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Subject[PATCH v13 17/18] kernel/sysctl-test: Add null pointer test for sysctl.c:proc_dointvec()
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From: Iurii Zaikin <yzaikin@google.com>

KUnit tests for initialized data behavior of proc_dointvec that is
explicitly checked in the code. Includes basic parsing tests including
int min/max overflow.

Signed-off-by: Iurii Zaikin <yzaikin@google.com>
Signed-off-by: Brendan Higgins <brendanhiggins@google.com>
Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Reviewed-by: Logan Gunthorpe <logang@deltatee.com>
Acked-by: Luis Chamberlain <mcgrof@kernel.org>
Reviewed-by: Stephen Boyd <sboyd@kernel.org>
---
kernel/Makefile | 2 +
kernel/sysctl-test.c | 392 +++++++++++++++++++++++++++++++++++++++++++
lib/Kconfig.debug | 11 ++
3 files changed, 405 insertions(+)
create mode 100644 kernel/sysctl-test.c

diff --git a/kernel/Makefile b/kernel/Makefile
index ef0d95a190b41..63e9ea6122c2c 100644
--- a/kernel/Makefile
+++ b/kernel/Makefile
@@ -113,6 +113,8 @@ obj-$(CONFIG_TORTURE_TEST) += torture.o
obj-$(CONFIG_HAS_IOMEM) += iomem.o
obj-$(CONFIG_RSEQ) += rseq.o

+obj-$(CONFIG_SYSCTL_KUNIT_TEST) += sysctl-test.o
+
obj-$(CONFIG_GCC_PLUGIN_STACKLEAK) += stackleak.o
KASAN_SANITIZE_stackleak.o := n
KCOV_INSTRUMENT_stackleak.o := n
diff --git a/kernel/sysctl-test.c b/kernel/sysctl-test.c
new file mode 100644
index 0000000000000..2a63241a8453b
--- /dev/null
+++ b/kernel/sysctl-test.c
@@ -0,0 +1,392 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * KUnit test of proc sysctl.
+ */
+
+#include <kunit/test.h>
+#include <linux/sysctl.h>
+
+#define KUNIT_PROC_READ 0
+#define KUNIT_PROC_WRITE 1
+
+static int i_zero;
+static int i_one_hundred = 100;
+
+/*
+ * Test that proc_dointvec will not try to use a NULL .data field even when the
+ * length is non-zero.
+ */
+static void sysctl_test_api_dointvec_null_tbl_data(struct kunit *test)
+{
+ struct ctl_table null_data_table = {
+ .procname = "foo",
+ /*
+ * Here we are testing that proc_dointvec behaves correctly when
+ * we give it a NULL .data field. Normally this would point to a
+ * piece of memory where the value would be stored.
+ */
+ .data = NULL,
+ .maxlen = sizeof(int),
+ .mode = 0644,
+ .proc_handler = proc_dointvec,
+ .extra1 = &i_zero,
+ .extra2 = &i_one_hundred,
+ };
+ /*
+ * proc_dointvec expects a buffer in user space, so we allocate one. We
+ * also need to cast it to __user so sparse doesn't get mad.
+ */
+ void __user *buffer = (void __user *)kunit_kzalloc(test, sizeof(int),
+ GFP_USER);
+ size_t len;
+ loff_t pos;
+
+ /*
+ * We don't care what the starting length is since proc_dointvec should
+ * not try to read because .data is NULL.
+ */
+ len = 1234;
+ KUNIT_EXPECT_EQ(test, 0, proc_dointvec(&null_data_table,
+ KUNIT_PROC_READ, buffer, &len,
+ &pos));
+ KUNIT_EXPECT_EQ(test, (size_t)0, len);
+
+ /*
+ * See above.
+ */
+ len = 1234;
+ KUNIT_EXPECT_EQ(test, 0, proc_dointvec(&null_data_table,
+ KUNIT_PROC_WRITE, buffer, &len,
+ &pos));
+ KUNIT_EXPECT_EQ(test, (size_t)0, len);
+}
+
+/*
+ * Similar to the previous test, we create a struct ctrl_table that has a .data
+ * field that proc_dointvec cannot do anything with; however, this time it is
+ * because we tell proc_dointvec that the size is 0.
+ */
+static void sysctl_test_api_dointvec_table_maxlen_unset(struct kunit *test)
+{
+ int data = 0;
+ struct ctl_table data_maxlen_unset_table = {
+ .procname = "foo",
+ .data = &data,
+ /*
+ * So .data is no longer NULL, but we tell proc_dointvec its
+ * length is 0, so it still shouldn't try to use it.
