[PATCH 1/2] kunit: test: Add vm_mmap() allocation resource manager

Kees Cook
2024-05-19T19:12:56Z

For tests that need to allocate using vm_mmap() (e.g. usercopy and
execve), provide the interface to have the allocation tracked by KUnit
itself. This requires bringing up a placeholder userspace mm.

This combines my earlier attempt at this with Mark Rutland's version[1].

Link: https://lore.kernel.org/lkml/20230321122514.1743889-2-mark.rutland@arm.com/ [1]
Co-developed-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Kees Cook <keescook@chromium.org>
---
include/kunit/test.h | 17 ++++++
lib/kunit/test.c | 139 ++++++++++++++++++++++++++++++++++++++++++-
2 files changed, 155 insertions(+), 1 deletion(-)

diff --git a/include/kunit/test.h b/include/kunit/test.h
index 61637ef32302..8c3835a6f282 100644
--- a/include/kunit/test.h
+++ b/include/kunit/test.h
@@ -478,6 +478,23 @@ 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_vm_mmap() - Allocate KUnit-tracked vm_mmap() area
+ * @test: The test context object.
+ * @file: struct file pointer to map from, if any
+ * @addr: desired address, if any
+ * @len: how many bytes to allocate
+ * @prot: mmap PROT_* bits
+ * @flag: mmap flags
+ * @offset: offset into @file to start mapping from.
+ *
+ * See vm_mmap() for more information.
+ */
+unsigned long kunit_vm_mmap(struct kunit *test, struct file *file,
+ unsigned long addr, unsigned long len,
+ unsigned long prot, unsigned long flag,
+ unsigned long offset);
+
void kunit_cleanup(struct kunit *test);

void __printf(2, 3) kunit_log_append(struct string_stream *log, const char *fmt, ...);
diff --git a/lib/kunit/test.c b/lib/kunit/test.c
index 1d1475578515..09194dbffb63 100644
--- a/lib/kunit/test.c
+++ b/lib/kunit/test.c
@@ -11,13 +11,14 @@
#include <kunit/test-bug.h>
#include <kunit/attributes.h>
#include <linux/kernel.h>
+#include <linux/kthread.h>
+#include <linux/mm.h>
#include <linux/module.h>
#include <linux/moduleparam.h>
#include <linux/mutex.h>
#include <linux/panic.h>
#include <linux/sched/debug.h>
#include <linux/sched.h>
-#include <linux/mm.h>

#include "debugfs.h"
#include "device-impl.h"
@@ -871,6 +872,142 @@ void kunit_kfree(struct kunit *test, const void *ptr)
}
EXPORT_SYMBOL_GPL(kunit_kfree);

+struct kunit_vm_mmap_resource {
+ unsigned long addr;
+ size_t size;
+};
+
+/* vm_mmap() arguments */
+struct kunit_vm_mmap_params {
+ struct file *file;
+ unsigned long addr;
+ unsigned long len;
+ unsigned long prot;
+ unsigned long flag;
+ unsigned long offset;
+};
+
+/*
+ * Arbitrarily chosen user address for the base allocation.
+ */
+#define UBUF_ADDR_BASE SZ_2M
+
+/* Create and attach a new mm if it doesn't already exist. */
+static int kunit_attach_mm(void)
+{
+ struct vm_area_struct *vma;
+ struct mm_struct *mm;
+
+ if (current->mm)
+ return 0;
+
+ mm = mm_alloc();
+ if (!mm)
+ return -ENOMEM;
+
+ if (mmap_write_lock_killable(mm))
+ goto out_free;
+
+ /* Define the task size. */
+ mm->task_size = TASK_SIZE;
+
+ /* Prepare the base VMA. */
+ vma = vm_area_alloc(mm);
+ if (!vma)
+ goto out_unlock;
+
+ vma_set_anonymous(vma);
+ vma->vm_start = UBUF_ADDR_BASE;
+ vma->vm_end = UBUF_ADDR_BASE + PAGE_SIZE;
+ vm_flags_init(vma, VM_READ | VM_MAYREAD | VM_WRITE | VM_MAYWRITE);
+ vma->vm_page_prot = vm_get_page_prot(vma->vm_flags);
+
+ if (insert_vm_struct(mm, vma))
+ goto out_free_vma;
+
+ mmap_write_unlock(mm);
+
+ /* Make sure we can allocate new VMAs. */
+ arch_pick_mmap_layout(mm, &current->signal->rlim[RLIMIT_STACK]);
+
+ /* Attach the mm. It will be cleaned up when the process dies. */
+ kthread_use_mm(mm);
+
+ return 0;
+
+out_free_vma:
+ vm_area_free(vma);
+out_unlock:
+ mmap_write_unlock(mm);
+out_free:
+ mmput(mm);
+ return -ENOMEM;
+}
+
+static int kunit_vm_mmap_init(struct kunit_resource *res, void *context)
+{
+ struct kunit_vm_mmap_params *p = context;
+ struct kunit_vm_mmap_resource vres;
+ int ret;
+
+ ret = kunit_attach_mm();
+ if (ret)
+ return ret;
+
+ vres.size = p->len;
+ vres.addr = vm_mmap(p->file, p->addr, p->len, p->prot, p->flag, p->offset);
+ if (!vres.addr)
+ return -ENOMEM;
+ res->data = kmemdup(&vres, sizeof(vres), GFP_KERNEL);
+ if (!res->data) {
+ vm_munmap(vres.addr, vres.size);
+ return -ENOMEM;
+ }
+
+ return 0;
+}
+
+static void kunit_vm_mmap_free(struct kunit_resource *res)
+{
+ struct kunit_vm_mmap_resource *vres = res->data;
+
+ /*
+ * Since this is executed from the test monitoring process,
+ * the test's mm has already been torn down. We don't need
+ * to run vm_munmap(vres->addr, vres->size), only clean up
+ * the vres.
+ */
+
+ kfree(vres);
+ res->data = NULL;
+}
+
+unsigned long kunit_vm_mmap(struct kunit *test, struct file *file,
+ unsigned long addr, unsigned long len,
+ unsigned long prot, unsigned long flag,
+ unsigned long offset)
+{
+ struct kunit_vm_mmap_params params = {
+ .file = file,
+ .addr = addr,
+ .len = len,
+ .prot = prot,
+ .flag = flag,
+ .offset = offset,
+ };
+ struct kunit_vm_mmap_resource *vres;
+
+ vres = kunit_alloc_resource(test,
+ kunit_vm_mmap_init,
+ kunit_vm_mmap_free,
+ GFP_KERNEL,
+ &params);
+ if (vres)
+ return vres->addr;
+ return 0;
+}
+EXPORT_SYMBOL_GPL(kunit_vm_mmap);
+
void kunit_cleanup(struct kunit *test)
{
struct kunit_resource *res;
--
2.34.1