From patchwork Sat Feb 1 00:14:25 2025 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Kuniyuki Iwashima X-Patchwork-Id: 13955973 X-Patchwork-Delegate: bpf@iogearbox.net Received: from smtp-fw-80006.amazon.com (smtp-fw-80006.amazon.com [99.78.197.217]) (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 9D38BA934; Sat, 1 Feb 2025 00:14:42 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=99.78.197.217 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1738368884; cv=none; b=Oxe2YF6BLIBAn/1i5poqJfkZ8cqXpRfuxQr/wkn1ixGPZAmdrRHTtMi8+RvIfZ007ZCI3TYoOimUsb3wUnh525PwAGqotSL6hxMbEIb1h4jMgy/HB465L2uPOVKg9l+eR0cidUVhZ8pwLX9puxGHOaQAd44lDBwaz1rtX5hUidc= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1738368884; c=relaxed/simple; bh=fwnPzvWrESrUPkCcA2My4tpFwSxEPdl2EJtuTfU8I5U=; h=From:To:CC:Subject:Date:Message-ID:MIME-Version:Content-Type; b=G9fIO4MBfwV8PZuzcfUxUWIkODPnt+SD5ubJXIMsyrSd5zYbj6g7gCesNAdz1vcFLOONg29rzT79LDhREafxynsl+EefDe1Y4IltIHXEHu++CwBx3o4XsdCNxYeunucadoF2beH2k32mlf1/U+DZbggPPaUP3GDZg5iei1zswSc= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=amazon.com; spf=pass smtp.mailfrom=amazon.co.jp; dkim=pass (1024-bit key) header.d=amazon.com header.i=@amazon.com header.b=kQ75sP5e; arc=none smtp.client-ip=99.78.197.217 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=amazon.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=amazon.co.jp Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=amazon.com header.i=@amazon.com header.b="kQ75sP5e" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=amazon.com; i=@amazon.com; q=dns/txt; s=amazon201209; t=1738368883; x=1769904883; h=from:to:cc:subject:date:message-id:mime-version: content-transfer-encoding; bh=e5rvXHN34xl/8zzTp4uIrYXRbwAvVp16cloemZaHGrk=; b=kQ75sP5ekgE0soKNBSMRfteiYw3LHsSBkT3yxh0p9xERuq5XpAU8UXFa vSFH9IC/zLjUy+modM2iX90yZ42z9itRDjz/IuNirt2UrbDfWutYeAh+D jY3OuT2jTebu4+AVLaJZ4h064AC5qCDSO2H0qQy8DuW18iKt17odxWhmj c=; X-IronPort-AV: E=Sophos;i="6.13,250,1732579200"; d="scan'208";a="18826589" Received: from pdx4-co-svc-p1-lb2-vlan3.amazon.com (HELO smtpout.prod.us-west-2.prod.farcaster.email.amazon.dev) ([10.25.36.214]) by smtp-border-fw-80006.pdx80.corp.amazon.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 01 Feb 2025 00:14:41 +0000 Received: from EX19MTAUWB001.ant.amazon.com [10.0.38.20:49824] by smtpin.naws.us-west-2.prod.farcaster.email.amazon.dev [10.0.32.120:2525] with esmtp (Farcaster) id 4d3b26dc-c124-4b2f-874e-b369b79ea4c8; Sat, 1 Feb 2025 00:14:40 +0000 (UTC) X-Farcaster-Flow-ID: 4d3b26dc-c124-4b2f-874e-b369b79ea4c8 Received: from EX19D004ANA001.ant.amazon.com (10.37.240.138) by EX19MTAUWB001.ant.amazon.com (10.250.64.248) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA) id 15.2.1258.39; Sat, 1 Feb 2025 00:14:40 +0000 Received: from 6c7e67bfbae3.amazon.com (10.106.101.33) by EX19D004ANA001.ant.amazon.com (10.37.240.138) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA) id 15.2.1258.39; Sat, 1 Feb 2025 00:14:37 +0000 From: Kuniyuki Iwashima To: Martin KaFai Lau , Alexei Starovoitov , Daniel Borkmann , Andrii Nakryiko CC: Kuniyuki Iwashima , Kuniyuki Iwashima , , , "Yan Zhai" Subject: [PATCH v1 bpf] net: Annotate rx_sk with __nullable for trace_kfree_skb. Date: Fri, 31 Jan 2025 16:14:25 -0800 Message-ID: <20250201001425.42377-1-kuniyu@amazon.com> X-Mailer: git-send-email 2.39.5 (Apple Git-154) Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-ClientProxiedBy: EX19D045UWC001.ant.amazon.com (10.13.139.223) To EX19D004ANA001.ant.amazon.com (10.37.240.138) X-Patchwork-Delegate: bpf@iogearbox.net Yan Zhai reported a BPF prog could trigger a null-ptr-deref [0] in trace_kfree_skb if the prog does not check if rx_sk is NULL. Commit c53795d48ee8 ("net: add rx_sk to trace_kfree_skb") added rx_sk to