+ */
+ .maxlen = 0,
+ .mode = 0644,
+ .proc_handler = proc_dointvec,
+ .extra1 = &i_zero,
+ .extra2 = &i_one_hundred,
+ };
+ void __user *buffer = (void __user *)kunit_kzalloc(test, sizeof(int),
+ GFP_USER);
+ size_t len;
+ loff_t pos;
+
+ /*
+ * As before, we don't care what buffer length is because proc_dointvec
+ * cannot do anything because its internal .data buffer has zero length.
+ */
+ len = 1234;
+ KUNIT_EXPECT_EQ(test, 0, proc_dointvec(&data_maxlen_unset_table,
+ KUNIT_PROC_READ, buffer, &len,
+ &pos));
+ KUNIT_EXPECT_EQ(test, (size_t)0, len);
+
+ /*
+ * See previous comment.
+ */
+ len = 1234;
+ KUNIT_EXPECT_EQ(test, 0, proc_dointvec(&data_maxlen_unset_table,
+ KUNIT_PROC_WRITE, buffer, &len,
+ &pos));
+ KUNIT_EXPECT_EQ(test, (size_t)0, len);
+}
+
+/*
+ * Here we provide a valid struct ctl_table, but we try to read and write from
+ * it using a buffer of zero length, so it should still fail in a similar way as
+ * before.
+ */
+static void sysctl_test_api_dointvec_table_len_is_zero(struct kunit *test)
+{
+ int data = 0;
+ /* Good table. */
+ struct ctl_table table = {
+ .procname = "foo",
+ .data = &data,
+ .maxlen = sizeof(int),
+ .mode = 0644,
+ .proc_handler = proc_dointvec,
+ .extra1 = &i_zero,
+ .extra2 = &i_one_hundred,
+ };
+ void __user *buffer = (void __user *)kunit_kzalloc(test, sizeof(int),
+ GFP_USER);
+ /*
+ * However, now our read/write buffer has zero length.
+ */
+ size_t len = 0;
+ loff_t pos;
+
+ KUNIT_EXPECT_EQ(test, 0, proc_dointvec(&table, KUNIT_PROC_READ, buffer,
+ &len, &pos));
+ KUNIT_EXPECT_EQ(test, (size_t)0, len);
+
+ KUNIT_EXPECT_EQ(test, 0, proc_dointvec(&table, KUNIT_PROC_WRITE, buffer,
+ &len, &pos));
+ KUNIT_EXPECT_EQ(test, (size_t)0, len);
+}
+
+/*
+ * Test that proc_dointvec refuses to read when the file position is non-zero.
+ */
+static void sysctl_test_api_dointvec_table_read_but_position_set(
+ struct kunit *test)
+{
+ int data = 0;
+ /* Good table. */
+ struct ctl_table table = {
+ .procname = "foo",
+ .data = &data,
+ .maxlen = sizeof(int),
+ .mode = 0644,
+ .proc_handler = proc_dointvec,
+ .extra1 = &i_zero,
+ .extra2 = &i_one_hundred,
+ };
+ void __user *buffer = (void __user *)kunit_kzalloc(test, sizeof(int),
+ GFP_USER);
+ /*
+ * We don't care about our buffer length because we start off with a
+ * non-zero file position.
+ */
+ size_t len = 1234;
+ /*
+ * proc_dointvec should refuse to read into the buffer since the file
+ * pos is non-zero.
+ */
+ loff_t pos = 1;
+
+ KUNIT_EXPECT_EQ(test, 0, proc_dointvec(&table, KUNIT_PROC_READ, buffer,
+ &len, &pos));
+ KUNIT_EXPECT_EQ(test, (size_t)0, len);
+}
+
+/*
+ * Test that we can read a two digit number in a sufficiently size buffer.
+ * Nothing fancy.
