From cfa7b011894d689cccfa88a25da324fa5c34e4ed Mon Sep 17 00:00:00 2001 From: Joanne Koong Date: Wed, 1 Mar 2023 07:49:53 -0800 Subject: selftests/bpf: tests for using dynptrs to parse skb and xdp buffers Test skb and xdp dynptr functionality in the following ways: 1) progs/test_cls_redirect_dynptr.c * Rewrite "progs/test_cls_redirect.c" test to use dynptrs to parse skb data * This is a great example of how dynptrs can be used to simplify a lot of the parsing logic for non-statically known values. When measuring the user + system time between the original version vs. using dynptrs, and averaging the time for 10 runs (using "time ./test_progs -t cls_redirect"): original version: 0.092 sec with dynptrs: 0.078 sec 2) progs/test_xdp_dynptr.c * Rewrite "progs/test_xdp.c" test to use dynptrs to parse xdp data When measuring the user + system time between the original version vs. using dynptrs, and averaging the time for 10 runs (using "time ./test_progs -t xdp_attach"): original version: 0.118 sec with dynptrs: 0.094 sec 3) progs/test_l4lb_noinline_dynptr.c * Rewrite "progs/test_l4lb_noinline.c" test to use dynptrs to parse skb data When measuring the user + system time between the original version vs. using dynptrs, and averaging the time for 10 runs (using "time ./test_progs -t l4lb_all"): original version: 0.062 sec with dynptrs: 0.081 sec For number of processed verifier instructions: original version: 6268 insns with dynptrs: 2588 insns 4) progs/test_parse_tcp_hdr_opt_dynptr.c * Add sample code for parsing tcp hdr opt lookup using dynptrs. This logic is lifted from a real-world use case of packet parsing in katran [0], a layer 4 load balancer. The original version "progs/test_parse_tcp_hdr_opt.c" (not using dynptrs) is included here as well, for comparison. When measuring the user + system time between the original version vs. using dynptrs, and averaging the time for 10 runs (using "time ./test_progs -t parse_tcp_hdr_opt"): original version: 0.031 sec with dynptrs: 0.045 sec 5) progs/dynptr_success.c * Add test case "test_skb_readonly" for testing attempts at writes on a prog type with read-only skb ctx. * Add "test_dynptr_skb_data" for testing that bpf_dynptr_data isn't supported for skb progs. 6) progs/dynptr_fail.c * Add test cases "skb_invalid_data_slice{1,2,3,4}" and "xdp_invalid_data_slice{1,2}" for testing that helpers that modify the underlying packet buffer automatically invalidate the associated data slice. * Add test cases "skb_invalid_ctx" and "xdp_invalid_ctx" for testing that prog types that do not support bpf_dynptr_from_skb/xdp don't have access to the API. * Add test case "dynptr_slice_var_len{1,2}" for testing that variable-sized len can't be passed in to bpf_dynptr_slice * Add test case "skb_invalid_slice_write" for testing that writes to a read-only data slice are rejected by the verifier. * Add test case "data_slice_out_of_bounds_skb" for testing that writes to an area outside the slice are rejected. * Add test case "invalid_slice_rdwr_rdonly" for testing that prog types that don't allow writes to packet data don't accept any calls to bpf_dynptr_slice_rdwr. [0] https://github.com/facebookincubator/katran/blob/main/katran/lib/bpf/pckt_parsing.h Signed-off-by: Joanne Koong Acked-by: Andrii Nakryiko Link: https://lore.kernel.org/r/20230301154953.641654-11-joannelkoong@gmail.com Signed-off-by: Alexei Starovoitov --- tools/testing/selftests/bpf/progs/dynptr_fail.c | 287 +++++++++++++++++++++++- 1 file changed, 286 insertions(+), 1 deletion(-) (limited to 'tools/testing/selftests/bpf/progs/dynptr_fail.c') diff --git a/tools/testing/selftests/bpf/progs/dynptr_fail.c b/tools/testing/selftests/bpf/progs/dynptr_fail.c index aa5b69354b91..20ce920d891d 100644 --- a/tools/testing/selftests/bpf/progs/dynptr_fail.c +++ b/tools/testing/selftests/bpf/progs/dynptr_fail.c @@ -5,7 +5,9 @@ #include #include #include +#include #include "bpf_misc.h" +#include "bpf_kfuncs.h" char _license[] SEC("license") = "GPL"; @@ -244,6 +246,27 @@ done: return 0; } +/* A data slice can't be accessed out of bounds */ +SEC("?tc") +__failure __msg("value is outside of the allowed memory range") +int data_slice_out_of_bounds_skb(struct __sk_buff *skb) +{ + struct bpf_dynptr ptr; + struct ethhdr *hdr; + char buffer[sizeof(*hdr)] = {}; + + bpf_dynptr_from_skb(skb, 0, &ptr); + + hdr = bpf_dynptr_slice_rdwr(&ptr, 0, buffer, sizeof(buffer)); + if (!hdr) + return SK_DROP; + + /* this should fail */ + *(__u8*)(hdr + 1) = 1; + + return SK_PASS; +} + SEC("?raw_tp") __failure __msg("value is outside of the allowed memory range") int data_slice_out_of_bounds_map_value(void *ctx) @@ -399,7 +422,6 @@ int invalid_helper2(void *ctx) /* this should fail */ bpf_dynptr_read(read_data, sizeof(read_data), (void *)&ptr + 8, 0, 0); - return 0; } @@ -1044,6 +1066,193 @@ int dynptr_read_into_slot(void *ctx) return 0; } +/* bpf_dynptr_slice()s are read-only and cannot be written to */ +SEC("?tc") +__failure __msg("R0 cannot write into rdonly_mem") +int skb_invalid_slice_write(struct __sk_buff *skb) +{ + struct bpf_dynptr ptr; + struct ethhdr *hdr; + char buffer[sizeof(*hdr)] = {}; + + bpf_dynptr_from_skb(skb, 0, &ptr); + + hdr = bpf_dynptr_slice(&ptr, 0, buffer, sizeof(buffer)); + if (!hdr) + return SK_DROP; + + /* this should fail */ + hdr->h_proto = 1; + + return SK_PASS; +} + +/* The read-only data slice is invalidated whenever a helper changes packet data */ +SEC("?tc") +__failure __msg("invalid mem access 'scalar'") +int skb_invalid_data_slice1(struct __sk_buff *skb) +{ + struct bpf_dynptr ptr; + struct ethhdr *hdr; + char buffer[sizeof(*hdr)] = {}; + + bpf_dynptr_from_skb(skb, 0, &ptr); + + hdr = bpf_dynptr_slice(&ptr, 0, buffer, sizeof(buffer)); + if (!hdr) + return SK_DROP; + + val = hdr->h_proto; + + if (bpf_skb_pull_data(skb, skb->len)) + return SK_DROP; + + /* this should fail */ + val = hdr->h_proto; + + return SK_PASS; +} + +/* The read-write data slice is invalidated whenever a helper changes packet data */ +SEC("?tc") +__failure __msg("invalid mem access 'scalar'") +int skb_invalid_data_slice2(struct __sk_buff *skb) +{ + struct bpf_dynptr ptr; + struct ethhdr *hdr; + char buffer[sizeof(*hdr)] = {}; + + bpf_dynptr_from_skb(skb, 0, &ptr); + + hdr = bpf_dynptr_slice_rdwr(&ptr, 0, buffer, sizeof(buffer)); + if (!hdr) + return SK_DROP; + + hdr->h_proto = 123; + + if (bpf_skb_pull_data(skb, skb->len)) + return SK_DROP; + + /* this should fail */ + hdr->h_proto = 1; + + return SK_PASS; +} + +/* The read-only data slice is invalidated whenever bpf_dynptr_write() is called */ +SEC("?tc") +__failure __msg("invalid mem access 'scalar'") +int skb_invalid_data_slice3(struct __sk_buff *skb) +{ + char write_data[64] = "hello there, world!!"; + struct bpf_dynptr ptr; + struct ethhdr *hdr; + char buffer[sizeof(*hdr)] = {}; + + bpf_dynptr_from_skb(skb, 0, &ptr); + + hdr = bpf_dynptr_slice(&ptr, 0, buffer, sizeof(buffer)); + if (!hdr) + return SK_DROP; + + val = hdr->h_proto; + + bpf_dynptr_write(&ptr, 0, write_data, sizeof(write_data), 0); + + /* this should fail */ + val = hdr->h_proto; + + return SK_PASS; +} + +/* The read-write data slice is invalidated whenever bpf_dynptr_write() is called */ +SEC("?tc") +__failure __msg("invalid mem access 'scalar'") +int skb_invalid_data_slice4(struct __sk_buff *skb) +{ + char write_data[64] = "hello there, world!!"; + struct bpf_dynptr ptr; + struct ethhdr *hdr; + char buffer[sizeof(*hdr)] = {}; + + bpf_dynptr_from_skb(skb, 0, &ptr); + hdr = bpf_dynptr_slice_rdwr(&ptr, 0, buffer, sizeof(buffer)); + if (!hdr) + return SK_DROP; + + hdr->h_proto = 123; + + bpf_dynptr_write(&ptr, 0, write_data, sizeof(write_data), 0); + + /* this should fail */ + hdr->h_proto = 1; + + return SK_PASS; +} + +/* The read-only data slice is invalidated whenever a helper changes packet data */ +SEC("?xdp") +__failure __msg("invalid mem access 'scalar'") +int xdp_invalid_data_slice1(struct xdp_md *xdp) +{ + struct bpf_dynptr ptr; + struct ethhdr *hdr; + char buffer[sizeof(*hdr)] = {}; + + bpf_dynptr_from_xdp(xdp, 0, &ptr); + hdr = bpf_dynptr_slice(&ptr, 0, buffer, sizeof(buffer)); + if (!hdr) + return SK_DROP; + + val = hdr->h_proto; + + if (bpf_xdp_adjust_head(xdp, 0 - (int)sizeof(*hdr))) + return XDP_DROP; + + /* this should fail */ + val = hdr->h_proto; + + return XDP_PASS; +} + +/* The read-write data slice is invalidated whenever a helper changes packet data */ +SEC("?xdp") +__failure __msg("invalid mem access 'scalar'") +int xdp_invalid_data_slice2(struct xdp_md *xdp) +{ + struct bpf_dynptr ptr; + struct ethhdr *hdr; + char buffer[sizeof(*hdr)] = {}; + + bpf_dynptr_from_xdp(xdp, 0, &ptr); + hdr = bpf_dynptr_slice_rdwr(&ptr, 0, buffer, sizeof(buffer)); + if (!hdr) + return SK_DROP; + + hdr->h_proto = 9; + + if (bpf_xdp_adjust_head(xdp, 0 - (int)sizeof(*hdr))) + return XDP_DROP; + + /* this should fail */ + hdr->h_proto = 1; + + return XDP_PASS; +} + +/* Only supported prog type can create skb-type dynptrs */ +SEC("?raw_tp") +__failure __msg("calling kernel function bpf_dynptr_from_skb is not allowed") +int skb_invalid_ctx(void *ctx) +{ + struct bpf_dynptr ptr; + + /* this should fail */ + bpf_dynptr_from_skb(ctx, 0, &ptr); + + return 0; +} + /* Reject writes to dynptr slot for uninit arg */ SEC("?raw_tp") __failure __msg("potential write to dynptr at off=-16") @@ -1061,6 +1270,61 @@ int uninit_write_into_slot(void *ctx) return 0; } +/* Only supported prog type can create xdp-type dynptrs */ +SEC("?raw_tp") +__failure __msg("calling kernel function bpf_dynptr_from_xdp is not allowed") +int xdp_invalid_ctx(void *ctx) +{ + struct bpf_dynptr ptr; + + /* this should fail */ + bpf_dynptr_from_xdp(ctx, 0, &ptr); + + return 0; +} + +__u32 hdr_size = sizeof(struct ethhdr); +/* Can't pass in variable-sized len to bpf_dynptr_slice */ +SEC("?tc") +__failure __msg("unbounded memory access") +int dynptr_slice_var_len1(struct __sk_buff *skb) +{ + struct bpf_dynptr ptr; + struct ethhdr *hdr; + char buffer[sizeof(*hdr)] = {}; + + bpf_dynptr_from_skb(skb, 0, &ptr); + + /* this should fail */ + hdr = bpf_dynptr_slice(&ptr, 0, buffer, hdr_size); + if (!hdr) + return SK_DROP; + + return SK_PASS; +} + +/* Can't pass in variable-sized len to bpf_dynptr_slice */ +SEC("?tc") +__failure __msg("must be a known constant") +int dynptr_slice_var_len2(struct __sk_buff *skb) +{ + char buffer[sizeof(struct ethhdr)] = {}; + struct bpf_dynptr ptr; + struct ethhdr *hdr; + + bpf_dynptr_from_skb(skb, 0, &ptr); + + if (hdr_size <= sizeof(buffer)) { + /* this should fail */ + hdr = bpf_dynptr_slice_rdwr(&ptr, 0, buffer, hdr_size); + if (!hdr) + return SK_DROP; + hdr->h_proto = 12; + } + + return SK_PASS; +} + static int callback(__u32 index, void *data) { *(__u32 *)data = 123; @@ -1092,3 +1356,24 @@ int invalid_data_slices(void *ctx) return 0; } + +/* Program types that don't allow writes to packet data should fail if + * bpf_dynptr_slice_rdwr is called + */ +SEC("cgroup_skb/ingress") +__failure __msg("the prog does not allow writes to packet data") +int invalid_slice_rdwr_rdonly(struct __sk_buff *skb) +{ + char buffer[sizeof(struct ethhdr)] = {}; + struct bpf_dynptr ptr; + struct ethhdr *hdr; + + bpf_dynptr_from_skb(skb, 0, &ptr); + + /* this should fail since cgroup_skb doesn't allow + * changing packet data + */ + hdr = bpf_dynptr_slice_rdwr(&ptr, 0, buffer, sizeof(buffer)); + + return 0; +} -- cgit v1.2.3