From mboxrd@z Thu Jan 1 00:00:00 1970 Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.remote-ip=117.135.210.4 ARC-Seal: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; cv=none; t=1794191996; b=ZxGkhoh2vJw/+DW2EvjehyOrodCIAGUw3x5Fprt1hFv/HdmLrQzh5eFaqwWmEceizvui 1rblFAGi5mfo0JCd9MMDt1xYkgaKx16SfQZG+Y3KWjYXJHYKyE1WWRPIdOuPghayfbvjZ 9xB7b5i4e04le14S2EOUk96a+DpwVF18nQWvvxifoaUsUurZp88z+lgSghWkKAycIR5D1 JAGfyQ8NPPGrJccSTKNniCVrDhto1Djx9wV2XeJM7FM9LOZVUI6MW9aEO1nUfNaZcB58B oeju/V9k1efQdQ2qkvIZ1m3UydSTsFl4Wb4UySniY9/L8okqx0J5kNGg7kEwYVTRFnA== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1794191996; h=DMARC-Filter:DKIM-Signature:Received:From:To:Cc:Subject:Date: Message-Id:X-Mailer:In-Reply-To:References:MIME-Version: Content-Transfer-Encoding:X-CM-TRANSID:X-Coremail-Antispam: X-CM-SenderInfo; bh=+mJbsjGNpTwmspFtA59oea3AMA2Rwz9m7WEWR/Ry0aM=; b=iWv11kEOeFxvwyiK6fRLUoGl3As/AIsyF8FFT/LXfU1j1ILV9o3K3TGhLbzDWzGRJWL2 VvhCuDz90cfM33jXj/+AAuhCVmcJ5c0HEgxknBp0m9lZoFBopwZOlywEumFyGNL2eSgIX 0zpJyL0zIk10HaqBusDmeEZoSAd+cBbaf9FysH/e8GbMe6PxqvPhsYV+hI3bWpDLmx2e+ LmQH2lDCBTRDkhrgU3rSwCixhRLfHDcX7urjdJdSUlQUdfYqgkHBCw2Qt0Lgpy5tPzqLR c8gtGNGRha2NgsTWqrV6nqXHG2NiTwwqequfXpCszFQN804bL+DrhLHSO2j3pucY/Sw== ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass header.from=163.com; spf=pass smtp.mailfrom=163.com; dkim=pass header.d=163.com header.i=@163.com header.a=rsa-sha256 header.s=s110527 header.b=J0EUPcIt; arc=none smtp.remote-ip=117.135.210.4 Received: from m16.mail.163.com (m16.mail.163.com [117.135.210.4]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (prime256v1) server-digest SHA256) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 1838F606A31C; Mon, 9 Nov 2026 02:39:53 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.2 smtp.subspace.kernel.org 1838F606A31C Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=163.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=163.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=163.com header.i=@163.com header.a=rsa-sha256 header.s=s110527 header.b=J0EUPcIt DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=163.com; s=s110527; h=From:To:Subject:Date:Message-Id:MIME-Version; bh=+m JbsjGNpTwmspFtA59oea3AMA2Rwz9m7WEWR/Ry0aM=; b=J0EUPcIt7u6hr9zvD2 jtMm/HlO4oOqEsEnrQG0ekV4HqEYarUyv6i0DMkRrPfDyV9zK8xUxRotKKBM1UXd DE9jxLONXvJ7M+65RtL6kAZ5tyjePVZlLohp7lUjuFWjGoInJeDnmodSoWi2kn/+ sYKwjrboj5dxIwXT7fHgrsMME= Received: from localhost.localdomain (unknown []) by gzsmtp5 (Coremail) with SMTP id QCgvCgDnFIE_MvFquQguEw--.65376S4; Mon, 09 Nov 2026 10:38:56 +0800 (CST) From: Rongguang Wei To: netdev@vger.kernel.org, bpf@vger.kernel.org Cc: willemdebruijn.kernel@gmail.com, jasowangio@gmail.com, andrew+netdev@lunn.ch, davem@davemloft.net, kuba@kernel.org, ast@kernel.org, daniel@iogearbox.net, andrii@kernel.org, eddyz87@gmail.com, Rongguang Wei , Willem de Bruijn Subject: [PATCH net v10 2/2] selftests: net: add TAP socket filter attach tests Date: Mon, 9 Nov 2026 10:38:48 +0800 Message-Id: <20261109023848.59575-3-clementwei90@163.com> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20261109023848.59575-1-clementwei90@163.com> References: <20261109023848.59575-1-clementwei90@163.com> X-Mailing-List: netdev@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-CM-TRANSID:QCgvCgDnFIE_MvFquQguEw--.65376S4 X-Coremail-Antispam: 1Uf129KBjvJXoW3JF45GF43AryxXF1fJrW7twb_yoWfZFy8pa s5WayDGF1UXrW7Xws7ArW8uFWfAw4DGr15ZFs5K3s8Zr4DGryUua9akFWSkan2yr48uws0 kFyaya43WwsIqFJanT9S1TB71UUUUU7qnTZGkaVYY2UrUUUUjbIjqfuFe4nvWSU5nxnvy2 9KBjDUYxBIdaVFxhVjvjDU0xZFpf9x07jzNtcUUUUU= X-CM-SenderInfo: 5fohzv5qwzvxizq6il2tof0z/xtbC-QGzH2rxMkE-kAAA3X From: Rongguang Wei reattach_filter_without_user_buffer() attaches a filter, makes the buffer the program was copied from unreadable, detaches the queue and attaches it again. It then attaches a second queue from a fresh socket, which starts without a filter of its own, so a clear IFF_NOFILTER shows that the filter was installed again from the kernel copy. attach_filter_bad_len_keeps_program() checks that a TUNATTACHFILTER with a bad length leaves the installed program and the filter state that TUNGETIFF reports alone, and that a queue attached afterwards still gets the filter. attach_filter_bad_prog_keeps_program() refuses a program with a valid length and instructions that bpf_check_classic() rejects, and checks the same properties: the filter state on the queue, and a queue attached afterwards still gets the saved program. attach_filter_nofilter_flag() and detach_filter_clears_reattach() cover the ways to attach a queue without a filter. Signed-off-by: Rongguang Wei Reviewed-by: Willem de Bruijn --- tools/testing/selftests/net/tun.c | 249 ++++++++++++++++++++++++++++++ 1 file changed, 249 insertions(+) diff --git a/tools/testing/selftests/net/tun.c b/tools/testing/selftests/net/tun.c index 34de2580e32e..895d8d396d8a 100644 --- a/tools/testing/selftests/net/tun.c +++ b/tools/testing/selftests/net/tun.c @@ -9,9 +9,11 @@ #include #include #include +#include #include #include #include +#include #include #include "kselftest_harness.h" @@ -548,6 +550,253 @@ TEST_F(tun, reattach_close_delete) EXPECT_EQ(tun_delete(self->ifname), 0); } +/* accept: return skb->len. Three instructions on purpose, so that the + * length read back through TUNGETFILTER tells it apart from a rejected + * program that is shorter. + */ +static const struct sock_filter filter_accept[] = { + BPF_STMT(BPF_LD | BPF_W | BPF_LEN, 0), + BPF_STMT(BPF_ALU | BPF_ADD | BPF_K, 0), + BPF_STMT(BPF_RET | BPF_A, 0), +}; + +/* Put the instructions in an anonymous mapping, so that the test can make the + * address unreadable afterwards. + */ +static void *filter_alloc(const struct sock_filter *insns, unsigned int len) +{ + void *p; + + p = mmap(NULL, getpagesize(), PROT_READ | PROT_WRITE, + MAP_PRIVATE | MAP_ANONYMOUS, -1, 0); + if (p == MAP_FAILED) + return NULL; + + memcpy(p, insns, len * sizeof(*insns)); + + return p; +} + +static int filter_attach(int fd, const struct sock_filter *insns, unsigned int len) +{ + struct sock_fprog fp = { + .len = len, + .filter = (struct sock_filter *)insns, + }; + + return ioctl(fd, TUNATTACHFILTER, (void *)&fp); +} + +static