273 lines
6.5 KiB
C
273 lines
6.5 KiB
C
// SPDX-License-Identifier: GPL-2.0
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/*
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* This is for all the tests related to validating kernel memory
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* permissions: non-executable regions, non-writable regions, and
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* even non-readable regions.
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*/
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#include "lkdtm.h"
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#include <linux/slab.h>
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#include <linux/vmalloc.h>
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#include <linux/mman.h>
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#include <linux/uaccess.h>
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#include <asm/cacheflush.h>
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#include <asm/sections.h>
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/* Whether or not to fill the target memory area with do_nothing(). */
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#define CODE_WRITE true
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#define CODE_AS_IS false
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/* How many bytes to copy to be sure we've copied enough of do_nothing(). */
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#define EXEC_SIZE 64
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/* This is non-const, so it will end up in the .data section. */
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static u8 data_area[EXEC_SIZE];
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/* This is const, so it will end up in the .rodata section. */
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static const unsigned long rodata = 0xAA55AA55;
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/* This is marked __ro_after_init, so it should ultimately be .rodata. */
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static unsigned long ro_after_init __ro_after_init = 0x55AA5500;
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/*
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* This just returns to the caller. It is designed to be copied into
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* non-executable memory regions.
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*/
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static noinline void do_nothing(void)
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{
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return;
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}
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/* Must immediately follow do_nothing for size calculuations to work out. */
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static noinline void do_overwritten(void)
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{
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pr_info("do_overwritten wasn't overwritten!\n");
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return;
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}
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static noinline void do_almost_nothing(void)
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{
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pr_info("do_nothing was hijacked!\n");
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}
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static void *setup_function_descriptor(func_desc_t *fdesc, void *dst)
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{
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if (!have_function_descriptors())
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return dst;
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memcpy(fdesc, do_nothing, sizeof(*fdesc));
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fdesc->addr = (unsigned long)dst;
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barrier();
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return fdesc;
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}
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static noinline void execute_location(void *dst, bool write)
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{
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void (*func)(void);
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func_desc_t fdesc;
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void *do_nothing_text = dereference_function_descriptor(do_nothing);
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pr_info("attempting ok execution at %px\n", do_nothing_text);
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do_nothing();
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if (write == CODE_WRITE) {
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memcpy(dst, do_nothing_text, EXEC_SIZE);
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flush_icache_range((unsigned long)dst,
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(unsigned long)dst + EXEC_SIZE);
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}
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pr_info("attempting bad execution at %px\n", dst);
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func = setup_function_descriptor(&fdesc, dst);
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func();
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pr_err("FAIL: func returned\n");
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}
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static void execute_user_location(void *dst)
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{
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int copied;
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/* Intentionally crossing kernel/user memory boundary. */
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void (*func)(void);
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func_desc_t fdesc;
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void *do_nothing_text = dereference_function_descriptor(do_nothing);
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pr_info("attempting ok execution at %px\n", do_nothing_text);
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do_nothing();
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copied = access_process_vm(current, (unsigned long)dst, do_nothing_text,
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EXEC_SIZE, FOLL_WRITE);
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if (copied < EXEC_SIZE)
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return;
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pr_info("attempting bad execution at %px\n", dst);
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func = setup_function_descriptor(&fdesc, dst);
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func();
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pr_err("FAIL: func returned\n");
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}
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void lkdtm_WRITE_RO(void)
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{
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/* Explicitly cast away "const" for the test and make volatile. */
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volatile unsigned long *ptr = (unsigned long *)&rodata;
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pr_info("attempting bad rodata write at %px\n", ptr);
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*ptr ^= 0xabcd1234;
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pr_err("FAIL: survived bad write\n");
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}
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void lkdtm_WRITE_RO_AFTER_INIT(void)
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{
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volatile unsigned long *ptr = &ro_after_init;
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/*
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* Verify we were written to during init. Since an Oops
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* is considered a "success", a failure is to just skip the
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* real test.
