The verifier previously accepted a task kptr after the final spin unlock ended its RCU protection in a sleepable program. The pointer could then be used after the task was freed.
Add a negative test for that case. Add positive controls showing that the pointer remains valid in a non-sleepable program and while an explicit RCU read-side section is still active. Assisted-by: Codex:gpt-5.6-sol Assisted-by: ChatGPT:GPT-5.6-Pro Signed-off-by: Ning Ding <[email protected]> --- .../selftests/bpf/prog_tests/task_kfunc.c | 2 + .../selftests/bpf/progs/task_kfunc_common.h | 12 +++++ .../selftests/bpf/progs/task_kfunc_failure.c | 24 ++++++++++ .../selftests/bpf/progs/task_kfunc_success.c | 48 +++++++++++++++++++ 4 files changed, 86 insertions(+) diff --git a/tools/testing/selftests/bpf/prog_tests/task_kfunc.c b/tools/testing/selftests/bpf/prog_tests/task_kfunc.c index e6e95c1416e65..fbd7855712c1a 100644 --- a/tools/testing/selftests/bpf/prog_tests/task_kfunc.c +++ b/tools/testing/selftests/bpf/prog_tests/task_kfunc.c @@ -176,6 +176,8 @@ static const char * const success_tests[] = { "test_task_from_pid_current", "test_task_from_pid_invalid", "task_kfunc_acquire_trusted_walked", + "task_kfunc_acquire_after_spin_unlock_non_sleepable", + "task_kfunc_acquire_after_spin_unlock_explicit_rcu", "test_task_kfunc_flavor_relo", "test_task_kfunc_flavor_relo_not_found", }; diff --git a/tools/testing/selftests/bpf/progs/task_kfunc_common.h b/tools/testing/selftests/bpf/progs/task_kfunc_common.h index e9c4fea7a4bba..052c9d0e3e2a8 100644 --- a/tools/testing/selftests/bpf/progs/task_kfunc_common.h +++ b/tools/testing/selftests/bpf/progs/task_kfunc_common.h @@ -20,6 +20,18 @@ struct { __uint(max_entries, 1); } __tasks_kfunc_map SEC(".maps"); +struct task_kptr_lock_value { + struct bpf_spin_lock lock; + struct task_struct __kptr * task; +}; + +struct { + __uint(type, BPF_MAP_TYPE_ARRAY); + __type(key, int); + __type(value, struct task_kptr_lock_value); + __uint(max_entries, 1); +} task_kptr_lock_map SEC(".maps"); + struct task_struct *bpf_task_acquire(struct task_struct *p) __ksym; void bpf_task_release(struct task_struct *p) __ksym; struct task_struct *bpf_task_from_pid(s32 pid) __ksym; diff --git a/tools/testing/selftests/bpf/progs/task_kfunc_failure.c b/tools/testing/selftests/bpf/progs/task_kfunc_failure.c index 5c99b1e6532bf..c0e7216b34193 100644 --- a/tools/testing/selftests/bpf/progs/task_kfunc_failure.c +++ b/tools/testing/selftests/bpf/progs/task_kfunc_failure.c @@ -378,3 +378,27 @@ int BPF_PROG(task_kfunc_release_in_map, struct task_struct *task, u64 clone_flag return 0; } + +SEC("?fentry.s/" SYS_PREFIX "sys_getpgid") +__failure __msg("R1 must be a rcu pointer") +int BPF_PROG(task_kfunc_acquire_after_final_spin_unlock) +{ + struct task_kptr_lock_value *v; + struct task_struct *task, *acquired; + int key = 0; + + v = bpf_map_lookup_elem(&task_kptr_lock_map, &key); + if (!v) + return 0; + + bpf_spin_lock(&v->lock); + task = v->task; + bpf_spin_unlock(&v->lock); + if (!task) + return 0; + + acquired = bpf_task_acquire(task); + if (acquired) + bpf_task_release(acquired); + return 0; +} diff --git a/tools/testing/selftests/bpf/progs/task_kfunc_success.c b/tools/testing/selftests/bpf/progs/task_kfunc_success.c index d63a79ee33dce..2bab7634c9dfd 100644 --- a/tools/testing/selftests/bpf/progs/task_kfunc_success.c +++ b/tools/testing/selftests/bpf/progs/task_kfunc_success.c @@ -6,6 +6,7 @@ #include <bpf/bpf_helpers.h> #include "../bpf_experimental.h" +#include "bpf_misc.h" #include "task_kfunc_common.h" char _license[] SEC("license") = "GPL"; @@ -366,6 +367,53 @@ int BPF_PROG(task_kfunc_acquire_trusted_walked, struct task_struct *task, u64 cl return 0; } +SEC("fentry/" SYS_PREFIX "sys_getpgid") +int BPF_PROG(task_kfunc_acquire_after_spin_unlock_non_sleepable) +{ + struct task_kptr_lock_value *v; + struct task_struct *task, *acquired; + int key = 0; + + v = bpf_map_lookup_elem(&task_kptr_lock_map, &key); + if (!v) + return 0; + + bpf_spin_lock(&v->lock); + task = v->task; + bpf_spin_unlock(&v->lock); + if (!task) + return 0; + + acquired = bpf_task_acquire(task); + if (acquired) + bpf_task_release(acquired); + return 0; +} + +SEC("fentry.s/" SYS_PREFIX "sys_getpgid") +int BPF_PROG(task_kfunc_acquire_after_spin_unlock_explicit_rcu) +{ + struct task_kptr_lock_value *v; + struct task_struct *task, *acquired; + int key = 0; + + v = bpf_map_lookup_elem(&task_kptr_lock_map, &key); + if (!v) + return 0; + + bpf_rcu_read_lock(); + bpf_spin_lock(&v->lock); + task = v->task; + bpf_spin_unlock(&v->lock); + if (task) { + acquired = bpf_task_acquire(task); + if (acquired) + bpf_task_release(acquired); + } + bpf_rcu_read_unlock(); + return 0; +} + SEC("syscall") int test_task_from_vpid_current(const void *ctx) { -- 2.43.0
