Add a test that attaches an xdp.frags program which shrinks a whole frag away, so bpf_xdp_shrink_data() frees a page_pool frag.
test_tun triggers the page-type mismatch on the generic XDP path. test_veth triggers the same mismatch on the veth path. test_veth_tx bounces the cow'd buff with XDP_TX so the peer runs a frags program on the resulting frame, covering the buff -> frame -> buff path. A kernel without the fix will report "Bad page state ... page_pool leak". The packet sizes only leave a frag after the cow on 4K pages, so the subtests skip elsewhere. Signed-off-by: Jiayuan Chen <[email protected]> --- .../bpf/prog_tests/xdp_shrink_frags.c | 288 ++++++++++++++++++ .../selftests/bpf/progs/xdp_shrink_frags.c | 34 +++ 2 files changed, 322 insertions(+) create mode 100644 tools/testing/selftests/bpf/prog_tests/xdp_shrink_frags.c create mode 100644 tools/testing/selftests/bpf/progs/xdp_shrink_frags.c diff --git a/tools/testing/selftests/bpf/prog_tests/xdp_shrink_frags.c b/tools/testing/selftests/bpf/prog_tests/xdp_shrink_frags.c new file mode 100644 index 0000000000000..ee8f9034a2684 --- /dev/null +++ b/tools/testing/selftests/bpf/prog_tests/xdp_shrink_frags.c @@ -0,0 +1,288 @@ +// SPDX-License-Identifier: GPL-2.0 +#include <test_progs.h> +#include <network_helpers.h> +#include <linux/if_tun.h> +#include <linux/if_ether.h> +#include <sys/uio.h> +#include <net/if.h> +#include <arpa/inet.h> +#include "xdp_shrink_frags.skel.h" + +/* + * A generic-XDP program that shrinks into the frags frees a page_pool frag. + * skb-backed XDP first cow's the nonlinear skb into page_pool memory + * (skb_cow_data_for_xdp() for generic XDP, skb_pp_cow_data() for veth), but + * the shared rxq is registered as MEM_TYPE_PAGE_SHARED, so a buggy kernel + * frees the frag with page_frag_free() -> "Bad page state ... page_pool leak". + */ + +#define TAP_NAME "xdp_shrink0" +#define TAP_NETNS "xdp_shrink_tap" + +#define NS_NAME_MAX_LEN 32 +#define VETH_LOCAL "xdp_shrinkA" +#define VETH_PEER "xdp_shrinkB" +#define VETH_LOCAL_IP "10.9.9.1" +#define VETH_PEER_IP "10.9.9.2" +#define VETH_LOCAL_MAC "02:00:00:00:00:01" + +/* + * skb_pp_cow_data() keeps up to one page in the linear part, so the packet + * sizes below only leave a frag (smaller than the 3000-byte shrink, so it is + * released as a whole) on 4K pages. Skip elsewhere rather than run a test + * that cannot tell a fixed kernel from a buggy one. + */ +#define PAGE_SIZE_4K 4096 + +/* + * Generous, so a loaded CI does not fail the assert prematurely; normally + * the first check already succeeds. + */ +#define WAIT_ITERS 10000 +#define WAIT_US 1000 + +static void wait_for_prog(struct xdp_shrink_frags *skel) +{ + int i; + + for (i = 0; i < WAIT_ITERS && !skel->bss->shrink_ran; i++) + usleep(WAIT_US); +} + +static int create_tap_napi_frags(const char *ifname) +{ + struct ifreq ifr = { + .ifr_flags = IFF_TAP | IFF_NO_PI | IFF_NAPI | IFF_NAPI_FRAGS, + }; + int fd, err; + + strscpy(ifr.ifr_name, ifname); + + fd = open("/dev/net/tun", O_RDWR); + if (fd < 0) + return -errno; + + err = ioctl(fd, TUNSETIFF, &ifr); + if (err) { + err = -errno; + close(fd); + return err; + } + + return fd; +} + +/* + * Similar to flow_dissector.c: writev() an IFF_NAPI_FRAGS tap to build a + * nonlinear skb that tun runs through do_xdp_generic(). + */ +static void test_tun(struct xdp_shrink_frags *skel) +{ + __u8 head[74], frag1[2048], frag2[2048]; + struct ethhdr *eth = (void *)head; + int