int filter_get(int fd, struct sock_fprog *fp) +{ + return ioctl(fd, TUNGETFILTER, (void *)fp); +} + +static int tun_get_iff_flags(int fd) +{ + struct ifreq ifr = { 0 }; + + if (ioctl(fd, TUNGETIFF, (void *)&ifr) < 0) + return -1; + + return ifr.ifr_flags; +} + +/* + * A queue can be attached long after the filter was configured, from a + * process that does not necessarily map the buffer the program was copied + * from, so the kernel has to keep its own copy of the program. Here the + * mapping is made unreadable before the queue is attached again, and another + * queue is then attached from a fresh socket, which starts without a filter + * of its own. + */ +TEST_F(tun, reattach_filter_without_user_buffer) +{ + struct sock_fprog gf = { 0 }; + struct ifreq ifr = { 0 }; + short flags = 0; + void *prog; + int fd, ret; + + prog = filter_alloc(filter_accept, ARRAY_SIZE(filter_accept)); + ASSERT_NE(prog, NULL); + ASSERT_EQ(filter_attach(self->fd, prog, ARRAY_SIZE(filter_accept)), 0); + + EXPECT_EQ(tun_detach(self->fd, self->ifname), 0); + + /* This memory is no longer readable */ + ASSERT_EQ(mprotect(prog, getpagesize(), PROT_NONE), 0); + + ret = tun_attach(self->fd, self->ifname); + EXPECT_EQ(ret, 0); + + flags = tun_get_iff_flags(self->fd); + EXPECT_GE(flags, 0); + /* The queue is attached again, not left disabled */ + EXPECT_EQ(flags & IFF_DETACH_QUEUE, 0); + EXPECT_EQ(flags & IFF_NOFILTER, 0); + + /* The two checks below document the expected state, they cannot + * tell a reinstalled filter from no filter: tun_detach() leaves + * sk_filter alone, and TUNGETFILTER only returns the header. + */ + EXPECT_EQ(filter_get(self->fd, &gf), 0); + EXPECT_EQ(gf.len, ARRAY_SIZE(filter_accept)); + + /* A new queue starts without a filter, so a clear IFF_NOFILTER shows + * that the filter was installed again from the kernel copy. + */ + fd = open("/dev/net/tun", O_RDWR); + ASSERT_GE(fd, 0); + + strcpy(ifr.ifr_name, self->ifname); + ifr.ifr_flags = IFF_TAP | IFF_MULTI_QUEUE; + EXPECT_GE(ioctl(fd, TUNSETIFF, (void *)&ifr), 0); + + flags = tun_get_iff_flags(fd); + EXPECT_GE(flags, 0); + EXPECT_EQ(flags & IFF_NOFILTER, 0); + + close(fd); + + ASSERT_EQ(mprotect(prog, getpagesize(), PROT_READ | PROT_WRITE), 0); + ASSERT_EQ(munmap(prog, getpagesize()), 0); +} + +/* A new queue attached with IFF_NOFILTER must not get the filter that is + * configured on the device. + */ +TEST_F(tun, attach_filter_nofilter_flag) +{ + struct ifreq ifr = { 0 }; + short flags = 0; + int fd; + + ASSERT_EQ(filter_attach(self->fd, filter_accept, ARRAY_SIZE(filter_accept)), 0); + + fd = open("/dev/net/tun", O_RDWR); + ASSERT_GE(fd, 0); + + strcpy(ifr.ifr_name, self->ifname); + ifr.ifr_flags = IFF_TAP | IFF_MULTI_QUEUE | IFF_NOFILTER; + EXPECT_GE(ioctl(fd, TUNSETIFF, (void *)&ifr), 0); + + flags = tun_get_iff_flags(fd); + EXPECT_GE(flags, 0); + EXPECT_EQ(flags & IFF_NOFILTER, IFF_NOFILTER); + + close(fd); +} + +/* After TUNDETACHFILTER a later attach must not install the filter again */ +TEST_F(tun, detach_filter_clears_reattach) +{ + short flags = 