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*/
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if ((*ptr & 0xAA) != 0xAA) {
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pr_info("%p was NOT written during init!?\n", ptr);
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return;
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}
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pr_info("attempting bad ro_after_init write at %px\n", ptr);
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*ptr ^= 0xabcd1234;
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pr_err("FAIL: survived bad write\n");
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}
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void lkdtm_WRITE_KERN(void)
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{
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size_t size;
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volatile unsigned char *ptr;
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size = (unsigned long)dereference_function_descriptor(do_overwritten) -
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(unsigned long)dereference_function_descriptor(do_nothing);
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ptr = dereference_function_descriptor(do_overwritten);
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pr_info("attempting bad %zu byte write at %px\n", size, ptr);
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memcpy((void *)ptr, (unsigned char *)do_nothing, size);
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flush_icache_range((unsigned long)ptr, (unsigned long)(ptr + size));
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pr_err("FAIL: survived bad write\n");
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do_overwritten();
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}
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void lkdtm_WRITE_OPD(void)
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{
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size_t size = sizeof(func_desc_t);
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void (*func)(void) = do_nothing;
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if (!have_function_descriptors()) {
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pr_info("XFAIL: Platform doesn't use function descriptors.\n");
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return;
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}
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pr_info("attempting bad %zu bytes write at %px\n", size, do_nothing);
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memcpy(do_nothing, do_almost_nothing, size);
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pr_err("FAIL: survived bad write\n");
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asm("" : "=m"(func));
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func();
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}
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void lkdtm_EXEC_DATA(void)
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{
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execute_location(data_area, CODE_WRITE);
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}
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void lkdtm_EXEC_STACK(void)
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{
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u8 stack_area[EXEC_SIZE];
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execute_location(stack_area, CODE_WRITE);
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}
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void lkdtm_EXEC_KMALLOC(void)
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{
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u32 *kmalloc_area = kmalloc(EXEC_SIZE, GFP_KERNEL);
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execute_location(kmalloc_area, CODE_WRITE);
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kfree(kmalloc_area);
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}
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void lkdtm_EXEC_VMALLOC(void)
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{
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u32 *vmalloc_area = vmalloc(EXEC_SIZE);
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execute_location(vmalloc_area, CODE_WRITE);
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vfree(vmalloc_area);
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}
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void lkdtm_EXEC_RODATA(void)
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{
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execute_location(dereference_function_descriptor(lkdtm_rodata_do_nothing),
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CODE_AS_IS);
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}
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void lkdtm_EXEC_USERSPACE(void)
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{
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unsigned long user_addr;
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user_addr = vm_mmap(NULL, 0, PAGE_SIZE,
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PROT_READ | PROT_WRITE | PROT_EXEC,
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MAP_ANONYMOUS | MAP_PRIVATE, 0);
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if (user_addr >= TASK_SIZE) {
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pr_warn("Failed to allocate user memory\n");
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return;
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}
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execute_user_location((void *)user_addr);
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vm_munmap(user_addr, PAGE_SIZE);
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}
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void lkdtm_EXEC_NULL(void)
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{
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execute_location(NULL, CODE_AS_IS);
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}
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void lkdtm_ACCESS_USERSPACE(void)
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{
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unsigned long user_addr, tmp = 0;
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unsigned long *ptr;
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user_addr = vm_mmap(NULL, 0, PAGE_SIZE,
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PROT_READ | PROT_WRITE | PROT_EXEC,
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MAP_ANONYMOUS | MAP_PRIVATE, 0);
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if (user_addr >= TASK_SIZE) {
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pr_warn("Failed to allocate user memory\n");
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return;
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}
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if (copy_to_user((void __user *)user_addr, &tmp, sizeof(tmp))) {
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pr_warn("copy_to_user failed\n");
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vm_munmap(user_addr, PAGE_SIZE);
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return;
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}
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ptr = (unsigned long *)user_addr;
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pr_info("attempting bad read at %px\n", ptr);
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tmp = *ptr;
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tmp += 0xc0dec0de;
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pr_err("FAIL: survived bad read\n");
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pr_info("attempting bad write at %px\n", ptr);
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*ptr = tmp;
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pr_err("FAIL: survived bad write\n");
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vm_munmap(user_addr, PAGE_SIZE);
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}
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void lkdtm_ACCESS_NULL(void)
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{
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unsigned long tmp;
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volatile unsigned long *ptr = (unsigned long *)NULL;
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pr_info("attempting bad read at %px\n", ptr);
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tmp = *ptr;
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tmp += 0xc0dec0de;
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pr_err("FAIL: survived bad read\n");
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pr_info("attempting bad write at %px\n", ptr);
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*ptr = tmp;
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pr_err("FAIL: survived bad write\n");
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}
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void __init lkdtm_perms_init(void)
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{
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/* Make sure we can write to __ro_after_init values during __init */
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ro_after_init |= 0xAA;
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}
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