On 8/9/24 14:23, Jordan Rome wrote:
This adds a kfunc wrapper around strncpy_from_user,
which can be called from sleepable BPF programs.
This matches the non-sleepable 'bpf_probe_read_user_str'
helper.
Signed-off-by: Jordan Rome <linux@xxxxxxxxxxxxxx>
---
kernel/bpf/helpers.c | 26 +++++++++++++++++++
.../selftests/bpf/prog_tests/attach_probe.c | 8 +++---
.../selftests/bpf/prog_tests/read_vsyscall.c | 1 +
.../selftests/bpf/progs/read_vsyscall.c | 9 ++++++-
.../selftests/bpf/progs/test_attach_probe.c | 24 ++++++++++++++---
5 files changed, 61 insertions(+), 7 deletions(-)
diff --git a/kernel/bpf/helpers.c b/kernel/bpf/helpers.c
index d02ae323996b..455cac7b2631 100644
--- a/kernel/bpf/helpers.c
+++ b/kernel/bpf/helpers.c
@@ -2939,6 +2939,31 @@ __bpf_kfunc void bpf_iter_bits_destroy(struct bpf_iter_bits *it)
bpf_mem_free(&bpf_global_ma, kit->bits);
}
+/**
+ * bpf_copy_from_user_str() - Copy a string from an unsafe user address
+ * @dst: Destination address, in kernel space. This buffer must be at
+ * least @dst__szk bytes long.
+ * @dst__szk: Maximum number of bytes to copy, including the trailing NUL.
+ * @unsafe_ptr__ign: Source address, in user space.
+ *
+ * Copies a NUL-terminated string from userspace to BPF space. If user string is
+ * too long this will still ensure zero termination in the dst buffer unless
+ * buffer size is 0.
+ */
+__bpf_kfunc int bpf_copy_from_user_str(void *dst, u32 dst__szk, const void __user *unsafe_ptr__ign)
+{
+ int ret;
+
+ if (unlikely(!dst__szk))
+ return 0;
+
+ ret = strncpy_from_user(dst, unsafe_ptr__ign, dst__szk);
Does this function promise dst is null terminated if ret >= 0?
It seems not to have null at the end if the source string is longer than
dst_szk.
+ if (unlikely(ret < 0))
+ memset(dst, 0, dst__szk);
+
+ return ret;
+}
+
__bpf_kfunc_end_defs();
BTF_KFUNCS_START(generic_btf_ids)
@@ -3024,6 +3049,7 @@ BTF_ID_FLAGS(func, bpf_preempt_enable)
BTF_ID_FLAGS(func, bpf_iter_bits_new, KF_ITER_NEW)
BTF_ID_FLAGS(func, bpf_iter_bits_next, KF_ITER_NEXT | KF_RET_NULL)
BTF_ID_FLAGS(func, bpf_iter_bits_destroy, KF_ITER_DESTROY)
+BTF_ID_FLAGS(func, bpf_copy_from_user_str, KF_SLEEPABLE)
BTF_KFUNCS_END(common_btf_ids)
static const struct btf_kfunc_id_set common_kfunc_set = {
diff --git a/tools/testing/selftests/bpf/prog_tests/attach_probe.c b/tools/testing/selftests/bpf/prog_tests/attach_probe.c
index 7175af39134f..329c7862b52d 100644
--- a/tools/testing/selftests/bpf/prog_tests/attach_probe.c
+++ b/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)
diff --git a/tools/testing/selftests/bpf/prog_tests/read_vsyscall.c b/tools/testing/selftests/bpf/prog_tests/read_vsyscall.c
index 3405923fe4e6..c7b9ba8b1d06 100644
--- a/tools/testing/selftests/bpf/prog_tests/read_vsyscall.c
+++ b/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)
diff --git a/tools/testing/selftests/bpf/progs/read_vsyscall.c b/tools/testing/selftests/bpf/progs/read_vsyscall.c
index 986f96687ae1..27de1e907754 100644
--- a/tools/testing/selftests/bpf/progs/read_vsyscall.c
+++ b/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 *) __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);
return 0;
}
diff --git a/tools/testing/selftests/bpf/progs/test_attach_probe.c b/tools/testing/selftests/bpf/progs/test_attach_probe.c
index 68466a6ad18c..a90fa0bf103b 100644
--- a/tools/testing/selftests/bpf/progs/test_attach_probe.c
+++ b/tools/testing/selftests/bpf/progs/test_attach_probe.c
@@ -14,11 +14,15 @@ 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 *) __weak __ksym;
+
SEC("ksyscall/nanosleep")
int BPF_KSYSCALL(handle_kprobe_auto, struct __kernel_timespec *req, struct __kernel_timespec *rem)
{
@@ -87,11 +91,23 @@ 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[10];
+
+ ret = bpf_copy_from_user_str(data, sizeof(data), user_ptr);
+
+ return bpf_strncmp(data, sizeof(data), "test_data") == 0 && ret == 9;
+}
+
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 +118,7 @@ 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 +126,16 @@ 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;
}
--
2.44.1