0; + + ASSERT_EQ(filter_attach(self->fd, filter_accept, ARRAY_SIZE(filter_accept)), 0); + EXPECT_EQ(ioctl(self->fd, TUNDETACHFILTER, 0), 0); + + flags = tun_get_iff_flags(self->fd); + EXPECT_GE(flags, 0); + EXPECT_EQ(flags & IFF_NOFILTER, IFF_NOFILTER); + + EXPECT_EQ(tun_detach(self->fd, self->ifname), 0); + EXPECT_EQ(tun_attach(self->fd, self->ifname), 0); + + flags = tun_get_iff_flags(self->fd); + EXPECT_GE(flags, 0); + EXPECT_EQ(flags & IFF_NOFILTER, IFF_NOFILTER); +} + +/* A TUNATTACHFILTER with a bad length must leave the installed program and the + * filter state that TUNGETIFF reports alone. + */ +TEST_F(tun, attach_filter_bad_len_keeps_program) +{ + struct sock_fprog gf = { 0 }; + struct ifreq ifr = { 0 }; + short flags = 0; + int fd; + + ASSERT_EQ(filter_attach(self->fd, filter_accept, ARRAY_SIZE(filter_accept)), 0); + + errno = 0; + EXPECT_EQ(filter_attach(self->fd, filter_accept, 0), -1); + EXPECT_EQ(errno, EINVAL); + + EXPECT_EQ(filter_get(self->fd, &gf), 0); + EXPECT_EQ(gf.len, ARRAY_SIZE(filter_accept)); + + flags = tun_get_iff_flags(self->fd); + EXPECT_GE(flags, 0); + EXPECT_EQ(flags & IFF_NOFILTER, 0); + + /* A queue attached afterwards still gets the filter, so the rejected + * ioctl left the saved program and filter_attached alone. + */ + fd = open("/dev/net/tun", O_RDWR); + ASSERT_GE(fd, 0); + + strcpy(ifr.ifr_name, self->ifname); + ifr.ifr_flags = IFF_TAP | IFF_MULTI_QUEUE; + EXPECT_GE(ioctl(fd, TUNSETIFF, (void *)&ifr), 0); + + flags = tun_get_iff_flags(fd); + EXPECT_GE(flags, 0); + EXPECT_EQ(flags & IFF_NOFILTER, 0); + + close(fd); +} + +/* A TUNATTACHFILTER with instructions that bpf_check_classic() rejects must + * be refused, and must leave the program installed already in place. + */ +TEST_F(tun, attach_filter_bad_prog_keeps_program) +{ + struct sock_fprog gf = { 0 }; + struct sock_filter bad[] = { + BPF_STMT(BPF_LD | BPF_W | BPF_LEN, 0), + BPF_JUMP(BPF_JMP | BPF_JEQ | BPF_K, 0, 1, 0), + }; + struct ifreq ifr = { 0 }; + short flags = 0; + int fd; + + ASSERT_EQ(filter_attach(self->fd, filter_accept, + ARRAY_SIZE(filter_accept)), 0); + + errno = 0; + EXPECT_EQ(filter_attach(self->fd, bad, ARRAY_SIZE(bad)), -1); + EXPECT_EQ(errno, EINVAL); + + /* the program attached before is untouched */ + EXPECT_EQ(filter_get(self->fd, &gf), 0); + EXPECT_EQ(gf.len, ARRAY_SIZE(filter_accept)); + + /* IFF_NOFILTER comes from the socket's sk_filter, not from the saved + * header, so a clear flag shows the filter is still installed. + */ + flags = tun_get_iff_flags(self->fd); + EXPECT_GE(flags, 0); + EXPECT_EQ(flags & IFF_NOFILTER, 0); + + /* A queue attached afterwards still gets the filter, so the rejected + * program never replaced the saved one. + */ + fd = open("/dev/net/tun", O_RDWR); + ASSERT_GE(fd, 0); + + strcpy(ifr.ifr_name, self->ifname); + ifr.ifr_flags = IFF_TAP | IFF_MULTI_QUEUE; + EXPECT_GE(ioctl(fd, TUNSETIFF, (void *)&ifr), 0); + + flags = tun_get_iff_flags(fd); + EXPECT_GE(flags, 0); + EXPECT_EQ(flags & IFF_NOFILTER, 0); + + close(fd); +} + FIXTURE(tun_vnet_gso) { char ifname[IFNAMSIZ]; -- 2.25.1 No virus found Checked by Hillstone Network AntiVirus