Merge branch 'check-the-remaining-info_cnt-before-repeating-btf-fields'

Hou Tao says:

====================
Check the remaining info_cnt before repeating btf fields

From: Hou Tao <houtao1@huawei.com>

Hi,

The patch set adds the missed check again info_cnt when flattening the
array of nested struct. The problem was spotted when developing dynptr
key support for hash map. Patch #1 adds the missed check and patch #2
adds three success test cases and one failure test case for the problem.

Comments are always welcome.

Change Log:
v2:
 * patch #1: check info_cnt in btf_repeat_fields()
 * patch #2: use a hard-coded number instead of BTF_FIELDS_MAX, because
             BTF_FIELDS_MAX is not always available in vmlinux.h (e.g.,
	     for llvm 17/18)

v1: https://lore.kernel.org/bpf/20240911110557.2759801-1-houtao@huaweicloud.com/T/#t
====================

Link: https://lore.kernel.org/r/20241008071114.3718177-1-houtao@huaweicloud.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

kernel/bpf/btf.c

@@ -3523,7 +3523,7 @@ static int btf_get_field_type(const struct btf *btf, const struct btf_type *var_
  *   (i + 1) * elem_size
  * where i is the repeat index and elem_size is the size of an element.
  */
-static int btf_repeat_fields(struct btf_field_info *info,
+static int btf_repeat_fields(struct btf_field_info *info, int info_cnt,
 			     u32 field_cnt, u32 repeat_cnt, u32 elem_size)
 {
 	u32 i, j;
@@ -3543,6 +3543,12 @@ static int btf_repeat_fields(struct btf_field_info *info,
 		}
 	}
 
+	/* The type of struct size or variable size is u32,
+	 * so the multiplication will not overflow.
+	 */
+	if (field_cnt * (repeat_cnt + 1) > info_cnt)
+		return -E2BIG;
+
 	cur = field_cnt;
 	for (i = 0; i < repeat_cnt; i++) {
 		memcpy(&info[cur], &info[0], field_cnt * sizeof(info[0]));
@@ -3587,7 +3593,7 @@ static int btf_find_nested_struct(const struct btf *btf, const struct btf_type *
 		info[i].off += off;
 
 	if (nelems > 1) {
-		err = btf_repeat_fields(info, ret, nelems - 1, t->size);
+		err = btf_repeat_fields(info, info_cnt, ret, nelems - 1, t->size);
 		if (err == 0)
 			ret *= nelems;
 		else
@@ -3681,10 +3687,10 @@ static int btf_find_field_one(const struct btf *btf,
 
 	if (ret == BTF_FIELD_IGNORE)
 		return 0;
-	if (nelems > info_cnt)
+	if (!info_cnt)
 		return -E2BIG;
 	if (nelems > 1) {
-		ret = btf_repeat_fields(info, 1, nelems - 1, sz);
+		ret = btf_repeat_fields(info, info_cnt, 1, nelems - 1, sz);
 		if (ret < 0)
 			return ret;
 	}

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

@@ -23,6 +23,7 @@ static const char * const cpumask_success_testcases[] = {
 	"test_global_mask_array_l2_rcu",
 	"test_global_mask_nested_rcu",
 	"test_global_mask_nested_deep_rcu",
+	"test_global_mask_nested_deep_array_rcu",
 	"test_cpumask_weight",
 };
 

tools/testing/selftests/bpf/progs/cpumask_common.h

@@ -7,6 +7,11 @@
 #include "errno.h"
 #include <stdbool.h>
 
+/* Should use BTF_FIELDS_MAX, but it is not always available in vmlinux.h,
+ * so use the hard-coded number as a workaround.
+ */
+#define CPUMASK_KPTR_FIELDS_MAX 11
+
 int err;
 
 #define private(name) SEC(".bss." #name) __attribute__((aligned(8)))

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

@@ -10,6 +10,21 @@
 
 char _license[] SEC("license") = "GPL";
 
+struct kptr_nested_array_2 {
+	struct bpf_cpumask __kptr * mask;
+};
+
+struct kptr_nested_array_1 {
+	/* Make btf_parse_fields() in map_create() return -E2BIG */
+	struct kptr_nested_array_2 d_2[CPUMASK_KPTR_FIELDS_MAX + 1];
+};
+
+struct kptr_nested_array {
+	struct kptr_nested_array_1 d_1;
+};
+
+private(MASK_NESTED) static struct kptr_nested_array global_mask_nested_arr;
+
 /* Prototype for all of the program trace events below:
  *
  * TRACE_EVENT(task_newtask,
@@ -187,3 +202,23 @@ int BPF_PROG(test_global_mask_rcu_no_null_check, struct task_struct *task, u64 c
 
 	return 0;
 }
+
+SEC("tp_btf/task_newtask")
+__failure __msg("has no valid kptr")
+int BPF_PROG(test_invalid_nested_array, struct task_struct *task, u64 clone_flags)
+{
+	struct bpf_cpumask *local, *prev;
+
+	local = create_cpumask();
+	if (!local)
+		return 0;
+
+	prev = bpf_kptr_xchg(&global_mask_nested_arr.d_1.d_2[CPUMASK_KPTR_FIELDS_MAX].mask, local);
+	if (prev) {
+		bpf_cpumask_release(prev);
+		err = 3;
+		return 0;
+	}
+
+	return 0;
+}