tap_fd = -1, ifindex, err; + struct netns_obj *ns = NULL; + struct iovec iov[3]; + ssize_t n; + + if (getpagesize() != PAGE_SIZE_4K) { + test__skip(); + return; + } + + ns = netns_new(TAP_NETNS, true); + if (!ASSERT_OK_PTR(ns, "netns_new")) + return; + + tap_fd = create_tap_napi_frags(TAP_NAME); + if (!ASSERT_GE(tap_fd, 0, "create_tap")) + goto out; + + SYS(out, "ip link set dev " TAP_NAME " up"); + + ifindex = if_nametoindex(TAP_NAME); + if (!ASSERT_GT(ifindex, 0, "if_nametoindex")) + goto out; + + skel->bss->shrink_ran = 0; + + err = bpf_xdp_attach(ifindex, bpf_program__fd(skel->progs.xdp_shrink), + 0, NULL); + if (!ASSERT_OK(err, "bpf_xdp_attach")) + goto out; + + memset(head, 0, sizeof(head)); + memset(frag1, 0x41, sizeof(frag1)); + memset(frag2, 0x42, sizeof(frag2)); + eth->h_proto = htons(ETH_P_IP); + + iov[0].iov_base = head; iov[0].iov_len = sizeof(head); + iov[1].iov_base = frag1; iov[1].iov_len = sizeof(frag1); + iov[2].iov_base = frag2; iov[2].iov_len = sizeof(frag2); + + n = writev(tap_fd, iov, ARRAY_SIZE(iov)); + ASSERT_EQ(n, sizeof(head) + sizeof(frag1) + sizeof(frag2), "writev"); + + wait_for_prog(skel); + /* a buggy kernel only splats "page_pool leak", it does not fail here */ + ASSERT_GT(skel->bss->shrink_ran, 0, "xdp_prog_ran"); + + bpf_xdp_detach(ifindex, 0, NULL); +out: + if (tap_fd >= 0) + close(tap_fd); + netns_free(ns); +} + +/* + * Both veth ends live in their own namespace, so the traffic really crosses + * the pair and nothing is created in the caller's namespace. + */ +static int veth_setup(char *ns0, char *ns1) +{ + if (!ASSERT_OK(append_tid(ns0, NS_NAME_MAX_LEN), "append_tid ns0")) + return -1; + if (!ASSERT_OK(append_tid(ns1, NS_NAME_MAX_LEN), "append_tid ns1")) + return -1; + + SYS(fail, "ip netns add %s", ns0); + SYS(fail_ns0, "ip netns add %s", ns1); + SYS(fail_ns1, "ip -n %s link add %s mtu 8000 type veth peer name %s mtu 8000", + ns0, VETH_LOCAL, VETH_PEER); + SYS(fail_ns1, "ip -n %s link set %s netns %s", ns0, VETH_PEER, ns1); + SYS(fail_ns1, "ip -n %s link set %s address %s", ns0, VETH_LOCAL, + VETH_LOCAL_MAC); + SYS(fail_ns1, "ip -n %s addr add %s/24 dev %s", ns0, VETH_LOCAL_IP, + VETH_LOCAL); + SYS(fail_ns1, "ip -n %s link set %s up", ns0, VETH_LOCAL); + SYS(fail_ns1, "ip -n %s addr add %s/24 dev %s", ns1, VETH_PEER_IP, + VETH_PEER); + SYS(fail_ns1, "ip -n %s link set %s up", ns1, VETH_PEER); + + return 0; + +fail_ns1: + SYS_NOFAIL("ip netns del %s", ns1); +fail_ns0: + SYS_NOFAIL("ip netns del %s", ns0); +fail: + return -1; +} + +static void veth_cleanup(const char *ns0, const char *ns1) +{ + /* Dropping the namespaces takes the veth pair and its XDP programs. */ + SYS_NOFAIL("ip netns del %s", ns1); + SYS_NOFAIL("ip netns del %s", ns0); +} + +static int veth_attach(const char *ns, const char *dev, int prog_fd) +{ + struct nstoken *nstoken; + int ifindex, err; + + nstoken = open_netns(ns); + if (!ASSERT_OK_PTR(nstoken, "open_netns")) + return -1; + + ifindex = if_nametoindex(dev); + if (!ASSERT_GT(ifindex, 0, "if_nametoindex")) { + close_netns(nstoken); + return -1; + } + + err = bpf_xdp_attach(ifindex, prog_fd, 0, NULL); + close_netns(nstoken); + + return ASSERT_OK(err, "bpf_xdp_attach") ? 