| Message ID | 20220708175000.2603078-1-sdf@google.com (mailing list archive) |
|---|---|
| State | Accepted |
| Commit | d1a6edecc1fddfb6ef92c8f720631d2c02bf2744 |
| Delegated to: | BPF |
| Headers | show |
| Series | [bpf-next,v3] bpf: check attach_func_proto more carefully in check_return_code | expand |
On Fri, Jul 08, 2022 at 10:50:00AM -0700, Stanislav Fomichev wrote: > Syzkaller reports the following crash: > RIP: 0010:check_return_code kernel/bpf/verifier.c:10575 [inline] > RIP: 0010:do_check kernel/bpf/verifier.c:12346 [inline] > RIP: 0010:do_check_common+0xb3d2/0xd250 kernel/bpf/verifier.c:14610 > > With the following reproducer: > bpf$PROG_LOAD_XDP(0x5, &(0x7f00000004c0)={0xd, 0x3, &(0x7f0000000000)=ANY=[@ANYBLOB="1800000000000019000000000000000095"], &(0x7f0000000300)='GPL\x00', 0x0, 0x0, 0x0, 0x0, 0x0, '\x00', 0x0, 0x2b, 0xffffffffffffffff, 0x8, 0x0, 0x0, 0x10, 0x0}, 0x80) > > Because we don't enforce expected_attach_type for XDP programs, > we end up in hitting 'if (prog->expected_attach_type == BPF_LSM_CGROUP' > part in check_return_code and follow up with testing > `prog->aux->attach_func_proto->type`, but `prog->aux->attach_func_proto` > is NULL. > > Add explicit prog_type check for the "Note, BPF_LSM_CGROUP that > attach ..." condition. Also, don't skip return code check for > LSM/STRUCT_OPS. > > The above actually brings an issue with existing selftest which > tries to return EPERM from void inet_csk_clone. Fix the > test (and move called_socket_clone to make sure it's not > incremented in case of an error) and add a new one to explicitly > verify this condition. Acked-by: Martin KaFai Lau <kafai@fb.com>
Hello: This patch was applied to bpf/bpf-next.git (master) by Daniel Borkmann <daniel@iogearbox.net>: On Fri, 8 Jul 2022 10:50:00 -0700 you wrote: > Syzkaller reports the following crash: > RIP: 0010:check_return_code kernel/bpf/verifier.c:10575 [inline] > RIP: 0010:do_check kernel/bpf/verifier.c:12346 [inline] > RIP: 0010:do_check_common+0xb3d2/0xd250 kernel/bpf/verifier.c:14610 > > With the following reproducer: > bpf$PROG_LOAD_XDP(0x5, &(0x7f00000004c0)={0xd, 0x3, &(0x7f0000000000)=ANY=[@ANYBLOB="1800000000000019000000000000000095"], &(0x7f0000000300)='GPL\x00', 0x0, 0x0, 0x0, 0x0, 0x0, '\x00', 0x0, 0x2b, 0xffffffffffffffff, 0x8, 0x0, 0x0, 0x10, 0x0}, 0x80) > > [...] Here is the summary with links: - [bpf-next,v3] bpf: check attach_func_proto more carefully in check_return_code https://git.kernel.org/bpf/bpf-next/c/d1a6edecc1fd You are awesome, thank you!
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c index df3ec6b05f05..e3cf6194c24f 100644 --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -10444,11 +10444,21 @@ static int check_return_code(struct bpf_verifier_env *env) const bool is_subprog = frame->subprogno; /* LSM and struct_ops func-ptr's return type could be "void" */ - if (!is_subprog && - (prog_type == BPF_PROG_TYPE_STRUCT_OPS || - prog_type == BPF_PROG_TYPE_LSM) && - !prog->aux->attach_func_proto->type) - return 0; + if (!is_subprog) { + switch (prog_type) { + case BPF_PROG_TYPE_LSM: + if (prog->expected_attach_type == BPF_LSM_CGROUP) + /* See below, can be 0 or 0-1 depending on hook. */ + break; + fallthrough; + case BPF_PROG_TYPE_STRUCT_OPS: + if (!prog->aux->attach_func_proto->type) + return 0; + break; + default: + break; + } + } /* eBPF calling convention is such that R0 is used * to return the value from eBPF program. @@ -10572,6 +10582,7 @@ static int check_return_code(struct bpf_verifier_env *env) if (!tnum_in(range, reg->var_off)) { verbose_invalid_scalar(env, reg, &range, "program exit", "R0"); if (prog->expected_attach_type == BPF_LSM_CGROUP && + prog_type == BPF_PROG_TYPE_LSM && !prog->aux->attach_func_proto->type) verbose(env, "Note, BPF_LSM_CGROUP that attach to void LSM hooks can't modify return value!