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

@@ -31,11 +31,59 @@ struct kptr_nested_deep {
 	struct kptr_nested_pair ptr_pairs[3];
 };
 
+struct kptr_nested_deep_array_1_2 {
+	int dummy;
+	struct bpf_cpumask __kptr * mask[CPUMASK_KPTR_FIELDS_MAX];
+};
+
+struct kptr_nested_deep_array_1_1 {
+	int dummy;
+	struct kptr_nested_deep_array_1_2 d_2;
+};
+
+struct kptr_nested_deep_array_1 {
+	long dummy;
+	struct kptr_nested_deep_array_1_1 d_1;
+};
+
+struct kptr_nested_deep_array_2_2 {
+	long dummy[2];
+	struct bpf_cpumask __kptr * mask;
+};
+
+struct kptr_nested_deep_array_2_1 {
+	int dummy;
+	struct kptr_nested_deep_array_2_2 d_2[CPUMASK_KPTR_FIELDS_MAX];
+};
+
+struct kptr_nested_deep_array_2 {
+	long dummy;
+	struct kptr_nested_deep_array_2_1 d_1;
+};
+
+struct kptr_nested_deep_array_3_2 {
+	long dummy[2];
+	struct bpf_cpumask __kptr * mask;
+};
+
+struct kptr_nested_deep_array_3_1 {
+	int dummy;
+	struct kptr_nested_deep_array_3_2 d_2;
+};
+
+struct kptr_nested_deep_array_3 {
+	long dummy;
+	struct kptr_nested_deep_array_3_1 d_1[CPUMASK_KPTR_FIELDS_MAX];
+};
+
 private(MASK) static struct bpf_cpumask __kptr * global_mask_array[2];
 private(MASK) static struct bpf_cpumask __kptr * global_mask_array_l2[2][1];
 private(MASK) static struct bpf_cpumask __kptr * global_mask_array_one[1];
 private(MASK) static struct kptr_nested global_mask_nested[2];
 private(MASK_DEEP) static struct kptr_nested_deep global_mask_nested_deep;
+private(MASK_1) static struct kptr_nested_deep_array_1 global_mask_nested_deep_array_1;
+private(MASK_2) static struct kptr_nested_deep_array_2 global_mask_nested_deep_array_2;
+private(MASK_3) static struct kptr_nested_deep_array_3 global_mask_nested_deep_array_3;
 
 static bool is_test_task(void)
 {
@@ -543,12 +591,21 @@ static int _global_mask_array_rcu(struct bpf_cpumask **mask0,
 		goto err_exit;
 	}
 
-	/* [<mask 0>, NULL] */
-	if (!*mask0 || *mask1) {
+	/* [<mask 0>, *] */
+	if (!*mask0) {
 		err = 2;
 		goto err_exit;
 	}
 
+	if (!mask1)
+		goto err_exit;
+
+	/* [*, NULL] */
+	if (*mask1) {
+		err = 3;
+		goto err_exit;
+	}
+
 	local = create_cpumask();
 	if (!local) {
 		err = 9;
@@ -631,6 +688,23 @@ int BPF_PROG(test_global_mask_nested_deep_rcu, struct task_struct *task, u64 clo
 	return 0;
 }
 
+SEC("tp_btf/task_newtask")
+int BPF_PROG(test_global_mask_nested_deep_array_rcu, struct task_struct *task, u64 clone_flags)
+{
+	int i;
+
+	for (i = 0; i < CPUMASK_KPTR_FIELDS_MAX; i++)
+		_global_mask_array_rcu(&global_mask_nested_deep_array_1.d_1.d_2.mask[i], NULL);
+
+	for (i = 0; i < CPUMASK_KPTR_FIELDS_MAX; i++)
+		_global_mask_array_rcu(&global_mask_nested_deep_array_2.d_1.d_2[i].mask, NULL);
+
+	for (i = 0; i < CPUMASK_KPTR_FIELDS_MAX; i++)
+		_global_mask_array_rcu(&global_mask_nested_deep_array_3.d_1[i].d_2.mask, NULL);
+
+	return 0;
+}
+
 SEC("tp_btf/task_newtask")
 int BPF_PROG(test_cpumask_weight, struct task_struct *task, u64 clone_flags)
 {