0 : -1; +} + +/* A large ping builds a nonlinear skb that veth cow's into its page_pool. */ +static void test_veth(struct xdp_shrink_frags *skel) +{ + char ns0[NS_NAME_MAX_LEN] = "xdp_shrink_ns0-"; + char ns1[NS_NAME_MAX_LEN] = "xdp_shrink_ns1-"; + + if (getpagesize() != PAGE_SIZE_4K) { + test__skip(); + return; + } + + if (veth_setup(ns0, ns1)) + return; + + skel->bss->shrink_ran = 0; + + if (veth_attach(ns0, VETH_LOCAL, bpf_program__fd(skel->progs.xdp_shrink))) + goto out; + + SYS_NOFAIL("ip netns exec %s ping -q -s 5000 -c 3 -W 1 %s", + ns1, VETH_LOCAL_IP); + + wait_for_prog(skel); + /* a buggy kernel only splats "page_pool leak", it does not fail here */ + ASSERT_GT(skel->bss->shrink_ran, 0, "xdp_prog_ran"); +out: + veth_cleanup(ns0, ns1); +} + +/* + * LOCAL cow's the incoming skb and returns XDP_TX, so the buff is turned into + * an xdp_frame and bounced to PEER, which shrinks a frag. A page_pool tag + * recorded on the buff must not leak into the frame, or PEER frees a plain + * page (whose pp was already cleared on the XDP_TX side) as page_pool memory. + */ +static void test_veth_tx(struct xdp_shrink_frags *skel) +{ + char ns0[NS_NAME_MAX_LEN] = "xdp_shrink_tx0-"; + char ns1[NS_NAME_MAX_LEN] = "xdp_shrink_tx1-"; + + if (getpagesize() != PAGE_SIZE_4K) { + test__skip(); + return; + } + + if (veth_setup(ns0, ns1)) + return; + + /* + * LOCAL bounces everything (incl. ARP) with XDP_TX, so pin a static + * neighbour to let the ping's payload actually reach it. + */ + SYS(out, "ip -n %s neigh add %s lladdr %s dev %s nud permanent", + ns1, VETH_LOCAL_IP, VETH_LOCAL_MAC, VETH_PEER); + + skel->bss->shrink_ran = 0; + + if (veth_attach(ns0, VETH_LOCAL, bpf_program__fd(skel->progs.xdp_tx))) + goto out; + if (veth_attach(ns1, VETH_PEER, bpf_program__fd(skel->progs.xdp_shrink))) + goto out; + + SYS_NOFAIL("ip netns exec %s ping -q -s 5000 -c 3 -W 1 %s", + ns1, VETH_LOCAL_IP); + + wait_for_prog(skel); + /* a buggy kernel only splats "page_pool leak", it does not fail here */ + ASSERT_GT(skel->bss->shrink_ran, 0, "xdp_prog_ran"); +out: + veth_cleanup(ns0, ns1); +} + +void test_xdp_shrink_frags(void) +{ + struct xdp_shrink_frags *skel; + + skel = xdp_shrink_frags__open_and_load(); + if (!ASSERT_OK_PTR(skel, "skel_open_load")) + return; + + if (test__start_subtest("tun")) + test_tun(skel); + if (test__start_subtest("veth")) + test_veth(skel); + if (test__start_subtest("veth_tx")) + test_veth_tx(skel); + + xdp_shrink_frags__destroy(skel); +} diff --git a/tools/testing/selftests/bpf/progs/xdp_shrink_frags.c b/tools/testing/selftests/bpf/progs/xdp_shrink_frags.c new file mode 100644 index 0000000000000..ad895ab699303 --- /dev/null +++ b/tools/testing/selftests/bpf/progs/xdp_shrink_frags.c @@ -0,0 +1,34 @@ +// SPDX-License-Identifier: GPL-2.0 +#include "vmlinux.h" +#include <bpf/bpf_helpers.h> + +int shrink_ran; + +SEC("xdp.frags") +int xdp_shrink(struct xdp_md *ctx) +{ + /* + * Runs on both skb-backed XDP paths (generic XDP via tun, and veth): + * the nonlinear skb is cow'd into page_pool memory before we run, so + * shrinking the tail releases a whole frag that has to go back to that + * pool. The counter only tells us the program ran and the helper + * succeeded -- a linear buff returns 0 as well -- it does not prove a + * frag was released. + */ + if (bpf_xdp_adjust_tail(ctx, -3000) == 0) + __sync_fetch_and_add(&shrink_ran, 1); + return XDP_PASS; +} + +SEC("xdp.frags") +int xdp_tx(struct xdp_md *ctx) +{ + /* + * Bounce the frame back. On veth this turns the buff into an + * xdp_frame, which is where a buff-scoped page_pool tag must not leak + * into the frame handed to the peer. + */ + return XDP_TX; +} + +char _license[] SEC("license") = "GPL"; -- 2.43.0
