From patchwork Mon Jul 24 22:13:25 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Andrew Kanner X-Patchwork-Id: 13325375 X-Patchwork-Delegate: kuba@kernel.org Received: from lindbergh.monkeyblade.net (lindbergh.monkeyblade.net [23.128.96.19]) (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 3E776111A5 for ; Mon, 24 Jul 2023 22:14:23 +0000 (UTC) Received: from mail-lf1-x135.google.com (mail-lf1-x135.google.com [IPv6:2a00:1450:4864:20::135]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 60E2710EC; Mon, 24 Jul 2023 15:14:21 -0700 (PDT) Received: by mail-lf1-x135.google.com with SMTP id 2adb3069b0e04-4fdfefdf5abso463853e87.1; Mon, 24 Jul 2023 15:14:21 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20221208; t=1690236859; x=1690841659; h=content-transfer-encoding:mime-version:message-id:date:subject:cc :to:from:from:to:cc:subject:date:message-id:reply-to; bh=yAsZdb1l2a00omNbaFLi6X9Z1M8KVaOQyZOE0+c0Tbc=; b=hYUPPntxc6s6ZI4Cv6z9ft0y9WjAHYLbjp4SyKtPI00sUEkmzSHvNUNDypAdtXKVn7 ynUhu6KxwYHAZvUCNW+2HRJbaTFRlavjUeajGgTnONjK0MlNiaz5r1Y/geWjqRs1Q1rq KwrxAF55ex3j2qhvNLaDm9k6H78/5KU79/fipttlxE9I422PoXt70UVSBB8ey9ClHTr9 9ju9MM0jTVFy/FPIdtBqZbEYxjJMe5861wtQvpkW/htfOqRfHjGj1vkujcN+phTOa2jY fZTh60p+kt1nY5Jw7Y9wBB39JPD2XHqJuHEefozlnjfVXVqWATdaczWsvYN0K1BsJrjl oReQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20221208; t=1690236859; x=1690841659; h=content-transfer-encoding:mime-version:message-id:date:subject:cc :to:from:x-gm-message-state:from:to:cc:subject:date:message-id :reply-to; bh=yAsZdb1l2a00omNbaFLi6X9Z1M8KVaOQyZOE0+c0Tbc=; b=WqFX6LQsYfSuSrr6XvjYZzBe014m1JPKaKXnvqiVW61njLo1htHYA91Aq0tjNHRjCr 8zfOxlCaNiKEWmi5/pEK+M2Dh2iu3g0GDaBhaslNy6NfTGvF9XVoUr2+n1fC8ec5hmBU mc8U6X9i8OwQ/7EUxrbXW6CodVWHVGzR9oM3TnDC4dF1ZBf7swhQyWxnCxdyXg9mxqk0 nPoeVu9PSij6Gicj072L+iNsSeQ8S4/FAJzWpIUtUusNt1nb2/mGLXbiZaTl1XxjoCHO GUsJiNg805RcJ/zjvX44UbNwpy3IHpSvaMsxerrM78JjsvJSCV322rna2u49mIFAuivD E8vA== X-Gm-Message-State: ABy/qLZiQVJxtoXTS3ao11ih01AewU1UhoABGiIiU8bWWsv8DBlL/DlM oiKNf6yZ4PDpwH5chYnWDwI= X-Google-Smtp-Source: APBJJlHAx+uI4qxDU4os4KVjWZLmaw4hsPui/tQzNXMFfBkFTUJUsBeQZifK5GQTbHM+kZ5qOj9tyg== X-Received: by 2002:a05:6512:6d4:b0:4f9:58ed:7bba with SMTP id u20-20020a05651206d400b004f958ed7bbamr7337865lff.16.1690236859228; Mon, 24 Jul 2023 15:14:19 -0700 (PDT) Received: from localhost.localdomain ([77.222.25.78]) by smtp.gmail.com with ESMTPSA id v2-20020a056512048200b004fba077e654sm2401130lfq.194.2023.07.24.15.14.17 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 24 Jul 2023 15:14:18 -0700 (PDT) From: Andrew Kanner To: davem@davemloft.net, edumazet@google.com, kuba@kernel.org, pabeni@redhat.com, jasowang@redhat.com, netdev@vger.kernel.org, brouer@redhat.com, linux-kernel@vger.kernel.org Cc: linux-kernel-mentees@lists.linuxfoundation.org, syzbot+f817490f5bd20541b90a@syzkaller.appspotmail.com, Andrew Kanner Subject: [PATCH 1/2] drivers: net: use xdp only inside tun_build_skb() Date: Tue, 25 Jul 2023 01:13:25 +0300 Message-Id: <20230724221326.384-1-andrew.kanner@gmail.com> X-Mailer: git-send-email 2.39.3 Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Spam-Status: No, score=-2.1 required=5.