On Thu, Aug 27, 2026 at 6:37 AM Thomas Weißschuh
<[email protected]> wrote:
>
> On Wed, Aug 26, 2026 at 10:00:35PM +0000, Bill Wendling 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
> > Signed-off-by: Bill Wendling <[email protected]>
> > ---
> > 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 <[email protected]>
> > Cc: Thomas Weißschuh <[email protected]>
> > Cc: Kees Cook <[email protected]>
> > Cc: "Gustavo A. R. Silva" <[email protected]>
> > Cc: Christian Brauner <[email protected]>
> > Cc: Aleksa Sarai <[email protected]>
> > Cc: Jan Kara <[email protected]>
> > Cc: Nathan Chancellor <[email protected]>
> > Cc: Miguel Ojeda <[email protected]>
> > Cc: Thomas Gleixner <[email protected]>
> > Cc: Nicolas Schier <[email protected]>
> > Cc: Gary Guo <[email protected]>
> > Cc: "Thomas Weißschuh" <[email protected]>
> > Cc: Alice Ryhl <[email protected]>
> > Cc: Douglas Anderson <[email protected]>
> > Cc: Anand Moon <[email protected]>
> > Cc: Oleg Nesterov <[email protected]>
> > Cc: [email protected]
> > Cc: [email protected]
> > Cc: [email protected]
> > ---
> > 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
>
> Urgh.
>
?? What's wrong? It's identical to the conditional for EXEC_KUNIT_TEST:
config EXEC_KUNIT_TEST
bool "Build execve tests" if !KUNIT_ALL_TESTS
depends on KUNIT=y
default KUNIT_ALL_TESTS
help
This builds the exec KUnit tests, which tests boundary conditions
of various aspects of the exec internals.
> > + 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);
> > + }
> > +}
>
> The extended test below already tests everything the 'base' one does.
> Do we need both?
>
The one below tests the sorting algorithm.
> > +
> > +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
> > */
>
> When UID_GID_MAP_MAX_BASE_EXTENTS is ever increased, this might not be true
> anymore.
> Add an assertion or make the iteration count dynamic.
>
Sure, I can make it something like "UID_GID_MAP_MAX_BASE_EXTENTS + 42"
or something. Let me know about the "Urgh" comment above first.
> > + 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);
> > + }
>
> Isn't this the same as the original order?
>
No. The original order uses "9 - i" for the base value, so it's not in
sorted order (though it's not exactly random either).
-bw
> > +
> > + kfree(map.forward);
> > + kfree(map.reverse);
> > +}
>
> (...)
