From 1d71283987c729dceccce834a864c27301ba155e Mon Sep 17 00:00:00 2001 From: David Vernet Date: Mon, 10 Apr 2023 23:16:31 -0500 Subject: [PATCH] bpf: Make bpf_cgroup_acquire() KF_RCU | KF_RET_NULL struct cgroup is already an RCU-safe type in the verifier. We can therefore update bpf_cgroup_acquire() to be KF_RCU | KF_RET_NULL, and subsequently remove bpf_cgroup_kptr_get(). This patch does the first of these by updating bpf_cgroup_acquire() to be KF_RCU | KF_RET_NULL, and also updates selftests accordingly. Signed-off-by: David Vernet Link: https://lore.kernel.org/r/20230411041633.179404-1-void@manifault.com Signed-off-by: Alexei Starovoitov --- kernel/bpf/helpers.c | 5 ++-- .../selftests/bpf/progs/cgrp_kfunc_common.h | 5 ++++ .../selftests/bpf/progs/cgrp_kfunc_failure.c | 35 ++++++++++++++++++---- .../selftests/bpf/progs/cgrp_kfunc_success.c | 5 +++- 4 files changed, 40 insertions(+), 10 deletions(-) diff --git a/kernel/bpf/helpers.c b/kernel/bpf/helpers.c index b6a5cda..71f0604 100644 --- a/kernel/bpf/helpers.c +++ b/kernel/bpf/helpers.c @@ -2037,8 +2037,7 @@ __bpf_kfunc void bpf_task_release(struct task_struct *p) */ __bpf_kfunc struct cgroup *bpf_cgroup_acquire(struct cgroup *cgrp) { - cgroup_get(cgrp); - return cgrp; + return cgroup_tryget(cgrp) ? cgrp : NULL; } /** @@ -2314,7 +2313,7 @@ BTF_ID_FLAGS(func, bpf_rbtree_add) BTF_ID_FLAGS(func, bpf_rbtree_first, KF_RET_NULL) #ifdef CONFIG_CGROUPS -BTF_ID_FLAGS(func, bpf_cgroup_acquire, KF_ACQUIRE | KF_TRUSTED_ARGS) +BTF_ID_FLAGS(func, bpf_cgroup_acquire, KF_ACQUIRE | KF_RCU | KF_RET_NULL) BTF_ID_FLAGS(func, bpf_cgroup_kptr_get, KF_ACQUIRE | KF_KPTR_GET | KF_RET_NULL) BTF_ID_FLAGS(func, bpf_cgroup_release, KF_RELEASE) BTF_ID_FLAGS(func, bpf_cgroup_ancestor, KF_ACQUIRE | KF_RCU | KF_RET_NULL) diff --git a/tools/testing/selftests/bpf/progs/cgrp_kfunc_common.h b/tools/testing/selftests/bpf/progs/cgrp_kfunc_common.h index d0b7cd0..b0e279f 100644 --- a/tools/testing/selftests/bpf/progs/cgrp_kfunc_common.h +++ b/tools/testing/selftests/bpf/progs/cgrp_kfunc_common.h @@ -61,6 +61,11 @@ static inline int cgrps_kfunc_map_insert(struct cgroup *cgrp) } acquired = bpf_cgroup_acquire(cgrp); + if (!acquired) { + bpf_map_delete_elem(&__cgrps_kfunc_map, &id); + return -ENOENT; + } + old = bpf_kptr_xchg(&v->cgrp, acquired); if (old) { bpf_cgroup_release(old); diff --git a/tools/testing/selftests/bpf/progs/cgrp_kfunc_failure.c b/tools/testing/selftests/bpf/progs/cgrp_kfunc_failure.c index 48b2034..49347f1 100644 --- a/tools/testing/selftests/bpf/progs/cgrp_kfunc_failure.c +++ b/tools/testing/selftests/bpf/progs/cgrp_kfunc_failure.c @@ -41,6 +41,23 @@ int BPF_PROG(cgrp_kfunc_acquire_untrusted, struct cgroup *cgrp, const char *path /* Can't invoke bpf_cgroup_acquire() on an untrusted pointer. */ acquired = bpf_cgroup_acquire(v->cgrp); + if (acquired) + bpf_cgroup_release(acquired); + + return 0; +} + +SEC("tp_btf/cgroup_mkdir") +__failure __msg("Possibly NULL pointer passed to trusted arg0") +int BPF_PROG(cgrp_kfunc_acquire_no_null_check, struct cgroup *cgrp, const char *path) +{ + struct cgroup *acquired; + + acquired = bpf_cgroup_acquire(cgrp); + /* + * Can't invoke bpf_cgroup_release() without checking the return value + * of bpf_cgroup_acquire(). + */ bpf_cgroup_release(acquired); return 0; @@ -54,7 +71,8 @@ int BPF_PROG(cgrp_kfunc_acquire_fp, struct cgroup *cgrp, const char *path) /* Can't invoke bpf_cgroup_acquire() on a random frame pointer. */ acquired = bpf_cgroup_acquire((struct cgroup *)&stack_cgrp); - bpf_cgroup_release(acquired); + if (acquired) + bpf_cgroup_release(acquired); return 0; } @@ -67,7 +85,8 @@ int BPF_PROG(cgrp_kfunc_acquire_unsafe_kretprobe, struct cgroup *cgrp) /* Can't acquire an untrusted struct cgroup * pointer. */ acquired = bpf_cgroup_acquire(cgrp); - bpf_cgroup_release(acquired); + if (acquired) + bpf_cgroup_release(acquired); return 0; } @@ -80,7 +99,8 @@ int BPF_PROG(cgrp_kfunc_acquire_trusted_walked, struct cgroup *cgrp, const char /* Can't invoke bpf_cgroup_acquire() on a pointer obtained from walking a trusted cgroup. */ acquired = bpf_cgroup_acquire(cgrp->old_dom_cgrp); - bpf_cgroup_release(acquired); + if (acquired) + bpf_cgroup_release(acquired); return 0; } @@ -93,9 +113,8 @@ int BPF_PROG(cgrp_kfunc_acquire_null, struct cgroup *cgrp, const char *path) /* Can't invoke bpf_cgroup_acquire() on a NULL pointer. */ acquired = bpf_cgroup_acquire(NULL); - if (!acquired) - return 0; - bpf_cgroup_release(acquired); + if (acquired) + bpf_cgroup_release(acquired); return 0; } @@ -137,6 +156,8 @@ int BPF_PROG(cgrp_kfunc_get_non_kptr_acquired, struct cgroup *cgrp, const char * struct cgroup *kptr, *acquired; acquired = bpf_cgroup_acquire(cgrp); + if (!acquired) + return 0; /* Cannot use bpf_cgroup_kptr_get() on a non-map-value, even if the kptr was acquired. */ kptr = bpf_cgroup_kptr_get(&acquired); @@ -256,6 +277,8 @@ int BPF_PROG(cgrp_kfunc_release_null, struct cgroup *cgrp, const char *path) return -ENOENT; acquired = bpf_cgroup_acquire(cgrp); + if (!acquired) + return -ENOENT; old = bpf_kptr_xchg(&v->cgrp, acquired); diff --git a/tools/testing/selftests/bpf/progs/cgrp_kfunc_success.c b/tools/testing/selftests/bpf/progs/cgrp_kfunc_success.c index 030aff7..e9dbd1a 100644 --- a/tools/testing/selftests/bpf/progs/cgrp_kfunc_success.c +++ b/tools/testing/selftests/bpf/progs/cgrp_kfunc_success.c @@ -38,7 +38,10 @@ int BPF_PROG(test_cgrp_acquire_release_argument, struct cgroup *cgrp, const char return 0; acquired = bpf_cgroup_acquire(cgrp); - bpf_cgroup_release(acquired); + if (!acquired) + err = 1; + else + bpf_cgroup_release(acquired); return 0; } -- 2.7.4