From 600c70bad6594cb124c641ed05355ca134650ea4 Mon Sep 17 00:00:00 2001 From: Stanislav Fomichev Date: Mon, 1 Jul 2019 10:38:39 -0700 Subject: [PATCH 1/3] bpf: allow wide (u64) aligned stores for some fields of bpf_sock_addr Since commit cd17d7770578 ("bpf/tools: sync bpf.h") clang decided that it can do a single u64 store into user_ip6[2] instead of two separate u32 ones: # 17: (18) r2 = 0x100000000000000 # ; ctx->user_ip6[2] = bpf_htonl(DST_REWRITE_IP6_2); # 19: (7b) *(u64 *)(r1 +16) = r2 # invalid bpf_context access off=16 size=8 >From the compiler point of view it does look like a correct thing to do, so let's support it on the kernel side. Credit to Andrii Nakryiko for a proper implementation of bpf_ctx_wide_store_ok. Cc: Andrii Nakryiko Cc: Yonghong Song Fixes: cd17d7770578 ("bpf/tools: sync bpf.h") Reported-by: kernel test robot Acked-by: Yonghong Song Acked-by: Andrii Nakryiko Signed-off-by: Stanislav Fomichev Signed-off-by: Daniel Borkmann --- include/linux/filter.h | 6 ++++++ include/uapi/linux/bpf.h | 6 +++--- net/core/filter.c | 22 ++++++++++++++-------- 3 files changed, 23 insertions(+), 11 deletions(-) diff --git a/include/linux/filter.h b/include/linux/filter.h index 1fe53e78c7e3..6d944369ca87 100644 --- a/include/linux/filter.h +++ b/include/linux/filter.h @@ -747,6 +747,12 @@ bpf_ctx_narrow_access_ok(u32 off, u32 size, u32 size_default) return size <= size_default && (size & (size - 1)) == 0; } +#define bpf_ctx_wide_store_ok(off, size, type, field) \ + (size == sizeof(__u64) && \ + off >= offsetof(type, field) && \ + off + sizeof(__u64) <= offsetofend(type, field) && \ + off % sizeof(__u64) == 0) + #define bpf_classic_proglen(fprog) (fprog->len * sizeof(fprog->filter[0])) static inline void bpf_prog_lock_ro(struct bpf_prog *fp) diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h index ead27aebf491..c318385aba51 100644 --- a/include/uapi/linux/bpf.h +++ b/include/uapi/linux/bpf.h @@ -3247,7 +3247,7 @@ struct bpf_sock_addr { __u32 user_ip4; /* Allows 1,2,4-byte read and 4-byte write. * Stored in network byte order. */ - __u32 user_ip6[4]; /* Allows 1,2,4-byte read an 4-byte write. + __u32 user_ip6[4]; /* Allows 1,2,4-byte read and 4,8-byte write. * Stored in network byte order. */ __u32 user_port; /* Allows 4-byte read and write. @@ -3256,10 +3256,10 @@ struct bpf_sock_addr { __u32 family; /* Allows 4-byte read, but no write */ __u32 type; /* Allows 4-byte read, but no write */ __u32 protocol; /* Allows 4-byte read, but no write */ - __u32 msg_src_ip4; /* Allows 1,2,4-byte read an 4-byte write. + __u32 msg_src_ip4; /* Allows 1,2,4-byte read and 4-byte write. * Stored in network byte order. */ - __u32 msg_src_ip6[4]; /* Allows 1,2,4-byte read an 4-byte write. + __u32 msg_src_ip6[4]; /* Allows 1,2,4-byte read and 4,8-byte write. * Stored in network byte order. */ __bpf_md_ptr(struct bpf_sock *, sk); diff --git a/net/core/filter.c b/net/core/filter.c index 089aaea0ccc6..4481e950f020 100644 --- a/net/core/filter.c +++ b/net/core/filter.c @@ -6890,6 +6890,16 @@ static bool sock_addr_is_valid_access(int off, int size, if (!bpf_ctx_narrow_access_ok(off, size, size_default)) return false; } else { + if (bpf_ctx_wide_store_ok(off, size, + struct bpf_sock_addr, + user_ip6)) + return true; + + if (bpf_ctx_wide_store_ok(off, size, + struct bpf_sock_addr, + msg_src_ip6)) + return true; + if (size != size_default) return false; } @@ -7730,9 +7740,6 @@ static u32 xdp_convert_ctx_access(enum bpf_access_type type, /* SOCK_ADDR_STORE_NESTED_FIELD_OFF() has semantic similar to * SOCK_ADDR_LOAD_NESTED_FIELD_SIZE_OFF() but