selftests/bpf: Fix rcu_read_lock test with new MEM_RCU semantics

Add MEM_RCU pointer null checking for related tests. Also
modified task_acquire test so it takes a rcu ptr 'ptr' where
'ptr = rcu_ptr->rcu_field'.

Signed-off-by: Yonghong Song <yhs@fb.com>
Link: https://lore.kernel.org/r/20221203184607.478314-1-yhs@fb.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

diff --git a/tools/testing/selftests/bpf/progs/rcu_read_lock.c b/tools/testing/selftests/bpf/progs/rcu_read_lock.c
index 94a9700..cf06a34 100644 (file)
--- a/tools/testing/selftests/bpf/progs/rcu_read_lock.c
+++ b/tools/testing/selftests/bpf/progs/rcu_read_lock.c
@@ -23,13 +23,14 @@ struct bpf_key *bpf_lookup_user_key(__u32 serial, __u64 flags) __ksym;
 void bpf_key_put(struct bpf_key *key) __ksym;
 void bpf_rcu_read_lock(void) __ksym;
 void bpf_rcu_read_unlock(void) __ksym;
-struct task_struct *bpf_task_acquire(struct task_struct *p) __ksym;
+struct task_struct *bpf_task_acquire_not_zero(struct task_struct *p) __ksym;
 void bpf_task_release(struct task_struct *p) __ksym;
 
 SEC("?fentry.s/" SYS_PREFIX "sys_getpgid")
 int get_cgroup_id(void *ctx)
 {
        struct task_struct *task;
+       struct css_set *cgroups;
 
        task = bpf_get_current_task_btf();
        if (task->pid != target_pid)
@@ -37,7 +38,11 @@ int get_cgroup_id(void *ctx)
 
        /* simulate bpf_get_current_cgroup_id() helper */
        bpf_rcu_read_lock();
-       cgroup_id = task->cgroups->dfl_cgrp->kn->id;
+       cgroups = task->cgroups;
+       if (!cgroups)
+               goto unlock;
+       cgroup_id = cgroups->dfl_cgrp->kn->id;
+unlock:
        bpf_rcu_read_unlock();
        return 0;
 }
@@ -56,6 +61,8 @@ int task_succ(void *ctx)
        bpf_rcu_read_lock();
        /* region including helper using rcu ptr real_parent */
        real_parent = task->real_parent;
+       if (!real_parent)
+               goto out;
        ptr = bpf_task_storage_get(&map_a, real_parent, &init_val,
                                   BPF_LOCAL_STORAGE_GET_F_CREATE);
        if (!ptr)
@@ -92,7 +99,10 @@ int two_regions(void *ctx)
        bpf_rcu_read_unlock();
        bpf_rcu_read_lock();
        real_parent = task->real_parent;
+       if (!real_parent)
+               goto out;
        (void)bpf_task_storage_get(&map_a, real_parent, 0, 0);
+out:
        bpf_rcu_read_unlock();
        return 0;
 }
@@ -105,7 +115,10 @@ int non_sleepable_1(void *ctx)
        task = bpf_get_current_task_btf();
        bpf_rcu_read_lock();
        real_parent = task->real_parent;
+       if (!real_parent)
+               goto out;
        (void)bpf_task_storage_get(&map_a, real_parent, 0, 0);
+out:
        bpf_rcu_read_unlock();
        return 0;
 }
@@ -121,7 +134,10 @@ int non_sleepable_2(void *ctx)
 
        bpf_rcu_read_lock();
        real_parent = task->real_parent;
+       if (!real_parent)
+               goto out;
        (void)bpf_task_storage_get(&map_a, real_parent, 0, 0);
+out:
        bpf_rcu_read_unlock();
        return 0;
 }
@@ -129,16 +145,28 @@ int non_sleepable_2(void *ctx)
 SEC("?fentry.s/" SYS_PREFIX "sys_nanosleep")
 int task_acquire(void *ctx)
 {
-       struct task_struct *task, *real_parent;
+       struct task_struct *task, *real_parent, *gparent;
 
        task = bpf_get_current_task_btf();
        bpf_rcu_read_lock();
        real_parent = task->real_parent;
+       if (!real_parent)
+               goto out;
+
+       /* rcu_ptr->rcu_field */
+       gparent = real_parent->real_parent;
+       if (!gparent)
+               goto out;
+
        /* acquire a reference which can be used outside rcu read lock region */
-       real_parent = bpf_task_acquire(real_parent);
+       gparent = bpf_task_acquire_not_zero(gparent);
+       if (!gparent)
+               goto out;
+
+       (void)bpf_task_storage_get(&map_a, gparent, 0, 0);
+       bpf_task_release(gparent);
+out:
        bpf_rcu_read_unlock();
-       (void)bpf_task_storage_get(&map_a, real_parent, 0, 0);
-       bpf_task_release(real_parent);
        return 0;
 }
 
@@ -181,9 +209,12 @@ int non_sleepable_rcu_mismatch(void *ctx)
        /* non-sleepable: missing bpf_rcu_read_unlock() in one path */
        bpf_rcu_read_lock();
        real_parent = task->real_parent;
+       if (!real_parent)
+               goto out;
        (void)bpf_task_storage_get(&map_a, real_parent, 0, 0);
        if (real_parent)
                bpf_rcu_read_unlock();
+out:
        return 0;
 }
 
@@ -199,16 +230,17 @@ int inproper_sleepable_helper(void *ctx)
        /* sleepable helper in rcu read lock region */
        bpf_rcu_read_lock();
        real_parent = task->real_parent;
+       if (!real_parent)
+               goto out;
        regs = (struct pt_regs *)bpf_task_pt_regs(real_parent);
-       if (!regs) {
-               bpf_rcu_read_unlock();
-               return 0;
-       }
+       if (!regs)
+               goto out;
 
        ptr = (void *)PT_REGS_IP(regs);
        (void)bpf_copy_from_user_task(&value, sizeof(uint32_t), ptr, task, 0);
        user_data = value;
        (void)bpf_task_storage_get(&map_a, real_parent, 0, 0);
+out:
        bpf_rcu_read_unlock();
        return 0;
 }
@@ -239,7 +271,10 @@ int nested_rcu_region(void *ctx)
        bpf_rcu_read_lock();
        bpf_rcu_read_lock();
        real_parent = task->real_parent;
+       if (!real_parent)
+               goto out;
        (void)bpf_task_storage_get(&map_a, real_parent, 0, 0);
+out:
        bpf_rcu_read_unlock();
        bpf_rcu_read_unlock();
        return 0;