49ee4dd2e7
Add proper error handling when allocating or getting shadow variables in the selftest. It prevents an invalid pointer access in some situations. It shows the good programming practice in the others. The error codes are just the best guess and specific for this particular test. In general, klp_shadow_alloc() returns NULL also when the given shadow variable has already been allocated. In addition, both klp_shadow_alloc() and klp_shadow_get_or_alloc() might fail from other reasons when the constructor fails. Note, that the error code is not really important even in the real life. The use of shadow variables should be transparent for the original livepatched code. Acked-by: Miroslav Benes <mbenes@suse.cz> Acked-by: Joe Lawrence <joe.lawrence@redhat.com> Signed-off-by: Petr Mladek <pmladek@suse.com>
259 lines
6.3 KiB
C
259 lines
6.3 KiB
C
// SPDX-License-Identifier: GPL-2.0
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// Copyright (C) 2018 Joe Lawrence <joe.lawrence@redhat.com>
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#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
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#include <linux/module.h>
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#include <linux/kernel.h>
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#include <linux/list.h>
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#include <linux/livepatch.h>
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#include <linux/slab.h>
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/*
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* Keep a small list of pointers so that we can print address-agnostic
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* pointer values. Use a rolling integer count to differentiate the values.
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* Ironically we could have used the shadow variable API to do this, but
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* let's not lean too heavily on the very code we're testing.
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*/
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static LIST_HEAD(ptr_list);
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struct shadow_ptr {
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void *ptr;
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int id;
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struct list_head list;
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};
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static void free_ptr_list(void)
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{
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struct shadow_ptr *sp, *tmp_sp;
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list_for_each_entry_safe(sp, tmp_sp, &ptr_list, list) {
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list_del(&sp->list);
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kfree(sp);
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}
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}
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static int ptr_id(void *ptr)
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{
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struct shadow_ptr *sp;
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static int count;
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list_for_each_entry(sp, &ptr_list, list) {
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if (sp->ptr == ptr)
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return sp->id;
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}
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sp = kmalloc(sizeof(*sp), GFP_ATOMIC);
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if (!sp)
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return -ENOMEM;
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sp->ptr = ptr;
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sp->id = count++;
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list_add(&sp->list, &ptr_list);
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return sp->id;
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}
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/*
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* Shadow variable wrapper functions that echo the function and arguments
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* to the kernel log for testing verification. Don't display raw pointers,
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* but use the ptr_id() value instead.
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*/
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static void *shadow_get(void *obj, unsigned long id)
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{
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void *ret = klp_shadow_get(obj, id);
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pr_info("klp_%s(obj=PTR%d, id=0x%lx) = PTR%d\n",
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__func__, ptr_id(obj), id, ptr_id(ret));
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return ret;
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}
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static void *shadow_alloc(void *obj, unsigned long id, size_t size,
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gfp_t gfp_flags, klp_shadow_ctor_t ctor,
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void *ctor_data)
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{
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void *ret = klp_shadow_alloc(obj, id, size, gfp_flags, ctor,
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ctor_data);
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pr_info("klp_%s(obj=PTR%d, id=0x%lx, size=%zx, gfp_flags=%pGg), ctor=PTR%d, ctor_data=PTR%d = PTR%d\n",
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__func__, ptr_id(obj), id, size, &gfp_flags, ptr_id(ctor),
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ptr_id(ctor_data), ptr_id(ret));
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return ret;
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}
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static void *shadow_get_or_alloc(void *obj, unsigned long id, size_t size,
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gfp_t gfp_flags, klp_shadow_ctor_t ctor,
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void *ctor_data)
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{
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void *ret = klp_shadow_get_or_alloc(obj, id, size, gfp_flags, ctor,
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ctor_data);
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pr_info("klp_%s(obj=PTR%d, id=0x%lx, size=%zx, gfp_flags=%pGg), ctor=PTR%d, ctor_data=PTR%d = PTR%d\n",
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__func__, ptr_id(obj), id, size, &gfp_flags, ptr_id(ctor),
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ptr_id(ctor_data), ptr_id(ret));
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return ret;
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}
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static void shadow_free(void *obj, unsigned long id, klp_shadow_dtor_t dtor)
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{
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klp_shadow_free(obj, id, dtor);
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pr_info("klp_%s(obj=PTR%d, id=0x%lx, dtor=PTR%d)\n",
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__func__, ptr_id(obj), id, ptr_id(dtor));
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}
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static void shadow_free_all(unsigned long id, klp_shadow_dtor_t dtor)
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{
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klp_shadow_free_all(id, dtor);
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pr_info("klp_%s(id=0x%lx, dtor=PTR%d)\n",
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__func__, id, ptr_id(dtor));
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}
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/* Shadow variable constructor - remember simple pointer data */
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static int shadow_ctor(void *obj, void *shadow_data, void *ctor_data)
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{
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int **shadow_int = shadow_data;
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*shadow_int = ctor_data;
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pr_info("%s: PTR%d -> PTR%d\n",
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__func__, ptr_id(shadow_int), ptr_id(ctor_data));
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return 0;
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}
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static void shadow_dtor(void *obj, void *shadow_data)
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{
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pr_info("%s(obj=PTR%d, shadow_data=PTR%d)\n",
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__func__, ptr_id(obj), ptr_id(shadow_data));
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}
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static int test_klp_shadow_vars_init(void)
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{
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void *obj = THIS_MODULE;
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int id = 0x1234;
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size_t size = sizeof(int *);
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gfp_t gfp_flags = GFP_KERNEL;
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int var1, var2, var3, var4;
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int **sv1, **sv2, **sv3, **sv4;
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void *ret;
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ptr_id(NULL);
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ptr_id(&var1);
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ptr_id(&var2);
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ptr_id(&var3);
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ptr_id(&var4);
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/*
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* With an empty shadow variable hash table, expect not to find
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* any matches.