+ */
+static void sysctl_test_dointvec_read_happy_single_positive(struct kunit *test)
+{
+ int data = 0;
+ /* Good table. */
+ struct ctl_table table = {
+ .procname = "foo",
+ .data = &data,
+ .maxlen = sizeof(int),
+ .mode = 0644,
+ .proc_handler = proc_dointvec,
+ .extra1 = &i_zero,
+ .extra2 = &i_one_hundred,
+ };
+ size_t len = 4;
+ loff_t pos = 0;
+ char *buffer = kunit_kzalloc(test, len, GFP_USER);
+ char __user *user_buffer = (char __user *)buffer;
+ /* Store 13 in the data field. */
+ *((int *)table.data) = 13;
+
+ KUNIT_EXPECT_EQ(test, 0, proc_dointvec(&table, KUNIT_PROC_READ,
+ user_buffer, &len, &pos));
+ KUNIT_ASSERT_EQ(test, (size_t)3, len);
+ buffer[len] = '\0';
+ /* And we read 13 back out. */
+ KUNIT_EXPECT_STREQ(test, "13\n", buffer);
+}
+
+/*
+ * Same as previous test, just now with negative numbers.
+ */
+static void sysctl_test_dointvec_read_happy_single_negative(struct kunit *test)
+{
+ int data = 0;
+ /* Good table. */
+ struct ctl_table table = {
+ .procname = "foo",
+ .data = &data,
+ .maxlen = sizeof(int),
+ .mode = 0644,
+ .proc_handler = proc_dointvec,
+ .extra1 = &i_zero,
+ .extra2 = &i_one_hundred,
+ };
+ size_t len = 5;
+ loff_t pos = 0;
+ char *buffer = kunit_kzalloc(test, len, GFP_USER);
+ char __user *user_buffer = (char __user *)buffer;
+ *((int *)table.data) = -16;
+
+ KUNIT_EXPECT_EQ(test, 0, proc_dointvec(&table, KUNIT_PROC_READ,
+ user_buffer, &len, &pos));
+ KUNIT_ASSERT_EQ(test, (size_t)4, len);
+ buffer[len] = '\0';
+ KUNIT_EXPECT_STREQ(test, "-16\n", (char *)buffer);
+}
+
+/*
+ * Test that a simple positive write works.
+ */
+static void sysctl_test_dointvec_write_happy_single_positive(struct kunit *test)
+{
+ int data = 0;
+ /* Good table. */
+ struct ctl_table table = {
+ .procname = "foo",
+ .data = &data,
+ .maxlen = sizeof(int),
+ .mode = 0644,
+ .proc_handler = proc_dointvec,
+ .extra1 = &i_zero,
+ .extra2 = &i_one_hundred,
+ };
+ char input[] = "9";
+ size_t len = sizeof(input) - 1;
+ loff_t pos = 0;
+ char *buffer = kunit_kzalloc(test, len, GFP_USER);
+ char __user *user_buffer = (char __user *)buffer;
+
+ memcpy(buffer, input, len);
+
+ KUNIT_EXPECT_EQ(test, 0, proc_dointvec(&table, KUNIT_PROC_WRITE,
+ user_buffer, &len, &pos));
+ KUNIT_EXPECT_EQ(test, sizeof(input) - 1, len);
+ KUNIT_EXPECT_EQ(test, sizeof(input) - 1, (size_t)pos);
+ KUNIT_EXPECT_EQ(test, 9, *((int *)table.data));
+}
+
+/*
+ * Same as previous test, but now with negative numbers.
+ */
+static void sysctl_test_dointvec_write_happy_single_negative(struct kunit *test)
+{
+ int data = 0;
+ struct ctl_table table = {
+ .procname = "foo",
+ .data = &data,
+ .maxlen = sizeof(int),
+ .mode = 0644,
+ .proc_handler = proc_dointvec,
+ .extra1 = &i_zero,
+ .extra2 = &i_one_hundred,
+ };
+ char input[] = "-9";
+ size_t len = sizeof(input) - 1;
+ loff_t pos = 0;
+ char *buffer = kunit_kzalloc(test, len, GFP_USER);
+ char __user *user_buffer = (char __user *)buffer;
+
+ memcpy(buffer, input, len);
+
+ KUNIT_EXPECT_EQ(test, 0, proc_dointvec(&table, KUNIT_PROC_WRITE,
+ user_buffer, &len, &pos));
+ KUNIT_EXPECT_EQ(test, sizeof(input) - 1, len);
+ KUNIT_EXPECT_EQ(test, sizeof(input) - 1, (size_t)pos);
+ KUNIT_EXPECT_EQ(test, -9, *((int *)table.data));
+}
+
+/*
+ * Test that writing a value smaller than the minimum possible value is not
+ * allowed.
