls bpf_bind() out of BPF which is only enabled for BPF_CGROUP_INET4_CONNECT. In short, specifying expected_attach_type allows to open up additional functionality or restrictions beyond what the basic bpf_prog_type enables. The use of tailcalls must not violate these constraints. Fix it by enforcing expected_attach_type in __bpf_prog_map_compatible(). Note that we only enforce this for tailcall maps, but not for BPF devmaps or cpumaps: There, the programs are invoked through dev_map_bpf_prog_run*() and cpu_map_bpf_prog_run*() which set up a new environment / context and therefore these situations are not prone to this issue. [ Fixed conflict, applied the changes to bpf_prog_array_compatible instead of __bpf_prog_map_compatible. Dropped the guard testing for BPF_MAP_TYPE_PROG_ARRAY as bpf_prog_array_compatible is only called on maps whose map_type is already BPF_MAP_TYPE_PROG_ARRAY, so the check was always true ] Fixes: 5e43f899b03a ("bpf: Check attach type at prog load time") Reported-by: Yinhao Hu Reported-by: Kaiyan Mei Reviewed-by: Dongliang Mu Signed-off-by: Daniel Borkmann Link: https://lore.kernel.org/r/20250926171201.188490-1-daniel@iogearbox.net Signed-off-by: Alexei Starovoitov Signed-off-by: Sasha Levin Signed-off-by: Miguel Gazquez (Schneider Electric) Signed-off-by: Sasha Levin --- include/linux/bpf.h | 1 + kernel/bpf/core.c | 4 ++++ 2 files changed, 5 insertions(+) diff --git a/include/linux/bpf.h b/include/linux/bpf.h index 5d5d0bc7ca50b..fb213524ccac1 100644 --- a/include/linux/bpf.h +++ b/include/linux/bpf.h @@ -876,6 +876,7 @@ struct bpf_array_aux { spinlock_t lock; enum bpf_prog_type type; bool jited; + enum bpf_attach_type expected_attach_type; } owner; /* Programs with direct jumps into programs part of this array. */ struct list_head poke_progs; diff --git a/kernel/bpf/core.c b/kernel/bpf/core.c index db613a97ee5f9..c9b3fe8b250ae 100644 --- a/kernel/bpf/core.c +++ b/kernel/bpf/core.c @@ -1795,10 +1795,14 @@ bool bpf_prog_array_compatible(struct bpf_array *array, */ array->aux->owner.type = fp->type; array->aux->owner.jited = fp->jited; + array->aux->owner.expected_attach_type = fp->expected_attach_type; ret = true; } else { ret = array->aux->owner.type == fp->type && array->aux->owner.jited == fp->jited; + if (ret && + array->aux->owner.expected_attach_type != fp->expected_attach_type) + ret = false; } spin_unlock(&array->aux->owner.lock); return ret; -- 2.53.0