Re: [PATCH v4 2/2] userns: Add KUnit test suite for uid_gid_map
From: Bradley Morgan
Date: Wed Aug 26 2026 - 18:28:40 EST
On 26 August 2026 23:00:35 BST, Bill Wendling <morbo@xxxxxxxxxx> wrote:
>Add a KUnit test suite to verify the insertion and sorting of mappings
>in struct uid_gid_map. This test suite validates both base extent
>insertion (<= 5 mappings) and extended extent insertion (> 5 mappings,
>which triggers the allocation of the forward and reverse pointers).
>
>This is especially useful for verifying that the __counted_by_ptr
>attribute added to 'forward' and 'reverse' pointers works correctly
>without causing any runtime bounds-checking panics or traps.
>
>Assisted-by: Gemini:3.1-pro-preview
Now for all the work s/you/your AI done, I've done the tests and they
passed, and they LGTM
Tested-by: Bradley Morgan <brads@xxxxxxxxxxxxxx>
Reviewed-by: Bradley Morgan <brads@xxxxxxxxxxxxxx>
Thanks for your patch mate, (pls slow down tho, we can review oh so quick)
>Signed-off-by: Bill Wendling <morbo@xxxxxxxxxx>
>---
>v2 - Remove Gerrit tag.
>v3 - s/KUNIT_EXPECT_NOT_ERR_OR_NULL/KUNIT_ASSERT_NOT_ERR_OR_NULL/
> - Fixed Kconfig tests.
>v4 - Actually test on unsorted data. Corrected the "Assisted-by" tag.
>---
>Cc: Bradley Morgan <brads@xxxxxxxxxxxxxx>
>Cc: Thomas Weißschuh <thomas.weissschuh@xxxxxxxxxxxxx>
>Cc: Kees Cook <kees@xxxxxxxxxx>
>Cc: "Gustavo A. R. Silva" <gustavoars@xxxxxxxxxx>
>Cc: Christian Brauner <brauner@xxxxxxxxxx>
>Cc: Aleksa Sarai <cyphar@xxxxxxxxxx>
>Cc: Jan Kara <jack@xxxxxxx>
>Cc: Nathan Chancellor <nathan@xxxxxxxxxx>
>Cc: Miguel Ojeda <ojeda@xxxxxxxxxx>
>Cc: Thomas Gleixner <tglx@xxxxxxxxxx>
>Cc: Nicolas Schier <nsc@xxxxxxxxxx>
>Cc: Gary Guo <gary@xxxxxxxxxxx>
>Cc: "Thomas Weißschuh" <thomas.weissschuh@xxxxxxxxxxxxx>
>Cc: Alice Ryhl <aliceryhl@xxxxxxxxxx>
>Cc: Douglas Anderson <dianders@xxxxxxxxxxxx>
>Cc: Anand Moon <linux.amoon@xxxxxxxxx>
>Cc: Oleg Nesterov <oleg@xxxxxxxxxx>
>Cc: codemender-patching+linux@xxxxxxxxxx
>Cc: linux-kernel@xxxxxxxxxxxxxxx
>Cc: linux-hardening@xxxxxxxxxxxxxxx
>---
> init/Kconfig | 10 ++++
> kernel/.kunitconfig | 3 ++
> kernel/user_namespace.c | 4 ++
> kernel/user_namespace_kunit.c | 92 +++++++++++++++++++++++++++++++++++
> 4 files changed, 109 insertions(+)
> create mode 100644 kernel/.kunitconfig
> create mode 100644 kernel/user_namespace_kunit.c
>
>diff --git a/init/Kconfig b/init/Kconfig
>index f63bf5e05e79..d460344539a5 100644
>--- a/init/Kconfig
>+++ b/init/Kconfig
>@@ -1457,6 +1457,16 @@ config USER_NS
>
> If unsure, say N.
>
>+config USER_NAMESPACE_KUNIT_TEST
>+ bool "Test user namespace map insertion" if !KUNIT_ALL_TESTS
>+ depends on KUNIT=y
>+ default KUNIT_ALL_TESTS
>+ help
>+ This builds the KUnit test for user namespace uid/gid map insertion.
>+ It validates map insertion, limits, dynamic allocation of the
>+ extended extents array, and mapping sorting functions.
>+ If unsure, say N.
