selftests/bpf: Add tests for bpf_copy_from_user_str kfunc.

This adds tests for both the happy path and
the error path.

Signed-off-by: Jordan Rome <linux@jordanrome.com>
Link: https://lore.kernel.org/r/20240823195101.3621028-2-linux@jordanrome.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

tools/testing/selftests/bpf/prog_tests/attach_probe.c

@@ -283,9 +283,11 @@ static void test_uprobe_sleepable(struct test_attach_probe *skel)
 	trigger_func3();
 
 	ASSERT_EQ(skel->bss->uprobe_byname3_sleepable_res, 9, "check_uprobe_byname3_sleepable_res");
-	ASSERT_EQ(skel->bss->uprobe_byname3_res, 10, "check_uprobe_byname3_res");
-	ASSERT_EQ(skel->bss->uretprobe_byname3_sleepable_res, 11, "check_uretprobe_byname3_sleepable_res");
-	ASSERT_EQ(skel->bss->uretprobe_byname3_res, 12, "check_uretprobe_byname3_res");
+	ASSERT_EQ(skel->bss->uprobe_byname3_str_sleepable_res, 10, "check_uprobe_byname3_str_sleepable_res");
+	ASSERT_EQ(skel->bss->uprobe_byname3_res, 11, "check_uprobe_byname3_res");
+	ASSERT_EQ(skel->bss->uretprobe_byname3_sleepable_res, 12, "check_uretprobe_byname3_sleepable_res");
+	ASSERT_EQ(skel->bss->uretprobe_byname3_str_sleepable_res, 13, "check_uretprobe_byname3_str_sleepable_res");
+	ASSERT_EQ(skel->bss->uretprobe_byname3_res, 14, "check_uretprobe_byname3_res");
 }
 
 void test_attach_probe(void)

tools/testing/selftests/bpf/prog_tests/read_vsyscall.c

@@ -23,6 +23,7 @@ struct read_ret_desc {
 	{ .name = "probe_read_user_str", .ret = -EFAULT },
 	{ .name = "copy_from_user", .ret = -EFAULT },
 	{ .name = "copy_from_user_task", .ret = -EFAULT },
+	{ .name = "copy_from_user_str", .ret = -EFAULT },
 };
 
 void test_read_vsyscall(void)

tools/testing/selftests/bpf/progs/read_vsyscall.c

@@ -1,5 +1,6 @@
 // SPDX-License-Identifier: GPL-2.0
 /* Copyright (C) 2024. Huawei Technologies Co., Ltd */
+#include "vmlinux.h"
 #include <linux/types.h>
 #include <bpf/bpf_helpers.h>
 
@@ -7,10 +8,15 @@
 
 int target_pid = 0;
 void *user_ptr = 0;
-int read_ret[8];
+int read_ret[9];
 
 char _license[] SEC("license") = "GPL";
 
+/*
+ * This is the only kfunc, the others are helpers
+ */
+int bpf_copy_from_user_str(void *dst, u32, const void *, u64) __weak __ksym;
+
 SEC("fentry/" SYS_PREFIX "sys_nanosleep")
 int do_probe_read(void *ctx)
 {
@@ -40,6 +46,7 @@ int do_copy_from_user(void *ctx)
 	read_ret[6] = bpf_copy_from_user(buf, sizeof(buf), user_ptr);
 	read_ret[7] = bpf_copy_from_user_task(buf, sizeof(buf), user_ptr,
 					      bpf_get_current_task_btf(), 0);
+	read_ret[8] = bpf_copy_from_user_str((char *)buf, sizeof(buf), user_ptr, 0);
 
 	return 0;
 }

tools/testing/selftests/bpf/progs/test_attach_probe.c

@@ -5,8 +5,10 @@
 #include <bpf/bpf_helpers.h>
 #include <bpf/bpf_tracing.h>
 #include <bpf/bpf_core_read.h>
+#include <errno.h>
 #include "bpf_misc.h"
 
+u32 dynamic_sz = 1;
 int kprobe2_res = 0;
 int kretprobe2_res = 0;
 int uprobe_byname_res = 0;
@@ -14,11 +16,15 @@ int uretprobe_byname_res = 0;
 int uprobe_byname2_res = 0;
 int uretprobe_byname2_res = 0;
 int uprobe_byname3_sleepable_res = 0;
+int uprobe_byname3_str_sleepable_res = 0;
 int uprobe_byname3_res = 0;
 int uretprobe_byname3_sleepable_res = 0;
+int uretprobe_byname3_str_sleepable_res = 0;
 int uretprobe_byname3_res = 0;
 void *user_ptr = 0;
 
