From patchwork Wed Jul 3 08:39:31 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Geliang Tang X-Patchwork-Id: 13721523 X-Patchwork-Delegate: bpf@iogearbox.net 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 CEC5231A89; Wed, 3 Jul 2024 08:39:46 +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=1719995986; cv=none; b=N1/FXtYOrVb3etq350qfu7PxLFhVphOorThiEFxrbHeq3NnUmxbjD5nIvAxBzWh/y3k4cwa806QWLGBdlS0zTMB3HdJ+svlWD/KjtvlugmWjwu/6ypuzFGmgZwZH5psB/eHG4jtK4rJepUvX+ifMCYlMAzJd67Vickvhb3x0Iks= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1719995986; c=relaxed/simple; bh=lbbO2Mjjk3C5FS60AtyK2KRk/mhWt/0lX7ynZChERpg=; h=From:To:Cc:Subject:Date:Message-ID:MIME-Version; b=YWz9L+mnL3v5ECj1x8DJKAanes6OUycebsUWLGl/urdi9c62yKf0V3FqW5tHg7NVb5MAUONElUHyjfbb8pOvdN2WKYldXfzp3MZ6YDYoTH/Yvx059PBtTxrFzf01qMBhPdY+ftiN+aTDc6/FiwO9gxybxdfYa5b4Vj6xfSV/fGw= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=EofhSv7o; 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="EofhSv7o" Received: by smtp.kernel.org (Postfix) with ESMTPSA id C076DC2BD10; Wed, 3 Jul 2024 08:39:37 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1719995986; bh=lbbO2Mjjk3C5FS60AtyK2KRk/mhWt/0lX7ynZChERpg=; h=From:To:Cc:Subject:Date:From; b=EofhSv7oZoF7lvMXoOmA3s+tKwPh1UvvnoR12UgcUDNbFAUwHdS+AAxqCJFOALCZr AAN8LNG7zVwhjPM6+QeUlaxT2DAxalPQU4yJB2zeOLzb9Qe/4aqqFJhHXCxyjRBC03 WgO3aK62tYI3E1d8uFk5PRvXQ5yxGXBeBe52Nwr52HeS/XUDLkdm/QH31Vtu4KnvI1 4WdiE4k+Oi6/6LKcHEsSDGmoi6LA1L8MZeLvNPfVa2Gel55UgOlLlDpLjDUv47w78c haV6Upoui0WELXPiq2zBIzofIygwCItgPSYJe+3u2Bd2Iq4gALLEo2UDM3y4BdUL8S NEMWYIGC8TNWQ== From: Geliang Tang To: John Fastabend , Jakub Sitnicki , "David S. Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , Alexei Starovoitov , Daniel Borkmann Cc: Geliang Tang , David Ahern , Eduard Zingerman , Mykola Lysenko , Martin KaFai Lau , Song Liu , Yonghong Song , KP Singh , Stanislav Fomichev , Hao Luo , Jiri Olsa , Shuah Khan , Mykyta Yatsenko , Miao Xu , Yuran Pereira , Huacai Chen , Tiezhu Yang , "D . Wythe" , netdev@vger.kernel.org, bpf@vger.kernel.org, linux-kselftest@vger.kernel.org Subject: [PATCH net v5] skmsg: skip zero length skb in sk_msg_recvmsg Date: Wed, 3 Jul 2024 16:39:31 +0800 Message-ID: X-Mailer: git-send-email 2.43.0 Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Patchwork-Delegate: kuba@kernel.org From: Geliang Tang Run this BPF selftests (./test_progs -t sockmap_basic) on a Loongarch platform, a kernel panic occurs: ''' Oops[#1]: CPU: 22 PID: 2824 Comm: test_progs Tainted: G OE 6.10.0-rc2+ #18 Hardware name: LOONGSON Dabieshan/Loongson-TC542F0, BIOS Loongson-UDK2018 ... ... ra: 90000000048bf6c0 sk_msg_recvmsg+0x120/0x560 ERA: 9000000004162774 copy_page_to_iter+0x74/0x1c0 CRMD: 000000b0 (PLV0 -IE -DA +PG DACF=CC DACM=CC -WE) PRMD: 0000000c (PPLV0 +PIE +PWE) EUEN: 00000007 (+FPE +SXE +ASXE -BTE) ECFG: 00071c1d (LIE=0,2-4,10-12 VS=7) ESTAT: 00010000 [PIL] (IS= ECode=1 EsubCode=0) BADV: 0000000000000040 PRID: 0014c011 (Loongson-64bit, Loongson-3C5000) Modules linked in: bpf_testmod(OE) xt_CHECKSUM xt_MASQUERADE