>+
> config PID_NS
> bool "PID Namespaces"
> default y
>diff --git a/kernel/.kunitconfig b/kernel/.kunitconfig
>new file mode 100644
>index 000000000000..7314dce05dc2
>--- /dev/null
>+++ b/kernel/.kunitconfig
>@@ -0,0 +1,3 @@
>+CONFIG_KUNIT=y
>+CONFIG_USER_NS=y
>+CONFIG_USER_NAMESPACE_KUNIT_TEST=y
>diff --git a/kernel/user_namespace.c b/kernel/user_namespace.c
>index 786dbf0506ca..0e7373085af9 100644
>--- a/kernel/user_namespace.c
>+++ b/kernel/user_namespace.c
>@@ -1417,3 +1417,7 @@ static __init int user_namespaces_init(void)
> return 0;
> }
> subsys_initcall(user_namespaces_init);
>+
>+#if IS_ENABLED(CONFIG_USER_NAMESPACE_KUNIT_TEST)
>+#include "user_namespace_kunit.c"
>+#endif
>diff --git a/kernel/user_namespace_kunit.c b/kernel/user_namespace_kunit.c
>new file mode 100644
>index 000000000000..88467361efdf
>--- /dev/null
>+++ b/kernel/user_namespace_kunit.c
>@@ -0,0 +1,92 @@
>+// SPDX-License-Identifier: GPL-2.0
>+/*
>+ * KUnit test for user namespace map insertion and sorting.
>+ */
>+
>+#include <kunit/test.h>
>+#include <linux/user_namespace.h>
>+
>+static void test_user_ns_map_insert_base(struct kunit *test)
>+{
>+ struct uid_gid_map map;
>+ struct uid_gid_extent extent;
>+ int i, ret;
>+
>+ memset(&map, 0, sizeof(map));
>+
>+ /* Insert up to UID_GID_MAP_MAX_BASE_EXTENTS (5) elements */
>+ for (i = 0; i < UID_GID_MAP_MAX_BASE_EXTENTS; i++) {
>+ extent.first = i * 10;
>+ extent.lower_first = i * 100;
>+ extent.count = 5;
>+
>+ ret = insert_extent(&map, &extent);
>+ KUNIT_ASSERT_EQ(test, ret, 0);
>+ KUNIT_EXPECT_EQ(test, map.nr_extents, i + 1);
>+ KUNIT_EXPECT_EQ(test, map.extent[i].first, i * 10);
>+ KUNIT_EXPECT_EQ(test, map.extent[i].lower_first, i * 100);
>+ KUNIT_EXPECT_EQ(test, map.extent[i].count, 5);
>+ }
>+}
>+
>+static void test_user_ns_map_insert_extended(struct kunit *test)
>+{
>+ struct uid_gid_map map;
>+ struct uid_gid_extent extent;
>+ int i, ret;
>+
>+ memset(&map, 0, sizeof(map));
>+
>+ /* Insert more than UID_GID_MAP_MAX_BASE_EXTENTS (e.g., 10) elements */
>+ for (i = 0; i < 10; i++) {
>+ int value = 9 - i;
>+
>+ extent.first = value * 10;
>+ extent.lower_first = value * 100;
>+ extent.count = 5;
>+
>+ ret = insert_extent(&map, &extent);
>+ KUNIT_ASSERT_EQ(test, ret, 0);
>+ KUNIT_EXPECT_EQ(test, map.nr_extents, i + 1);
>+
>+ if (i < UID_GID_MAP_MAX_BASE_EXTENTS) {
>+ KUNIT_EXPECT_EQ(test, map.extent[i].first, value * 10);
>+ } else {
>+ KUNIT_EXPECT_EQ(test, map.forward[i].first, value * 10);
>+ KUNIT_EXPECT_EQ(test, map.forward[i].lower_first, value * 100);
>+ KUNIT_EXPECT_EQ(test, map.forward[i].count, 5);
>+ }
>+ }
>+
>+ /* Now sort the map to set up reverse mapping */
>+ ret = sort_idmaps(&map);
>+ KUNIT_EXPECT_EQ(test, ret, 0);
>+ KUNIT_ASSERT_NOT_ERR_OR_NULL(test, map.reverse);
>+
>+ /* Verify sorting is correct */
>+ for (i = 0; i < map.nr_extents; i++) {
>+ KUNIT_EXPECT_EQ(test, map.forward[i].first, i * 10);
>+ KUNIT_EXPECT_EQ(test, map.forward[i].lower_first, i * 100);
>+ KUNIT_EXPECT_EQ(test, map.forward[i].count, 5);
>+
>+ KUNIT_EXPECT_EQ(test, map.reverse[i].first, i * 10);
>+ KUNIT_EXPECT_EQ(test, map.reverse[i].lower_first, i * 100);
>+ KUNIT_EXPECT_EQ(test, map.reverse[i].count, 5);
>+ }
>+
>+ kfree(map.forward);
>+ kfree(map.reverse);
>+}
>+
>+static struct kunit_case user_ns_map_test_cases[] = {
>+ KUNIT_CASE(test_user_ns_map_insert_base),
>+ KUNIT_CASE(test_user_ns_map_insert_extended),
>+ {}
>+};
>+
>+static struct kunit_suite user_ns_map_test_suite = {
>+ .name = "user_ns_map",
>+ .test_cases = user_ns_map_test_cases,
>+};
>+
>+kunit_test_suite(user_ns_map_test_suite);
>
--- Thanks!
https://lore.kernel.org/all/EE579805-42F2-4C58-B752-F28779EEB717@xxxxxxxxx/