+ */
+static void sysctl_test_api_dointvec_write_single_less_int_min(
+ struct kunit *test)
+{
+ int data = 0;
+ struct ctl_table table = {
+ .procname = "foo",
+ .data = &data,
+ .maxlen = sizeof(int),
+ .mode = 0644,
+ .proc_handler = proc_dointvec,
+ .extra1 = &i_zero,
+ .extra2 = &i_one_hundred,
+ };
+ size_t max_len = 32, len = max_len;
+ loff_t pos = 0;
+ char *buffer = kunit_kzalloc(test, max_len, GFP_USER);
+ char __user *user_buffer = (char __user *)buffer;
+ unsigned long abs_of_less_than_min = (unsigned long)INT_MAX
+ - (INT_MAX + INT_MIN) + 1;
+
+ /*
+ * We use this rigmarole to create a string that contains a value one
+ * less than the minimum accepted value.
+ */
+ KUNIT_ASSERT_LT(test,
+ (size_t)snprintf(buffer, max_len, "-%lu",
+ abs_of_less_than_min),
+ max_len);
+
+ KUNIT_EXPECT_EQ(test, -EINVAL, proc_dointvec(&table, KUNIT_PROC_WRITE,
+ user_buffer, &len, &pos));
+ KUNIT_EXPECT_EQ(test, max_len, len);
+ KUNIT_EXPECT_EQ(test, 0, *((int *)table.data));
+}
+
+/*
+ * Test that writing the maximum possible value works.
+ */
+static void sysctl_test_api_dointvec_write_single_greater_int_max(
+ struct kunit *test)
+{
+ int data = 0;
+ struct ctl_table table = {
+ .procname = "foo",
+ .data = &data,
+ .maxlen = sizeof(int),
+ .mode = 0644,
+ .proc_handler = proc_dointvec,
+ .extra1 = &i_zero,
+ .extra2 = &i_one_hundred,
+ };
+ size_t max_len = 32, len = max_len;
+ loff_t pos = 0;
+ char *buffer = kunit_kzalloc(test, max_len, GFP_USER);
+ char __user *user_buffer = (char __user *)buffer;
+ unsigned long greater_than_max = (unsigned long)INT_MAX + 1;
+
+ KUNIT_ASSERT_GT(test, greater_than_max, (unsigned long)INT_MAX);
+ KUNIT_ASSERT_LT(test, (size_t)snprintf(buffer, max_len, "%lu",
+ greater_than_max),
+ max_len);
+ KUNIT_EXPECT_EQ(test, -EINVAL, proc_dointvec(&table, KUNIT_PROC_WRITE,
+ user_buffer, &len, &pos));
+ KUNIT_ASSERT_EQ(test, max_len, len);
+ KUNIT_EXPECT_EQ(test, 0, *((int *)table.data));
+}
+
+static struct kunit_case sysctl_test_cases[] = {
+ KUNIT_CASE(sysctl_test_api_dointvec_null_tbl_data),
+ KUNIT_CASE(sysctl_test_api_dointvec_table_maxlen_unset),
+ KUNIT_CASE(sysctl_test_api_dointvec_table_len_is_zero),
+ KUNIT_CASE(sysctl_test_api_dointvec_table_read_but_position_set),
+ KUNIT_CASE(sysctl_test_dointvec_read_happy_single_positive),
+ KUNIT_CASE(sysctl_test_dointvec_read_happy_single_negative),
+ KUNIT_CASE(sysctl_test_dointvec_write_happy_single_positive),
+ KUNIT_CASE(sysctl_test_dointvec_write_happy_single_negative),
+ KUNIT_CASE(sysctl_test_api_dointvec_write_single_less_int_min),
+ KUNIT_CASE(sysctl_test_api_dointvec_write_single_greater_int_max),
+ {}
+};
+
+static struct kunit_suite sysctl_test_suite = {
+ .name = "sysctl_test",
+ .test_cases = sysctl_test_cases,
+};
+
+kunit_test_suite(sysctl_test_suite);
diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
index 5960e2980a8a0..a425741907b0d 100644
--- a/lib/Kconfig.debug
+++ b/lib/Kconfig.debug
@@ -1965,6 +1965,17 @@ config TEST_SYSCTL

If unsure, say N.

+config SYSCTL_KUNIT_TEST
+ bool "KUnit test for sysctl"
+ depends on KUNIT
+ help
+ This builds the proc sysctl unit test, which runs on boot.
+ Tests the API contract and implementation correctness of sysctl.
+ For more information on KUnit and unit tests in general please refer
+ to the KUnit documentation in Documentation/dev-tools/kunit/.
+
+ If unsure, say N.
+
config TEST_UDELAY
tristate "udelay test driver"
help
--
2.23.0.rc1.153.gdeed80330f-goog
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