xt_conntrack Process test_progs (pid: 2824, threadinfo=0000000000863a31, task=...) Stack : ... ... Call Trace: [<9000000004162774>] copy_page_to_iter+0x74/0x1c0 [<90000000048bf6c0>] sk_msg_recvmsg+0x120/0x560 [<90000000049f2b90>] tcp_bpf_recvmsg_parser+0x170/0x4e0 [<90000000049aae34>] inet_recvmsg+0x54/0x100 [<900000000481ad5c>] sock_recvmsg+0x7c/0xe0 [<900000000481e1a8>] __sys_recvfrom+0x108/0x1c0 [<900000000481e27c>] sys_recvfrom+0x1c/0x40 [<9000000004c076ec>] do_syscall+0x8c/0xc0 [<9000000003731da4>] handle_syscall+0xc4/0x160 Code: ... ---[ end trace 0000000000000000 ]--- Kernel panic - not syncing: Fatal exception Kernel relocated by 0x3510000 .text @ 0x9000000003710000 .data @ 0x9000000004d70000 .bss @ 0x9000000006469400 ---[ end Kernel panic - not syncing: Fatal exception ]--- ''' This crash happens every time when running sockmap_skb_verdict_shutdown subtest in sockmap_basic. This crash is because a NULL pointer is passed to page_address() in sk_msg_recvmsg(). Due to the difference implementations depending on the architecture, page_address(NULL) will trigger a panic on Loongarch platform but not on X86 platform. So this bug was hidden on X86 platform for a while, but now it is exposed on Loongarch platform. The root cause is a zero length skb (skb->len == 0) is put on the queue. This zero length skb is a TCP FIN packet, which is sent by shutdown(), invoked in test_sockmap_skb_verdict_shutdown(): shutdown(p1, SHUT_WR); In this case, in sk_psock_skb_ingress_enqueue(), num_sge is zero, and no page is put to this sge (see sg_set_page in sg_set_page), but this empty sge is queued into ingress_msg list. And in sk_msg_recvmsg(), this empty sge is used, and a NULL page is got by sg_page(sge). Pass this NULL page to copy_page_to_iter(), which passes it to kmap_local_page() and to page_address(), then kernel panics. To solve this, we should skip this zero length skb. So in sk_msg_recvmsg(), if copy is zero, that means it's a zero length skb, skip invoking copy_page_to_iter(). We are using the EFAULT return triggered by copy_page_to_iter to check for is_fin in tcp_bpf.c. Fixes: 604326b41a6f ("bpf, sockmap: convert to generic sk_msg interface") Suggested-by: John Fastabend Signed-off-by: Geliang Tang Reviewed-by: John Fastabend --- v5: - update v5 as John suggested. - skmsg: skip zero length skb in sk_msg_recvmsg v4: - skmsg: skip empty sge in sk_msg_recvmsg v3: - skmsg: prevent empty ingress skb from enqueuing v2: - skmsg: null check for sg_page in sk_msg_recvmsg --- net/core/skmsg.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/net/core/skmsg.c b/net/core/skmsg.c index fd20aae30be2..bbf40b999713 100644 --- a/net/core/skmsg.c +++ b/net/core/skmsg.c @@ -434,7 +434,8 @@ int sk_msg_recvmsg(struct sock *sk, struct sk_psock *psock, struct msghdr *msg, page = sg_page(sge); if (copied + copy > len) copy = len - copied; - copy = copy_page_to_iter(page, sge->offset, copy, iter); + if (copy) + copy = copy_page_to_iter(page, sge->offset, copy, iter); if (!copy) { copied = copied ? copied : -EFAULT; goto out;