From f2c6dbd220170c2396fb019ead67fbada1e23ebd Mon Sep 17 00:00:00 2001 From: David Gow Date: Fri, 16 Aug 2024 12:51:22 +0800 Subject: [PATCH] kunit: Device wrappers should also manage driver name 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. However, these are inline functions, and is_kernel_rodata() only works for built-in code. This causes problems in two cases: - If kunit is built as a module, __{start,end}_rodata is not defined. - If a kunit test using these functions is built as a module, it will suffer the same fate. This fixes a KASAN splat with overflow.overflow_allocation_test, when built as a module. Restrict the is_kernel_rodata() case to when KUnit is built as a module, which fixes the first case, at the cost of losing the optimisation. Also, make kunit_{kstrdup,kfree}_const non-inline, so that other modules using them will not accidentally depend on is_kernel_rodata(). If KUnit is built-in, they'll benefit from the optimisation, if KUnit is not, they won't, but the string will be properly duplicated. Fixes: d03c720e03bd ("kunit: Add APIs for managing devices") Reported-by: Nico Pache Closes: https://groups.google.com/g/kunit-dev/c/81V9b9QYON0 Reviewed-by: Kees Cook Reviewed-by: Maxime Ripard Reviewed-by: Rae Moar Signed-off-by: David Gow Tested-by: Rae Moar Signed-off-by: Shuah Khan --- include/kunit/test.h | 48 ++++++++++++++++++++++++++++++++++++++++++++ lib/kunit/device.c | 7 +++++-- lib/kunit/test.c | 19 ++++++++++++++++++ 3 files changed, 72 insertions(+), 2 deletions(-) diff --git a/include/kunit/test.h b/include/kunit/test.h index e2a1f0928e8b..5ac237c949a0 100644 --- a/include/kunit/test.h +++ b/include/kunit/test.h @@ -28,6 +28,7 @@ #include #include +#include /* Static key: true if any KUnit tests are currently running */ DECLARE_STATIC_KEY_FALSE(kunit_running); @@ -480,6 +481,53 @@ 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. + */ +void kunit_kfree_const(struct kunit *test, const void *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_kfree_const() -- not kunit_kfree(). + * See kstrdup_const() and kunit_kmalloc_array() for more information. + */ +const char *kunit_kstrdup_const(struct kunit *test, const char *str, gfp_t 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); diff --git a/lib/kunit/test.c b/lib/kunit/test.c index e8b1b52a19ab..089c832e3cdb 100644 --- a/lib/kunit/test.c +++ b/lib/kunit/test.c @@ -874,6 +874,25 @@ void kunit_kfree(struct kunit *test, const void *ptr) } EXPORT_SYMBOL_GPL(kunit_kfree); +void kunit_kfree_const(struct kunit *test, const void *x) +{ +#if !IS_MODULE(CONFIG_KUNIT) + if (!is_kernel_rodata((unsigned long)x)) +#endif + kunit_kfree(test, x); +} +EXPORT_SYMBOL_GPL(kunit_kfree_const); + +const char *kunit_kstrdup_const(struct kunit *test, const char *str, gfp_t gfp) +{ +#if !IS_MODULE(CONFIG_KUNIT) + if (is_kernel_rodata((unsigned long)str)) + return str; +#endif + return kunit_kstrdup(test, str, gfp); +} +EXPORT_SYMBOL_GPL(kunit_kstrdup_const); + void kunit_cleanup(struct kunit *test) { struct kunit_resource *res;