\n"); return -EINVAL; diff --git a/tools/testing/selftests/bpf/prog_tests/lsm_cgroup.c b/tools/testing/selftests/bpf/prog_tests/lsm_cgroup.c index c542d7e80a5b..1102e4f42d2d 100644 --- a/tools/testing/selftests/bpf/prog_tests/lsm_cgroup.c +++ b/tools/testing/selftests/bpf/prog_tests/lsm_cgroup.c @@ -6,6 +6,7 @@ #include <bpf/btf.h> #include "lsm_cgroup.skel.h" +#include "lsm_cgroup_nonvoid.skel.h" #include "cgroup_helpers.h" #include "network_helpers.h" @@ -293,9 +294,20 @@ static void test_lsm_cgroup_functional(void) lsm_cgroup__destroy(skel); } +static void test_lsm_cgroup_nonvoid(void) +{ + struct lsm_cgroup_nonvoid *skel = NULL; + + skel = lsm_cgroup_nonvoid__open_and_load(); + ASSERT_NULL(skel, "open succeeds"); + lsm_cgroup_nonvoid__destroy(skel); +} + void test_lsm_cgroup(void) { if (test__start_subtest("functional")) test_lsm_cgroup_functional(); + if (test__start_subtest("nonvoid")) + test_lsm_cgroup_nonvoid(); btf__free(btf); } diff --git a/tools/testing/selftests/bpf/progs/lsm_cgroup.c b/tools/testing/selftests/bpf/progs/lsm_cgroup.c index 89f3b1e961a8..4f2d60b87b75 100644 --- a/tools/testing/selftests/bpf/progs/lsm_cgroup.c +++ b/tools/testing/selftests/bpf/progs/lsm_cgroup.c @@ -156,25 +156,25 @@ int BPF_PROG(socket_clone, struct sock *newsk, const struct request_sock *req) { int prio = 234; - called_socket_clone++; - if (!newsk) return 1; /* Accepted request sockets get a different priority. */ if (bpf_setsockopt(newsk, SOL_SOCKET, SO_PRIORITY, &prio, sizeof(prio))) - return 0; /* EPERM */ + return 1; /* Make sure bpf_getsockopt is allowed and works. */ prio = 0; if (bpf_getsockopt(newsk, SOL_SOCKET, SO_PRIORITY, &prio, sizeof(prio))) - return 0; /* EPERM */ + return 1; if (prio != 234) - return 0; /* EPERM */ + return 1; /* Can access cgroup local storage. */ if (!test_local_storage()) - return 0; /* EPERM */ + return 1; + + called_socket_clone++; return 1; } diff --git a/tools/testing/selftests/bpf/progs/lsm_cgroup_nonvoid.c b/tools/testing/selftests/bpf/progs/lsm_cgroup_nonvoid.c new file mode 100644 index 000000000000..6cb0f161f417 --- /dev/null +++ b/tools/testing/selftests/bpf/progs/lsm_cgroup_nonvoid.c @@ -0,0 +1,14 @@ +// SPDX-License-Identifier: GPL-2.0 + +#include "vmlinux.h" +#include <bpf/bpf_helpers.h> +#include <bpf/bpf_tracing.h> + +char _license[] SEC("license") = "GPL"; + +SEC("lsm_cgroup/inet_csk_clone") +int BPF_PROG(nonvoid_socket_clone, struct sock *newsk, const struct request_sock *req) +{ + /* Can not return any errors from void LSM hooks. */ + return 0; +}
Syzkaller reports the following crash: RIP: 0010:check_return_code kernel/bpf/verifier.c:10575 [inline] RIP: 0010:do_check kernel/bpf/verifier.c:12346 [inline] RIP: 0010:do_check_common+0xb3d2/0xd250 kernel/bpf/verifier.c:14610 With the following reproducer: bpf$PROG_LOAD_XDP(0x5, &(0x7f00000004c0)={0xd, 0x3, &(0x7f0000000000)=ANY=[@ANYBLOB="1800000000000019000000000000000095"], &(0x7f0000000300)='GPL\x00', 0x0, 0x0, 0x0, 0x0, 0x0, '\x00', 0x0, 0x2b, 0xffffffffffffffff, 0x8, 0x0, 0x0, 0x10, 0x0}, 0x80) Because we don't enforce expected_attach_type for XDP programs, we end up in hitting 'if (prog->expected_attach_type == BPF_LSM_CGROUP' part in check_return_code and follow up with testing `prog->aux->attach_func_proto->type`, but `prog->aux->attach_func_proto` is NULL. Add explicit prog_type check for the "Note, BPF_LSM_CGROUP that attach ..." condition. Also, don't skip return code check for LSM/STRUCT_OPS. The above actually brings an issue with existing selftest which tries to return EPERM from void inet_csk_clone. Fix the test (and move called_socket_clone to make sure it's not incremented in case of an error) and add a new one to explicitly verify this condition. v3: - Martin: handle expected_attach_type for BPF_PROG_TYPE_STRUCT_OPS as well v2: - Martin: don't add new helper, check prog_type instead - Martin: check expected_attach_type as well at the function entry - Update selftest to verify this condition Fixes: 69fd337a975c ("bpf: per-cgroup lsm flavor") Reported-by: syzbot+5cc0730bd4b4d2c5f152@syzkaller.appspotmail.com Signed-off-by: Stanislav Fomichev <sdf@google.com> --- kernel/bpf/verifier.c | 21 ++++++++++++++----- .../selftests/bpf/prog_tests/lsm_cgroup.c | 12 +++++++++++ .../testing/selftests/bpf/progs/lsm_cgroup.c | 12 +++++------ .../selftests/bpf/progs/lsm_cgroup_nonvoid.c | 14 +++++++++++++ 4 files changed, 48 insertions(+), 11 deletions(-) create mode 100644 tools/testing/selftests/bpf/progs/lsm_cgroup_nonvoid.c