diff --git a/include/linux/bpf_lsm.h b/include/linux/bpf_lsm.h index 643809cc78c3..143775a27a2a 100644 --- a/include/linux/bpf_lsm.h +++ b/include/linux/bpf_lsm.h @@ -52,6 +52,7 @@ int bpf_set_dentry_xattr_locked(struct dentry *dentry, const char *name__str, const struct bpf_dynptr *value_p, int flags); int bpf_remove_dentry_xattr_locked(struct dentry *dentry, const char *name__str); bool bpf_lsm_has_d_inode_locked(const struct bpf_prog *prog); +bool bpf_lsm_hook_returns_errno(u32 btf_id); #else /* !CONFIG_BPF_LSM */ @@ -104,6 +105,11 @@ static inline bool bpf_lsm_has_d_inode_locked(const struct bpf_prog *prog) { return false; } + +static inline bool bpf_lsm_hook_returns_errno(u32 btf_id) +{ + return true; +} #endif /* CONFIG_BPF_LSM */ #endif /* _LINUX_BPF_LSM_H */ diff --git a/kernel/bpf/bpf_lsm.c b/kernel/bpf/bpf_lsm.c index c5c925f00202..564071a92d7d 100644 --- a/kernel/bpf/bpf_lsm.c +++ b/kernel/bpf/bpf_lsm.c @@ -427,6 +427,26 @@ BTF_ID(func, bpf_lsm_audit_rule_known) BTF_ID(func, bpf_lsm_inode_xattr_skipcap) BTF_SET_END(bool_lsm_hooks) +/* hooks returning void */ +#define LSM_HOOK_void(DEFAULT, NAME, ...) BTF_ID(func, bpf_lsm_##NAME) +#define LSM_HOOK_int(DEFAULT, NAME, ...) /* nothing */ +#define LSM_HOOK(RET, DEFAULT, NAME, ...) LSM_HOOK_##RET(DEFAULT, NAME, __VA_ARGS__) +BTF_SET_START(void_lsm_hooks) +#include +#undef LSM_HOOK +#undef LSM_HOOK_void +#undef LSM_HOOK_int +BTF_SET_END(void_lsm_hooks) + +bool bpf_lsm_hook_returns_errno(u32 btf_id) +{ + if (btf_id_set_contains(&bool_lsm_hooks, btf_id)) + return false; + if (btf_id_set_contains(&void_lsm_hooks, btf_id)) + return false; + return true; +} + int bpf_lsm_get_retval_range(const struct bpf_prog *prog, struct bpf_retval_range *retval_range) { diff --git a/kernel/bpf/cgroup.c b/kernel/bpf/cgroup.c index 35d1f1428ef3..83ce66296ac1 100644 --- a/kernel/bpf/cgroup.c +++ b/kernel/bpf/cgroup.c @@ -55,6 +55,28 @@ void __init cgroup_bpf_lifetime_notifier_init(void) &cgroup_bpf_lifetime_nb)); } +#ifdef CONFIG_BPF_LSM +struct cgroup_lsm_atype { + u32 attach_btf_id; + int refcnt; + bool returns_errno; +}; + +static struct cgroup_lsm_atype cgroup_lsm_atype[CGROUP_LSM_NUM]; + +static bool cgroup_bpf_hook_returns_errno(enum cgroup_bpf_attach_type atype) +{ + if (atype >= CGROUP_LSM_START && atype <= CGROUP_LSM_END) + return READ_ONCE(cgroup_lsm_atype[atype - CGROUP_LSM_START].returns_errno); + return true; +} +#else +static bool cgroup_bpf_hook_returns_errno(enum cgroup_bpf_attach_type atype) +{ + return true; +} +#endif + /* __always_inline is necessary to prevent indirect call through run_prog * function pointer. */ @@ -83,7 +105,8 @@ bpf_prog_run_array_cg(const struct cgroup_bpf *cgrp, *(ret_flags) |= (func_ret >> 1); func_ret &= 1; } - if (!func_ret && !IS_ERR_VALUE((long)run_ctx.retval)) + if (!func_ret && cgroup_bpf_hook_returns_errno(atype) && + !IS_ERR_VALUE((long)run_ctx.retval)) run_ctx.retval = -EPERM; item++; } @@ -156,13 +179,6 @@ unsigned int __cgroup_bpf_run_lsm_current(const void *ctx, } #ifdef CONFIG_BPF_LSM -struct cgroup_lsm_atype { - u32 attach_btf_id; - int refcnt; -}; - -static struct cgroup_lsm_atype cgroup_lsm_atype[CGROUP_LSM_NUM]; - static enum cgroup_bpf_attach_type bpf_cgroup_atype_find(enum bpf_attach_type attach_type, u32 attach_btf_id) { @@ -191,10 +207,13 @@ void bpf_cgroup_atype_get(u32 attach_btf_id, int cgroup_atype) lockdep_assert_held(&cgroup_mutex); - WARN_ON_ONCE(cgroup_lsm_atype[i].attach_btf_id && - cgroup_lsm_atype[i].attach_btf_id != attach_btf_id); - - cgroup_lsm_atype[i].attach_btf_id = attach_btf_id; + if (!cgroup_lsm_atype[i].attach_btf_id) { + cgroup_lsm_atype[i].attach_btf_id = attach_btf_id; + WRITE_ONCE(cgroup_lsm_atype[i].returns_errno, + bpf_lsm_hook_returns_errno(attach_btf_id)); + } else { + WARN_ON_ONCE(cgroup_lsm_atype[i].attach_btf_id != attach_btf_id); + } cgroup_lsm_atype[i].refcnt++; } @@ -203,8 +222,10 @@ void bpf_cgroup_atype_put(int cgroup_atype) int i = cgroup_atype - CGROUP_LSM_START; cgroup_lock(); - if (--cgroup_lsm_atype[i].refcnt <= 0) + if (--cgroup_lsm_atype[i].refcnt <= 0) { + WRITE_ONCE(cgroup_lsm_atype[i].returns_errno, true); cgroup_lsm_atype[i].attach_btf_id = 0; + } WARN_ON_ONCE(cgroup_lsm_atype[i].refcnt < 0); cgroup_unlock(); } diff --git a/tools/testing/selftests/bpf/prog_tests/lsm_cgroup.c b/tools/testing/selftests/bpf/prog_tests/lsm_cgroup.c index 6df25de8f080..41e867467f6c 100644 --- a/tools/testing/selftests/bpf/prog_tests/lsm_cgroup.c +++ b/tools/testing/selftests/bpf/prog_tests/lsm_cgroup.c @@ -2,6 +2,7 @@ #include #include +#include #include #include @@ -309,11 +310,89 @@ static void test_lsm_cgroup_nonvoid(void) lsm_cgroup_nonvoid__destroy(skel); } +static void test_lsm_cgroup_retval(void) +{ + struct lsm_cgroup *skel = NULL; + int skipcap_prog_fd1, skipcap_prog_fd2, socket_prog_fd1, socket_prog_fd2; + int cgroup_fd = -1; + int err, fd; + char tmpfile[] = "/tmp/test_lsm_cgroup_retval.XXXXXX"; + + fd = mkstemp(tmpfile); + if (!ASSERT_OK_FD(fd, "mkstemp")) + return; + close(fd); + + cgroup_fd = test__join_cgroup("/default_retval"); + if (!ASSERT_OK_FD(cgroup_fd, "join_cgroup")) + goto cleanup_tmpfile; + + skel = lsm_cgroup__open_and_load(); + if (!ASSERT_OK_PTR(skel, "open_and_load")) + goto cleanup_cgroup; + + skipcap_prog_fd1 = bpf_program__fd(skel->progs.skipcap_first); + skipcap_prog_fd2 = bpf_program__fd(skel->progs.skipcap_second); + socket_prog_fd1 = bpf_program__fd(skel->progs.socket_first); + socket_prog_fd2 = bpf_program__fd(skel->progs.socket_second); + + err = bpf_prog_attach(skipcap_prog_fd1, cgroup_fd, BPF_LSM_CGROUP, BPF_F_ALLOW_MULTI); + if (err == -ENOTSUPP) { + test__skip(); + goto cleanup_skeleton; + } + if (!ASSERT_OK(err, "attach first skipcap prog")) + goto cleanup_skeleton; + + err = bpf_prog_attach(skipcap_prog_fd2, cgroup_fd, BPF_LSM_CGROUP, BPF_F_ALLOW_MULTI); + if (!ASSERT_OK(err, "attach second skipcap prog")) + goto cleanup_skipcap1; + + err = bpf_prog_attach(socket_prog_fd1, cgroup_fd, BPF_LSM_CGROUP, BPF_F_ALLOW_MULTI); + if (!ASSERT_OK(err, "attach first sock_create prog")) + goto cleanup_skipcap2; + + err = bpf_prog_attach(socket_prog_fd2, cgroup_fd, BPF_LSM_CGROUP, BPF_F_ALLOW_MULTI); + if (!ASSERT_OK(err, "attach second sock_create prog")) + goto cleanup_sock_create1; + + /* trigger the bool hook by setxattr */ + err = setxattr(tmpfile, "user.test", "value", 5, 0); + if (!ASSERT_OK(err, "setxattr")) + goto cleanup_sock_create2; + + /* trigger the errno hook by creating a socket */ + fd = socket(AF_INET, SOCK_STREAM, 0); + if (!ASSERT_OK_FD(fd, "socket")) + goto cleanup_sock_create2; + close(fd); + + ASSERT_EQ(skel->data->skipcap_retval, 0, "bool_hook_retval_should_be_0"); + ASSERT_EQ(skel->data->socket_retval, -EPERM, "errno_hook_retval_should_be_EPERM"); + +cleanup_sock_create2: + bpf_prog_detach2(socket_prog_fd2, cgroup_fd, BPF_LSM_CGROUP); +cleanup_sock_create1: + bpf_prog_detach2(socket_prog_fd1, cgroup_fd, BPF_LSM_CGROUP); +cleanup_skipcap2: + bpf_prog_detach2(skipcap_prog_fd2, cgroup_fd, BPF_LSM_CGROUP); +cleanup_skipcap1: + bpf_prog_detach2(skipcap_prog_fd1, cgroup_fd, BPF_LSM_CGROUP); +cleanup_skeleton: + lsm_cgroup__destroy(skel); +cleanup_cgroup: + close(cgroup_fd); +cleanup_tmpfile: + unlink(tmpfile); +} + void test_lsm_cgroup(void) { if (test__start_subtest("functional")) test_lsm_cgroup_functional(); if (test__start_subtest("nonvoid")) test_lsm_cgroup_nonvoid(); + if (test__start_subtest("retval")) + test_lsm_cgroup_retval(); btf__free(btf); } diff --git a/tools/testing/selftests/bpf/progs/lsm_cgroup.c b/tools/testing/selftests/bpf/progs/lsm_cgroup.c index d7598538aa2d..3bfa479104be 100644 --- a/tools/testing/selftests/bpf/progs/lsm_cgroup.c +++ b/tools/testing/selftests/bpf/progs/lsm_cgroup.c @@ -35,6 +35,8 @@ int called_socket_bind; int called_socket_bind2; int called_socket_alloc; int called_socket_clone; +int skipcap_retval = -4095; +int socket_retval = -4095; static __always_inline int test_local_storage(void) { @@ -190,3 +192,31 @@ int BPF_PROG(socket_clone, struct sock *newsk, const struct request_sock *req) return 1; } + +SEC("lsm_cgroup/inode_xattr_skipcap") +int BPF_PROG(skipcap_first, const char *name) +{ + return 0; +} + +SEC("lsm_cgroup/inode_xattr_skipcap") +int BPF_PROG(skipcap_second, const char *name) +{ + skipcap_retval = bpf_get_retval(); + bpf_set_retval(0); + return 1; +} + +SEC("lsm_cgroup/socket_create") +int BPF_PROG(socket_first, int family, int type, int protocol, int kern) +{ + return 0; +} + +SEC("lsm_cgroup/socket_create") +int BPF_PROG(socket_second, int family, int type, int protocol, int kern) +{ + socket_retval = bpf_get_retval(); + bpf_set_retval(0); + return 1; +}