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.
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@xxxxxxxxxxxxxxxxxxxxxxxxx
Signed-off-by: Stanislav Fomichev <sdf@xxxxxxxxxx>
---
kernel/bpf/verifier.c | 2 ++
.../testing/selftests/bpf/prog_tests/lsm_cgroup.c | 12 ++++++++++++
tools/testing/selftests/bpf/progs/lsm_cgroup.c | 12 ++++++------
.../selftests/bpf/progs/lsm_cgroup_nonvoid.c | 14 ++++++++++++++
4 files changed, 34 insertions(+), 6 deletions(-)
create mode 100644 tools/testing/selftests/bpf/progs/lsm_cgroup_nonvoid.c
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index df3ec6b05f05..2bc1e7252778 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -10445,6 +10445,7 @@ static int check_return_code(struct bpf_verifier_env *env)
/* LSM and struct_ops func-ptr's return type could be "void" */
if (!is_subprog &&
+ prog->expected_attach_type != BPF_LSM_CGROUP &&
(prog_type == BPF_PROG_TYPE_STRUCT_OPS ||
prog_type == BPF_PROG_TYPE_LSM) &&
!prog->aux->attach_func_proto->type)
@@ -10572,6 +10573,7 @@ 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;
+}
--
2.37.0.rc0.161.g10f37bed90-goog