trace_kfree_skb, but rx_sk is optional and could be NULL. Let's add __nullable suffix to rx_sk to let the BPF verifier validate such a prog and prevent the issue. Now we fail to load such a prog: libbpf: prog 'drop': -- BEGIN PROG LOAD LOG -- 0: R1=ctx() R10=fp0 ; int BPF_PROG(drop, struct sk_buff *skb, void *location, @ kfree_skb_sk_null.bpf.c:21 0: (79) r3 = *(u64 *)(r1 +24) func 'kfree_skb' arg3 has btf_id 5253 type STRUCT 'sock' 1: R1=ctx() R3_w=trusted_ptr_or_null_sock(id=1) ; bpf_printk("sk: %d, %d\n", sk, sk->__sk_common.skc_family); @ kfree_skb_sk_null.bpf.c:24 1: (69) r4 = *(u16 *)(r3 +16) R3 invalid mem access 'trusted_ptr_or_null_' processed 2 insns (limit 1000000) max_states_per_insn 0 total_states 0 peak_states 0 mark_read 0 -- END PROG LOAD LOG -- Note this fix requires commit 8aeaed21befc ("bpf: Support __nullable argument suffix for tp_btf"). [0]: BUG: kernel NULL pointer dereference, address: 0000000000000010 PF: supervisor read access in kernel mode PF: error_code(0x0000) - not-present page PGD 0 P4D 0 PREEMPT SMP CPU: 6 UID: 0 PID: 348 Comm: sshd Not tainted 6.12.11 #206 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.16.2-debian-1.16.2-1 04/01/2014 RIP: 0010:bpf_prog_5e21a6db8fcff1aa_drop+0x10/0x2d Code: cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc 0f 1f 44 00 00 0f 1f 00 55 48 89 e5 48 8b 57 18 <48> 0f b7 4a 10 48 bf 0c 4f e2 c1 ad 90 ff ff be 0c 00 00 00 e8 0f RSP: 0018:ffffa86640b53da8 EFLAGS: 00010202 RAX: 0000000000000001 RBX: ffffa866402d1000 RCX: 0000000000000002 RDX: 0000000000000000 RSI: ffffa866402d1048 RDI: ffffa86640b53dc8 RBP: ffffa86640b53da8 R08: 0000000000000000 R09: 9c908cd09b9c8c91 R10: ffff90adc056b540 R11: 0000000000000002 R12: 0000000000000000 R13: ffffa86640b53e88 R14: 0000000000000800 R15: fffffffffffffffe FS: 00007f2a27c2b480(0000) GS:ffff90b0efd00000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 0000000000000010 CR3: 0000000100e69004 CR4: 00000000001726f0 Call Trace: ? __die+0x1f/0x60 ? page_fault_oops+0x148/0x420 ? search_bpf_extables+0x5b/0x70 ? fixup_exception+0x27/0x2c0 ? exc_page_fault+0x75/0x170 ? asm_exc_page_fault+0x22/0x30 ? bpf_prog_5e21a6db8fcff1aa_drop+0x10/0x2d bpf_trace_run4+0x68/0xd0 ? unix_stream_connect+0x1f4/0x6f0 sk_skb_reason_drop+0x90/0x120 unix_stream_connect+0x1f4/0x6f0 __sys_connect+0x7f/0xb0 __x64_sys_connect+0x14/0x20 do_syscall_64+0x47/0xc30 entry_SYSCALL_64_after_hwframe+0x4b/0x53 RIP: 0033:0x7f2a27f296a0 Code: 00 f7 d8 64 89 01 48 83 c8 ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 80 3d 41 ff 0c 00 00 74 17 b8 2a 00 00 00 0f 05 <48> 3d 00 f0 ff ff 77 58 c3 0f 1f 80 00 00 00 00 48 83 ec 18 89 54 RSP: 002b:00007ffe29274f58 EFLAGS: 00000202 ORIG_RAX: 000000000000002a Fixes: c53795d48ee8 ("net: add rx_sk to trace_kfree_skb") Reported-by: Yan Zhai Closes: https://lore.kernel.org/netdev/Z50zebTRzI962e6X@debian.debian/ Signed-off-by: Kuniyuki Iwashima Tested-by: Yan Zhai --- include/trace/events/skb.h | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) diff --git a/include/trace/events/skb.h b/include/trace/events/skb.h index b877133cd93a..8bf0e61b8549 100644 --- a/include/trace/events/skb.h +++ b/include/trace/events/skb.h @@ -24,9 +24,9 @@ DEFINE_DROP_REASON(FN, FN) TRACE_EVENT(kfree_skb, TP_PROTO(struct sk_buff *skb, void *location, - enum skb_drop_reason reason, struct sock *rx_sk), + enum skb_drop_reason reason, struct sock *rx_sk__nullable), - TP_ARGS(skb, location, reason, rx_sk), + TP_ARGS(skb, location, reason, rx_sk__nullable), TP_STRUCT__entry( __field(void *, skbaddr) @@ -39,7 +39,7 @@ TRACE_EVENT(kfree_skb, TP_fast_assign( __entry->skbaddr = skb; __entry->location = location; - __entry->rx_sk = rx_sk; + __entry->rx_sk = rx_sk__nullable; __entry->protocol = ntohs(skb->protocol); __entry->reason = reason; ),