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF,FREEMAIL_FROM, RCVD_IN_DNSWL_NONE,SPF_HELO_NONE,SPF_PASS,T_SCC_BODY_TEXT_LINE autolearn=ham autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on lindbergh.monkeyblade.net X-Patchwork-Delegate: kuba@kernel.org Syzkaller reported the following issue: ======================================= Too BIG xdp->frame_sz = 131072 WARNING: CPU: 0 PID: 5020 at net/core/filter.c:4121 ____bpf_xdp_adjust_tail net/core/filter.c:4121 [inline] WARNING: CPU: 0 PID: 5020 at net/core/filter.c:4121 bpf_xdp_adjust_tail+0x466/0xa10 net/core/filter.c:4103 ... Call Trace: bpf_prog_4add87e5301a4105+0x1a/0x1c __bpf_prog_run include/linux/filter.h:600 [inline] bpf_prog_run_xdp include/linux/filter.h:775 [inline] bpf_prog_run_generic_xdp+0x57e/0x11e0 net/core/dev.c:4721 netif_receive_generic_xdp net/core/dev.c:4807 [inline] do_xdp_generic+0x35c/0x770 net/core/dev.c:4866 tun_get_user+0x2340/0x3ca0 drivers/net/tun.c:1919 tun_chr_write_iter+0xe8/0x210 drivers/net/tun.c:2043 call_write_iter include/linux/fs.h:1871 [inline] new_sync_write fs/read_write.c:491 [inline] vfs_write+0x650/0xe40 fs/read_write.c:584 ksys_write+0x12f/0x250 fs/read_write.c:637 do_syscall_x64 arch/x86/entry/common.c:50 [inline] do_syscall_64+0x38/0xb0 arch/x86/entry/common.c:80 entry_SYSCALL_64_after_hwframe+0x63/0xcd frame_sz < PAGE_SIZE check was introduced in commit c8741e2bfe87 ("xdp: Allow bpf_xdp_adjust_tail() to grow packet size"). But tun_get_user() still provides an execution path to exceed XDP limits for packet size. The way to mitigate this is to reduce xdp to be used only in tun_build_skb(), without falling in tun_alloc_skb(), etc. Reported-and-tested-by: syzbot+f817490f5bd20541b90a@syzkaller.appspotmail.com Closes: https://lore.kernel.org/all/000000000000774b9205f1d8a80d@google.com/T/ Link: https://syzkaller.appspot.com/bug?id=5335c7c62bfff89bbb1c8f14cdabebe91909060f Signed-off-by: Andrew Kanner --- drivers/net/tun.c | 14 ++++++++------ 1 file changed, 8 insertions(+), 6 deletions(-) diff --git a/drivers/net/tun.c b/drivers/net/tun.c index d75456adc62a..18ccbbe9830a 100644 --- a/drivers/net/tun.c +++ b/drivers/net/tun.c @@ -1580,8 +1580,14 @@ static void tun_rx_batched(struct tun_struct *tun, struct tun_file *tfile, } static bool tun_can_build_skb(struct tun_struct *tun, struct tun_file *tfile, - int len, int noblock, bool zerocopy) + int len, int noblock, bool zerocopy, int *skb_xdp) { + if (SKB_DATA_ALIGN(len + TUN_RX_PAD) + + SKB_DATA_ALIGN(sizeof(struct skb_shared_info)) > PAGE_SIZE) { + *skb_xdp = 0; + return false; + } + if ((tun->flags & TUN_TYPE_MASK) != IFF_TAP) return false; @@ -1594,10 +1600,6 @@ static bool tun_can_build_skb(struct tun_struct *tun, struct tun_file *tfile, if (zerocopy) return false; - if (SKB_DATA_ALIGN(len + TUN_RX_PAD) + - SKB_DATA_ALIGN(sizeof(struct skb_shared_info)) > PAGE_SIZE) - return false; - return true; } @@ -1809,7 +1811,7 @@ static ssize_t tun_get_user(struct tun_struct *tun, struct tun_file *tfile, zerocopy = true; } - if (!frags && tun_can_build_skb(tun, tfile, len, noblock, zerocopy)) { + if (tun_can_build_skb(tun, tfile, len, noblock, zerocopy, &skb_xdp) && !frags) { /* For the packet that is not easy to be processed * (e.g gso or jumbo packet), we will do it at after * skb was created with generic XDP routine.