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Message-Id: <20230411041633.179404-1-void@manifault.com>
Date: Mon, 10 Apr 2023 23:16:31 -0500
From: David Vernet <void@...ifault.com>
To: bpf@...r.kernel.org
Cc: ast@...nel.org, daniel@...earbox.net, andrii@...nel.org,
martin.lau@...ux.dev, song@...nel.org, yhs@...com,
john.fastabend@...il.com, kpsingh@...nel.org, sdf@...gle.com,
haoluo@...gle.com, jolsa@...nel.org, linux-kernel@...r.kernel.org,
kernel-team@...a.com
Subject: [PATCH bpf-next 1/3] 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 <void@...ifault.com>
---
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 b6a5cda5bb59..71f0604bdc97 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 d0b7cd0d09d7..b0e279f4652b 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 48b2034cadb3..49347f12de39 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 030aff700084..e9dbd1af05a7 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;
}
--
2.40.0
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