On Wed, Jul 31, 2024 at 3:02 AM David Gow <davidgow@xxxxxxxxxx> wrote:
>
> kunit_driver_create() accepts a name for the driver, but does not copy
> it, so if that name is either on the stack, or otherwise freed, we end
> up with a use-after-free when the driver is cleaned up.
>
> Instead, strdup() the name, and manage it as another KUnit allocation.
> As there was no existing kunit_kstrdup(), we add one. Further, add a
> kunit_ variant of strdup_const() and kfree_const(), so we don't need to
> allocate and manage the string in the majority of cases where it's a
> constant.
>
> This fixes a KASAN splat with overflow.overflow_allocation_test, when
> built as a module.
>
> Fixes: d03c720e03bd ("kunit: Add APIs for managing devices")
> Reported-by: Nico Pache <npache@xxxxxxxxxx>
> Closes: https://groups.google.com/g/kunit-dev/c/81V9b9QYON0
> Signed-off-by: David Gow <davidgow@xxxxxxxxxx>
> Reviewed-by: Kees Cook <kees@xxxxxxxxxx>
> ---
>
> There's some more serious changes since the RFC I sent, so please take a
> closer look.
>
> Thanks,
> -- David
>
Hello!
These changes look good to me. Fun patch to review! Only comment is
that we could potentially add tests for these functions in a future
patch.
Reviewed-by: Rae Moar <rmoar@xxxxxxxxxx>
Thanks!
-Rae
> Changes since RFC:
> https://groups.google.com/g/kunit-dev/c/81V9b9QYON0/m/PFKNKDKAAAAJ
> - Add and use the kunit_kstrdup_const() and kunit_free_const()
> functions.
> - Fix a typo in the doc comments.
>
>
> ---
> include/kunit/test.h | 58 ++++++++++++++++++++++++++++++++++++++++++++
> lib/kunit/device.c | 7 ++++--
> 2 files changed, 63 insertions(+), 2 deletions(-)
>
> diff --git a/include/kunit/test.h b/include/kunit/test.h
> index e2a1f0928e8b..da9e84de14c0 100644
> --- a/include/kunit/test.h
> +++ b/include/kunit/test.h
> @@ -28,6 +28,7 @@
> #include <linux/types.h>
>
> #include <asm/rwonce.h>
> +#include <asm/sections.h>
>
> /* Static key: true if any KUnit tests are currently running */
> DECLARE_STATIC_KEY_FALSE(kunit_running);
> @@ -480,6 +481,63 @@ static inline void *kunit_kcalloc(struct kunit *test, size_t n, size_t size, gfp
> return kunit_kmalloc_array(test, n, size, gfp | __GFP_ZERO);
> }
>
> +
> +/**
> + * kunit_kfree_const() - conditionally free test managed memory
> + * @x: pointer to the memory
> + *
> + * Calls kunit_kfree() only if @x is not in .rodata section.
> + * See kunit_kstrdup_const() for more information.
> + */
> +static inline void kunit_kfree_const(struct kunit *test, const void *x)
> +{
> + if (!is_kernel_rodata((unsigned long)x))
> + kunit_kfree(test, x);
> +}
> +
> +/**
> + * kunit_kstrdup() - Duplicates a string into a test managed allocation.
> + *
> + * @test: The test context object.
> + * @str: The NULL-terminated string to duplicate.
> + * @gfp: flags passed to underlying kmalloc().
> + *
> + * See kstrdup() and kunit_kmalloc_array() for more information.
> + */
> +static inline char *kunit_kstrdup(struct kunit *test, const char *str, gfp_t gfp)
> +{
> + size_t len;
> + char *buf;
> +
> + if (!str)
> + return NULL;
> +
> + len = strlen(str) + 1;
> + buf = kunit_kmalloc(test, len, gfp);
> + if (buf)
> + memcpy(buf, str, len);
> + return buf;
> +}
> +
> +/**
> + * kunit_kstrdup_const() - Conditionally duplicates a string into a test managed allocation.
> + *
> + * @test: The test context object.
> + * @str: The NULL-terminated string to duplicate.
> + * @gfp: flags passed to underlying kmalloc().
> + *
> + * Calls kunit_kstrdup() only if @str is not in the rodata section. Must be freed with
> + * kunit_free_const() -- not kunit_free().
> + * See kstrdup_const() and kunit_kmalloc_array() for more information.
> + */
> +static inline const char *kunit_kstrdup_const(struct kunit *test, const char *str, gfp_t gfp)
> +{
> + if (is_kernel_rodata((unsigned long)str))
> + return str;
> +
> + return kunit_kstrdup(test, str, gfp);
> +}
> +
> /**
> * kunit_vm_mmap() - Allocate KUnit-tracked vm_mmap() area
> * @test: The test context object.
> diff --git a/lib/kunit/device.c b/lib/kunit/device.c
> index 25c81ed465fb..520c1fccee8a 100644
> --- a/lib/kunit/device.c
> +++ b/lib/kunit/device.c
> @@ -89,7 +89,7 @@ struct device_driver *kunit_driver_create(struct kunit *test, const char *name)
> if (!driver)
> return ERR_PTR(err);
>
> - driver->name = name;
> + driver->name = kunit_kstrdup_const(test, name, GFP_KERNEL);
> driver->bus = &kunit_bus_type;
> driver->owner = THIS_MODULE;
>
> @@ -192,8 +192,11 @@ void kunit_device_unregister(struct kunit *test, struct device *dev)
> const struct device_driver *driver = to_kunit_device(dev)->driver;
>
> kunit_release_action(test, device_unregister_wrapper, dev);
> - if (driver)
> + if (driver) {
> + const char *driver_name = driver->name;
> kunit_release_action(test, driver_unregister_wrapper, (void *)driver);
> + kunit_kfree_const(test, driver_name);
> + }
> }
> EXPORT_SYMBOL_GPL(kunit_device_unregister);
>
> --
> 2.46.0.rc1.232.g9752f9e123-goog
>
