From 784cdf931543805120aed1e1c43df8e6fa436a55 Mon Sep 17 00:00:00 2001 From: Mykyta Yatsenko Date: Sun, 26 Oct 2025 20:38:53 +0000 Subject: selftests/bpf: add file dynptr tests Introducing selftests for validating file-backed dynptr works as expected. * validate implementation supports dynptr slice and read operations * validate destructors should be paired with initializers * validate sleepable progs can page in. Signed-off-by: Mykyta Yatsenko Reviewed-by: Eduard Zingerman Link: https://lore.kernel.org/r/20251026203853.135105-11-mykyta.yatsenko5@gmail.com Signed-off-by: Alexei Starovoitov --- tools/testing/selftests/bpf/progs/file_reader.c | 145 ++++++++++++++++++++++++ 1 file changed, 145 insertions(+) create mode 100644 tools/testing/selftests/bpf/progs/file_reader.c (limited to 'tools/testing/selftests/bpf/progs/file_reader.c') diff --git a/tools/testing/selftests/bpf/progs/file_reader.c b/tools/testing/selftests/bpf/progs/file_reader.c new file mode 100644 index 000000000000..2585f83b0ce5 --- /dev/null +++ b/tools/testing/selftests/bpf/progs/file_reader.c @@ -0,0 +1,145 @@ +// SPDX-License-Identifier: GPL-2.0 +/* Copyright (c) 2025 Meta Platforms, Inc. and affiliates. */ + +#include +#include +#include +#include +#include "bpf_misc.h" +#include "errno.h" + +char _license[] SEC("license") = "GPL"; + +struct { + __uint(type, BPF_MAP_TYPE_ARRAY); + __uint(max_entries, 1); + __type(key, int); + __type(value, struct elem); +} arrmap SEC(".maps"); + +struct elem { + struct file *file; + struct bpf_task_work tw; +}; + +char user_buf[256000]; +char tmp_buf[256000]; + +int pid = 0; +int err, run_success = 0; + +static int validate_file_read(struct file *file); +static int task_work_callback(struct bpf_map *map, void *key, void *value); + +SEC("lsm/file_open") +int on_open_expect_fault(void *c) +{ + struct bpf_dynptr dynptr; + struct file *file; + int local_err = 1; + __u32 user_buf_sz = sizeof(user_buf); + + if (bpf_get_current_pid_tgid() >> 32 != pid) + return 0; + + file = bpf_get_task_exe_file(bpf_get_current_task_btf()); + if (!file) + return 0; + + if (bpf_dynptr_from_file(file, 0, &dynptr)) + goto out; + + local_err = bpf_dynptr_read(tmp_buf, user_buf_sz, &dynptr, 0, 0); + if (local_err == -EFAULT) { /* Expect page fault */ + local_err = 0; + run_success = 1; + } +out: + bpf_dynptr_file_discard(&dynptr); + if (local_err) + err = local_err; + bpf_put_file(file); + return 0; +} + +SEC("lsm/file_open") +int on_open_validate_file_read(void *c) +{ + struct task_struct *task = bpf_get_current_task_btf(); + struct elem *work; + int key = 0; + + if (bpf_get_current_pid_tgid() >> 32 != pid) + return 0; + + work = bpf_map_lookup_elem(&arrmap, &key); + if (!work) { + err = 1; + return 0; + } + bpf_task_work_schedule_signal(task, &work->tw, &arrmap, task_work_callback, NULL); + return 0; +} + +/* Called in a sleepable context, read 256K bytes, cross check with user space read data */ +static int task_work_callback(struct bpf_map *map, void *key, void *value) +{ + struct task_struct *task = bpf_get_current_task_btf(); + struct file *file = bpf_get_task_exe_file(task); + + if (!file) + return 0; + + err = validate_file_read(file); + if (!err) + run_success = 1; + bpf_put_file(file); + return 0; +} + +static int verify_dynptr_read(struct bpf_dynptr *ptr, u32 off, char *user_buf, u32 len) +{ + int i; + + if (bpf_dynptr_read(tmp_buf, len, ptr, off, 0)) + return 1; + + /* Verify file contents read from BPF is the same as the one read from userspace */ + bpf_for(i, 0, len) + { + if (tmp_buf[i] != user_buf[i]) + return 1; + } + return 0; +} + +static int validate_file_read(struct file *file) +{ + struct bpf_dynptr dynptr; + int loc_err = 1, off; + __u32 user_buf_sz = sizeof(user_buf); + + if (bpf_dynptr_from_file(file, 0, &dynptr)) + goto cleanup; + + loc_err = verify_dynptr_read(&dynptr, 0, user_buf, user_buf_sz); + off = 1; + loc_err = loc_err ?: verify_dynptr_read(&dynptr, off, user_buf + off, user_buf_sz - off); + off = user_buf_sz - 1; + loc_err = loc_err ?: verify_dynptr_read(&dynptr, off, user_buf + off, user_buf_sz - off); + /* Read file with random offset and length */ + off = 4097; + loc_err = loc_err ?: verify_dynptr_read(&dynptr, off, user_buf + off, 100); + + /* Adjust dynptr, verify read */ + loc_err = loc_err ?: bpf_dynptr_adjust(&dynptr, off, off + 1); + loc_err = loc_err ?: verify_dynptr_read(&dynptr, 0, user_buf + off, 1); + /* Can't read more than 1 byte */ + loc_err = loc_err ?: verify_dynptr_read(&dynptr, 0, user_buf + off, 2) == 0; + /* Can't read with far offset */ + loc_err = loc_err ?: verify_dynptr_read(&dynptr, 1, user_buf + off, 1) == 0; + +cleanup: + bpf_dynptr_file_discard(&dynptr); + return loc_err; +} -- cgit v1.2.3 From 5913e936f6d5d348e33190885131c4f4eaa4bc4b Mon Sep 17 00:00:00 2001 From: Mykyta Yatsenko Date: Wed, 29 Oct 2025 19:59:07 +0000 Subject: selftests/bpf: Fix intermittent failures in file_reader test file_reader/on_open_expect_fault intermittently fails when test_progs runs tests in parallel, because it expects a page fault on first read. Another file_reader test running concurrently may have already pulled the same pages into the page cache, eliminating the fault and causing a spurious failure. Make file_reader/on_open_expect_fault read from a file region that does not overlap with other file_reader tests, so the initial access still faults even under parallel execution. Signed-off-by: Mykyta Yatsenko Acked-by: Ihor Solodrai Link: https://lore.kernel.org/r/20251029195907.858217-1-mykyta.yatsenko5@gmail.com Signed-off-by: Alexei Starovoitov --- tools/testing/selftests/bpf/progs/file_reader.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'tools/testing/selftests/bpf/progs/file_reader.c') diff --git a/tools/testing/selftests/bpf/progs/file_reader.c b/tools/testing/selftests/bpf/progs/file_reader.c index 2585f83b0ce5..166c3ac6957d 100644 --- a/tools/testing/selftests/bpf/progs/file_reader.c +++ b/tools/testing/selftests/bpf/progs/file_reader.c @@ -49,7 +49,7 @@ int on_open_expect_fault(void *c) if (bpf_dynptr_from_file(file, 0, &dynptr)) goto out; - local_err = bpf_dynptr_read(tmp_buf, user_buf_sz, &dynptr, 0, 0); + local_err = bpf_dynptr_read(tmp_buf, user_buf_sz, &dynptr, user_buf_sz, 0); if (local_err == -EFAULT) { /* Expect page fault */ local_err = 0; run_success = 1; -- cgit v1.2.3 From a4d31f451d5be2a65cfe8459808948071e9b54a0 Mon Sep 17 00:00:00 2001 From: Mykyta Yatsenko Date: Wed, 5 Nov 2025 13:21:05 +0000 Subject: selftests/bpf: Align kfuncs renamed in bpf tree bpf_task_work_schedule_resume() and bpf_task_work_schedule_signal() have been renamed in bpf tree to bpf_task_work_schedule_resume_impl() and bpf_task_work_schedule_signal_impl() accordingly. There are few uses of these kfuncs in selftests that are not in bpf tree, so that when we port [1] into bpf-next, those BPF programs will not compile. This patch aligns those remaining callsites with the kfunc renaming. It should go on top of [1] when applying on bpf-next. 1: https://lore.kernel.org/all/20251104-implv2-v3-0-4772b9ae0e06@meta.com/ Signed-off-by: Mykyta Yatsenko Link: https://lore.kernel.org/r/20251105132105.597344-1-mykyta.yatsenko5@gmail.com Signed-off-by: Alexei Starovoitov --- tools/testing/selftests/bpf/progs/file_reader.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'tools/testing/selftests/bpf/progs/file_reader.c') diff --git a/tools/testing/selftests/bpf/progs/file_reader.c b/tools/testing/selftests/bpf/progs/file_reader.c index 166c3ac6957d..4d756b623557 100644 --- a/tools/testing/selftests/bpf/progs/file_reader.c +++ b/tools/testing/selftests/bpf/progs/file_reader.c @@ -77,7 +77,7 @@ int on_open_validate_file_read(void *c) err = 1; return 0; } - bpf_task_work_schedule_signal(task, &work->tw, &arrmap, task_work_callback, NULL); + bpf_task_work_schedule_signal_impl(task, &work->tw, &arrmap, task_work_callback, NULL); return 0; } -- cgit v1.2.3