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*/
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ret = shadow_get(obj, id);
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if (!ret)
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pr_info(" got expected NULL result\n");
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/*
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* Allocate a few shadow variables with different <obj> and <id>.
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*/
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sv1 = shadow_alloc(obj, id, size, gfp_flags, shadow_ctor, &var1);
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if (!sv1)
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return -ENOMEM;
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sv2 = shadow_alloc(obj + 1, id, size, gfp_flags, shadow_ctor, &var2);
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if (!sv2)
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return -ENOMEM;
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sv3 = shadow_alloc(obj, id + 1, size, gfp_flags, shadow_ctor, &var3);
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if (!sv3)
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return -ENOMEM;
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/*
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* Verify we can find our new shadow variables and that they point
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* to expected data.
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*/
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ret = shadow_get(obj, id);
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if (!ret)
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return -EINVAL;
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if (ret == sv1 && *sv1 == &var1)
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pr_info(" got expected PTR%d -> PTR%d result\n",
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ptr_id(sv1), ptr_id(*sv1));
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ret = shadow_get(obj + 1, id);
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if (!ret)
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return -EINVAL;
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if (ret == sv2 && *sv2 == &var2)
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pr_info(" got expected PTR%d -> PTR%d result\n",
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ptr_id(sv2), ptr_id(*sv2));
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ret = shadow_get(obj, id + 1);
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if (!ret)
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return -EINVAL;
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if (ret == sv3 && *sv3 == &var3)
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pr_info(" got expected PTR%d -> PTR%d result\n",
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ptr_id(sv3), ptr_id(*sv3));
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/*
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* Allocate or get a few more, this time with the same <obj>, <id>.
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* The second invocation should return the same shadow var.
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*/
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sv4 = shadow_get_or_alloc(obj + 2, id, size, gfp_flags, shadow_ctor, &var4);
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if (!sv4)
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return -ENOMEM;
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ret = shadow_get_or_alloc(obj + 2, id, size, gfp_flags, shadow_ctor, &var4);
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if (!ret)
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return -EINVAL;
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if (ret == sv4 && *sv4 == &var4)
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pr_info(" got expected PTR%d -> PTR%d result\n",
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ptr_id(sv4), ptr_id(*sv4));
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/*
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* Free the <obj=*, id> shadow variables and check that we can no
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* longer find them.
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*/
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shadow_free(obj, id, shadow_dtor); /* sv1 */
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ret = shadow_get(obj, id);
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if (!ret)
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pr_info(" got expected NULL result\n");
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shadow_free(obj + 1, id, shadow_dtor); /* sv2 */
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ret = shadow_get(obj + 1, id);
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if (!ret)
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pr_info(" got expected NULL result\n");
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shadow_free(obj + 2, id, shadow_dtor); /* sv4 */
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ret = shadow_get(obj + 2, id);
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if (!ret)
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pr_info(" got expected NULL result\n");
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/*
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* We should still find an <id+1> variable.
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*/
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ret = shadow_get(obj, id + 1);
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if (!ret)
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return -EINVAL;
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if (ret == sv3 && *sv3 == &var3)
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pr_info(" got expected PTR%d -> PTR%d result\n",
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ptr_id(sv3), ptr_id(*sv3));
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/*
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* Free all the <id+1> variables, too.
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*/
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shadow_free_all(id + 1, shadow_dtor); /* sv3 */
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ret = shadow_get(obj, id);
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if (!ret)
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pr_info(" shadow_get() got expected NULL result\n");
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free_ptr_list();
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return 0;
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}
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static void test_klp_shadow_vars_exit(void)
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{
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}
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module_init(test_klp_shadow_vars_init);
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module_exit(test_klp_shadow_vars_exit);
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MODULE_LICENSE("GPL");
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MODULE_AUTHOR("Joe Lawrence <joe.lawrence@redhat.com>");
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MODULE_DESCRIPTION("Livepatch test: shadow variables");
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