From patchwork Fri Jul 26 15:39:51 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Patchwork-Submitter: Leon Hwang X-Patchwork-Id: 13742910 X-Patchwork-Delegate: bpf@iogearbox.net Received: from out-180.mta0.migadu.com (out-180.mta0.migadu.com [91.218.175.180]) (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 2C78E6AAD for ; Fri, 26 Jul 2024 15:41:27 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=91.218.175.180 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1722008490; cv=none; b=b8JVpoiJE1tU6hvdWwfWQGvcMACicWR3tK/s2INUvObx6k9TPd/U/v/QT0FLyJP00fD/k9H9T0QjPB4RJxTs2Erj4AxG5MmbOmWdCRrrQSOZOMjuxe62QaIIfbIsaoTHs7+9z+EkU6Kogj2Z+aiLanfwSNCnPrKfF93DT2zFbWw= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1722008490; c=relaxed/simple; bh=A2aPMidMO5qC8X6JRaymk3SCwlQ+xpdNs1R9JI05fVE=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version:Content-Type; b=VFRQrb79WW6vHzkqN99FkbfOSVROyEuS9u7PuglQdSbSIQjoB3YUEeYN68Vr+q5i35hFT3mNJQbZO+6VtJtZxCUPAPdxhkTwPWWuhQOSYYV3zcTXmbTIvZGLuBtDxEGybuqhwIRMQM9XwnQZOzOPhB6NdU9+yld08XFbVeJV82U= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev; spf=pass smtp.mailfrom=linux.dev; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b=oVOoWqPG; arc=none smtp.client-ip=91.218.175.180 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.dev Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b="oVOoWqPG" X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1722008486; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=GRKlrtZf2VuphCg2iJ0UOE9qgqRNeX7MvFmJZ77pESU=; b=oVOoWqPGYCxUyhtEOyg36Qrmbv+UkID3gEQcdw+bYbjW48PWNZYNiv2JxtOUC3n9oksNGy uVp+4lQpmFSrCDMy2IFZ8/6SrLSXEhQob2/0ZoYhE92C9WII3XGAG+WExd7i/wuJfhZRHQ ddq1zsXM9dkz9S+k6l79uHAo5C+eaqs= From: Leon Hwang To: bpf@vger.kernel.org Cc: ast@kernel.org, daniel@iogearbox.net, andrii@kernel.org, toke@redhat.com, martin.lau@kernel.org, eddyz87@gmail.com, yonghong.song@linux.dev, wutengda@huaweicloud.com, leon.hwang@linux.dev, kernel-patches-bot@fb.com Subject: [PATCH bpf-next v2 1/2] bpf: Fix updating attached freplace prog to prog_array map Date: Fri, 26 Jul 2024 23:39:51 +0800 Message-ID: <20240726153952.76914-2-leon.hwang@linux.dev> In-Reply-To: <20240726153952.76914-1-leon.hwang@linux.dev> References: <20240726153952.76914-1-leon.hwang@linux.dev> Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Migadu-Flow: FLOW_OUT X-Patchwork-Delegate: bpf@iogearbox.net The commit f7866c3587337731 ("bpf: Fix null pointer dereference in resolve_prog_type() for BPF_PROG_TYPE_EXT") fixed a NULL pointer dereference panic, but didn't fix the issue that fails to update attached freplace prog to prog_array map. Since commit 1c123c567fb138eb ("bpf: Resolve fext program type when checking map compatibility"), freplace prog and its target prog are able to tail call each other. And the commit 3aac1ead5eb6b76f ("bpf: Move prog->aux->linked_prog and trampoline into bpf_link on attach") sets prog->aux->dst_prog as NULL after attaching freplace prog to its target prog. Then, as for following example: tailcall_freplace.c: // SPDX-License-Identifier: GPL-2.0 \#include \#include struct { __uint(type, BPF_MAP_TYPE_PROG_ARRAY); __uint(max_entries, 1); __uint(key_size, sizeof(__u32)); __uint(value_size, sizeof(__u32)); } jmp_table SEC(".maps"); int count = 0; SEC("freplace") int entry_freplace(struct __sk_buff *skb) { count++; bpf_tail_call_static(skb, &jmp_table, 0); return count; } char __license[] SEC("license") = "GPL"; tc_bpf2bpf.c: // SPDX-License-Identifier: GPL-2.0 \#include \#include __noinline int subprog(struct __sk_buff *skb) { volatile int ret = 1; asm volatile (""::"r+"(ret)); return ret; } SEC("tc") int entry_tc(struct __sk_buff *skb) { return subprog(skb); } char __license[] SEC("license") = "GPL"; And entry_freplace's target is the entry_tc's subprog. After loading entry_freplace, the jmp_table's owner type is BPF_PROG_TYPE_SCHED_CLS. Next, after attaching entry_freplace to entry_tc's subprog, its prog->aux-> dst_prog is NULL. Next, while updating entry_freplace to jmp_table, bpf_prog_map_compatible() returns false because resolve_prog_type() returns BPF_PROG_TYPE_EXT instead of BPF_PROG_TYPE_SCHED_CLS. With this patch, resolve_prog_type() returns BPF_PROG_TYPE_SCHED_CLS to support updating the attached entry_freplace to jmp_table. Fixes: f7866c358733 ("bpf: Fix null pointer dereference in resolve_prog_type() for BPF_PROG_TYPE_EXT") Cc: Toke Høiland-Jørgensen Cc: Martin KaFai Lau Signed-off-by: Leon Hwang Acked-by: Yonghong Song --- include/linux/bpf_verifier.h | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/include/linux/bpf_verifier.h b/include/linux/bpf_verifier.h index 5cea15c81b8a8..bfd093ac333f2 100644 --- a/include/linux/bpf_verifier.h +++ b/include/linux/bpf_verifier.h @@ -874,8 +874,8 @@ static inline u32 type_flag(u32 type) /* only use after check_attach_btf_id() */ static inline enum bpf_prog_type resolve_prog_type(const struct bpf_prog *prog) { - return (prog->type == BPF_PROG_TYPE_EXT && prog->aux->dst_prog) ? - prog->aux->dst_prog->type : prog->type; + return (prog->type == BPF_PROG_TYPE_EXT && prog->aux->saved_dst_prog_type) ? + prog->aux->saved_dst_prog_type : prog->type; } static inline bool bpf_prog_check_recur(const struct bpf_prog *prog)