+int bpf_copy_from_user_str(void *dst, u32, const void *, u64) __weak __ksym;
+
 SEC("ksyscall/nanosleep")
 int BPF_KSYSCALL(handle_kprobe_auto, struct __kernel_timespec *req, struct __kernel_timespec *rem)
 {
@@ -87,11 +93,61 @@ static __always_inline bool verify_sleepable_user_copy(void)
 	return bpf_strncmp(data, sizeof(data), "test_data") == 0;
 }
 
+static __always_inline bool verify_sleepable_user_copy_str(void)
+{
+	int ret;
+	char data_long[20];
+	char data_long_pad[20];
+	char data_long_err[20];
+	char data_short[4];
+	char data_short_pad[4];
+
+	ret = bpf_copy_from_user_str(data_short, sizeof(data_short), user_ptr, 0);
+
+	if (bpf_strncmp(data_short, 4, "tes\0") != 0 || ret != 4)
+		return false;
+
+	ret = bpf_copy_from_user_str(data_short_pad, sizeof(data_short_pad), user_ptr, BPF_F_PAD_ZEROS);
+
+	if (bpf_strncmp(data_short, 4, "tes\0") != 0 || ret != 4)
+		return false;
+
+	/* Make sure this passes the verifier */
+	ret = bpf_copy_from_user_str(data_long, dynamic_sz & sizeof(data_long), user_ptr, 0);
+
+	if (ret != 0)
+		return false;
+
+	ret = bpf_copy_from_user_str(data_long, sizeof(data_long), user_ptr, 0);
+
+	if (bpf_strncmp(data_long, 10, "test_data\0") != 0 || ret != 10)
+		return false;
+
+	ret = bpf_copy_from_user_str(data_long_pad, sizeof(data_long_pad), user_ptr, BPF_F_PAD_ZEROS);
+
+	if (bpf_strncmp(data_long_pad, 10, "test_data\0") != 0 || ret != 10 || data_long_pad[19] != '\0')
+		return false;
+
+	ret = bpf_copy_from_user_str(data_long_err, sizeof(data_long_err), (void *)data_long, BPF_F_PAD_ZEROS);
+
+	if (ret > 0 || data_long_err[19] != '\0')
+		return false;
+
+	ret = bpf_copy_from_user_str(data_long, sizeof(data_long), user_ptr, 2);
+
+	if (ret != -EINVAL)
+		return false;
+
+	return true;
+}
+
 SEC("uprobe.s//proc/self/exe:trigger_func3")
 int handle_uprobe_byname3_sleepable(struct pt_regs *ctx)
 {
 	if (verify_sleepable_user_copy())
 		uprobe_byname3_sleepable_res = 9;
+	if (verify_sleepable_user_copy_str())
+		uprobe_byname3_str_sleepable_res = 10;
 	return 0;
 }
 
@@ -102,7 +158,7 @@ int handle_uprobe_byname3_sleepable(struct pt_regs *ctx)
 SEC("uprobe//proc/self/exe:trigger_func3")
 int handle_uprobe_byname3(struct pt_regs *ctx)
 {
-	uprobe_byname3_res = 10;
+	uprobe_byname3_res = 11;
 	return 0;
 }
 
@@ -110,14 +166,16 @@ SEC("uretprobe.s//proc/self/exe:trigger_func3")
 int handle_uretprobe_byname3_sleepable(struct pt_regs *ctx)
 {
 	if (verify_sleepable_user_copy())
-		uretprobe_byname3_sleepable_res = 11;
+		uretprobe_byname3_sleepable_res = 12;
+	if (verify_sleepable_user_copy_str())
+		uretprobe_byname3_str_sleepable_res = 13;
 	return 0;
 }
 
 SEC("uretprobe//proc/self/exe:trigger_func3")
 int handle_uretprobe_byname3(struct pt_regs *ctx)
 {
-	uretprobe_byname3_res = 12;
+	uretprobe_byname3_res = 14;
 	return 0;
 }