for store operation. * - * It doesn't support SIZE argument though since narrow stores are not - * supported for now. - * * In addition it uses Temporary Field TF (member of struct S) as the 3rd * "register" since two registers available in convert_ctx_access are not * enough: we can't override neither SRC, since it contains value to store, nor @@ -7740,7 +7747,7 @@ static u32 xdp_convert_ctx_access(enum bpf_access_type type, * instructions. But we need a temporary place to save pointer to nested * structure whose field we want to store to. */ -#define SOCK_ADDR_STORE_NESTED_FIELD_OFF(S, NS, F, NF, OFF, TF) \ +#define SOCK_ADDR_STORE_NESTED_FIELD_OFF(S, NS, F, NF, SIZE, OFF, TF) \ do { \ int tmp_reg = BPF_REG_9; \ if (si->src_reg == tmp_reg || si->dst_reg == tmp_reg) \ @@ -7751,8 +7758,7 @@ static u32 xdp_convert_ctx_access(enum bpf_access_type type, offsetof(S, TF)); \ *insn++ = BPF_LDX_MEM(BPF_FIELD_SIZEOF(S, F), tmp_reg, \ si->dst_reg, offsetof(S, F)); \ - *insn++ = BPF_STX_MEM( \ - BPF_FIELD_SIZEOF(NS, NF), tmp_reg, si->src_reg, \ + *insn++ = BPF_STX_MEM(SIZE, tmp_reg, si->src_reg, \ bpf_target_off(NS, NF, FIELD_SIZEOF(NS, NF), \ target_size) \ + OFF); \ @@ -7764,8 +7770,8 @@ static u32 xdp_convert_ctx_access(enum bpf_access_type type, TF) \ do { \ if (type == BPF_WRITE) { \ - SOCK_ADDR_STORE_NESTED_FIELD_OFF(S, NS, F, NF, OFF, \ - TF); \ + SOCK_ADDR_STORE_NESTED_FIELD_OFF(S, NS, F, NF, SIZE, \ + OFF, TF); \ } else { \ SOCK_ADDR_LOAD_NESTED_FIELD_SIZE_OFF( \ S, NS, F, NF, SIZE, OFF); \ From 4cfacbe6df972db4081dd76feb7871fce996118d Mon Sep 17 00:00:00 2001 From: Stanislav Fomichev Date: Mon, 1 Jul 2019 10:38:40 -0700 Subject: [PATCH 2/3] bpf: sync bpf.h to tools/ Sync user_ip6 & msg_src_ip6 comments. Signed-off-by: Stanislav Fomichev Signed-off-by: Daniel Borkmann --- tools/include/uapi/linux/bpf.h | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) diff --git a/tools/include/uapi/linux/bpf.h b/tools/include/uapi/linux/bpf.h index cecf42c871d4..e692bb21846f 100644 --- a/tools/include/uapi/linux/bpf.h +++ b/tools/include/uapi/linux/bpf.h @@ -3244,7 +3244,7 @@ struct bpf_sock_addr { __u32 user_ip4; /* Allows 1,2,4-byte read and 4-byte write. * Stored in network byte order. */ - __u32 user_ip6[4]; /* Allows 1,2,4-byte read an 4-byte write. + __u32 user_ip6[4]; /* Allows 1,2,4-byte read and 4,8-byte write. * Stored in network byte order. */ __u32 user_port; /* Allows 4-byte read and write. @@ -3253,10 +3253,10 @@ struct bpf_sock_addr { __u32 family; /* Allows 4-byte read, but no write */ __u32 type; /* Allows 4-byte read, but no write */ __u32 protocol; /* Allows 4-byte read, but no write */ - __u32 msg_src_ip4; /* Allows 1,2,4-byte read an 4-byte write. + __u32 msg_src_ip4; /* Allows 1,2,4-byte read and 4-byte write. * Stored in network byte order. */ - __u32 msg_src_ip6[4]; /* Allows 1,2,4-byte read an 4-byte write. + __u32 msg_src_ip6[4]; /* Allows 1,2,4-byte read and 4,8-byte write. * Stored in network byte order. */ __bpf_md_ptr(struct bpf_sock *, sk); From 76d950773cd2a365f492ce973429ae629d58131c Mon Sep 17 00:00:00 2001 From: Stanislav Fomichev Date: Mon, 1 Jul 2019 10:38:41 -0700 Subject: [PATCH 3/3] selftests/bpf: add verifier tests for wide stores Make sure that wide stores are allowed at proper (aligned) addresses. Note that user_ip6 is naturally aligned on 8-byte boundary, so correct addresses are user_ip6[0] and user_ip6[2]. msg_src_ip6 is, however, aligned on a 4-byte bondary, so only msg_src_ip6[1] can be wide-stored. Cc: Andrii Nakryiko Cc: Yonghong Song Acked-by: Andrii Nakryiko Signed-off-by: Stanislav Fomichev Acked-by: Yonghong Song Signed-off-by: Daniel Borkmann --- tools/testing/selftests/bpf/test_verifier.c | 17 +++++++-- .../selftests/bpf/verifier/wide_store.c | 36 +++++++++++++++++++ 2 files changed, 50 insertions(+), 3 deletions(-) create mode 100644 tools/testing/selftests/bpf/verifier/wide_store.c diff --git a/tools/testing/selftests/bpf/test_verifier.c b/tools/testing/selftests/bpf/test_verifier.c index c5514daf8865..b0773291012a 100644 --- a/tools/testing/selftests/bpf/test_verifier.c +++ b/tools/testing/selftests/bpf/test_verifier.c @@ -105,6 +105,7 @@ struct bpf_test { __u64 data64[TEST_DATA_LEN / 8]; }; } retvals[MAX_TEST_RUNS]; + enum bpf_attach_type expected_attach_type; }; /* Note we want this to be 64 bit aligned so that the end of our array is @@ -850,6 +851,7 @@ static void do_test_single(struct bpf_test *test, bool unpriv, int fd_prog, expected_ret, alignment_prevented_execution; int prog_len, prog_type = test->prog_type; struct bpf_insn *prog = test->insns; + struct bpf_load_program_attr attr; int run_errs, run_successes; int map_fds[MAX_NR_MAPS]; const char *expected_err; @@ -881,8 +883,17 @@ static void do_test_single(struct bpf_test *test, bool unpriv, pflags |= BPF_F_STRICT_ALIGNMENT; if (test->flags & F_NEEDS_EFFICIENT_UNALIGNED_ACCESS) pflags |= BPF_F_ANY_ALIGNMENT; - fd_prog = bpf_verify_program(prog_type, prog, prog_len, pflags, - "GPL", 0, bpf_vlog, sizeof(bpf_vlog), 4); + + memset(&attr, 0, sizeof(attr)); + attr.prog_type = prog_type; + attr.expected_attach_type = test->expected_attach_type; + attr.insns = prog; + attr.insns_cnt = prog_len; + attr.license = "GPL"; + attr.log_level = 4; + attr.prog_flags = pflags; + + fd_prog = bpf_load_program_xattr(&attr, bpf_vlog, sizeof(bpf_vlog)); if (fd_prog < 0 && !bpf_probe_prog_type(prog_type, 0)) { printf("SKIP (unsupported program type %d)\n", prog_type); skips++; @@ -912,7 +923,7 @@ static void do_test_single(struct bpf_test *test, bool unpriv, printf("FAIL\nUnexpected success to load!\n"); goto fail_log; } - if (!strstr(bpf_vlog, expected_err)) { + if (!expected_err || !strstr(bpf_vlog, expected_err)) { printf("FAIL\nUnexpected error message!\n\tEXP: %s\n\tRES: %s\n", expected_err, bpf_vlog); goto fail_log; diff --git a/tools/testing/selftests/bpf/verifier/wide_store.c b/tools/testing/selftests/bpf/verifier/wide_store.c new file mode 100644 index 000000000000..8fe99602ded4 --- /dev/null +++ b/tools/testing/selftests/bpf/verifier/wide_store.c @@ -0,0 +1,36 @@ +#define BPF_SOCK_ADDR(field, off, res, err) \ +{ \ + "wide store to bpf_sock_addr." #field "[" #off "]", \ + .insns = { \ + BPF_MOV64_IMM(BPF_REG_0, 1), \ + BPF_STX_MEM(BPF_DW, BPF_REG_1, BPF_REG_0, \ + offsetof(struct bpf_sock_addr, field[off])), \ + BPF_EXIT_INSN(), \ + }, \ + .result = res, \ + .prog_type = BPF_PROG_TYPE_CGROUP_SOCK_ADDR, \ + .expected_attach_type = BPF_CGROUP_UDP6_SENDMSG, \ + .errstr = err, \ +} + +/* user_ip6[0] is u64 aligned */ +BPF_SOCK_ADDR(user_ip6, 0, ACCEPT, + NULL), +BPF_SOCK_ADDR(user_ip6, 1, REJECT, + "invalid bpf_context access off=12 size=8"), +BPF_SOCK_ADDR(user_ip6, 2, ACCEPT, + NULL), +BPF_SOCK_ADDR(user_ip6, 3, REJECT, + "invalid bpf_context access off=20 size=8"), + +/* msg_src_ip6[0] is _not_ u64 aligned */ +BPF_SOCK_ADDR(msg_src_ip6, 0, REJECT, + "invalid bpf_context access off=44 size=8"), +BPF_SOCK_ADDR(msg_src_ip6, 1, ACCEPT, + NULL), +BPF_SOCK_ADDR(msg_src_ip6, 2, REJECT, + "invalid bpf_context access off=52 size=8"), +BPF_SOCK_ADDR(msg_src_ip6, 3, REJECT, + "invalid bpf_context access off=56 size=8"), + +#undef BPF_SOCK_ADDR