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// SPDX-License-Identifier: GPL-2.0-only
/*
* Copyright 2022 Google LLC.
* Author: Suren Baghdasaryan <surenb@google.com>
*
* Permission to use, copy, modify, and distribute this software for any
* purpose with or without fee is hereby granted, provided that the above
* copyright notice and this permission notice appear in all copies.
*
* THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
* WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
* MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
* ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
* WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
* ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
* OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
*/
/*
* Fork a child that concurrently modifies address space while the main
* process is reading /proc/$PID/maps and verifying the results. Address
* space modifications include:
* VMA splitting and merging
*
*/
#define _GNU_SOURCE
#include "../kselftest_harness.h"
#include <errno.h>
#include <fcntl.h>
#include <pthread.h>
#include <stdbool.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <sys/mman.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <sys/wait.h>
/* /proc/pid/maps parsing routines */
struct page_content {
char *data;
ssize_t size;
};
#define LINE_MAX_SIZE 256
struct line_content {
char text[LINE_MAX_SIZE];
unsigned long start_addr;
unsigned long end_addr;
};
enum test_state {
INIT,
CHILD_READY,
PARENT_READY,
SETUP_READY,
SETUP_MODIFY_MAPS,
SETUP_MAPS_MODIFIED,
SETUP_RESTORE_MAPS,
SETUP_MAPS_RESTORED,
TEST_READY,
TEST_DONE,
};
struct vma_modifier_info;
FIXTURE(proc_maps_race)
{
struct vma_modifier_info *mod_info;
struct page_content page1;
struct page_content page2;
struct line_content last_line;
struct line_content first_line;
unsigned long duration_sec;
int shared_mem_size;
int page_size;
int vma_count;
bool verbose;
int maps_fd;
pid_t pid;
};
typedef bool (*vma_modifier_op)(FIXTURE_DATA(proc_maps_race) *self);
typedef bool (*vma_mod_result_check_op)(struct line_content *mod_last_line,
struct line_content *mod_first_line,
struct line_content *restored_last_line,
struct line_content *restored_first_line);
struct vma_modifier_info {
int vma_count;
void *addr;
int prot;
void *next_addr;
vma_modifier_op vma_modify;
vma_modifier_op vma_restore;
vma_mod_result_check_op vma_mod_check;
pthread_mutex_t sync_lock;
pthread_cond_t sync_cond;
enum test_state curr_state;
bool exit;
void *child_mapped_addr[];
};
static bool read_two_pages(FIXTURE_DATA(proc_maps_race) *self)
{
ssize_t bytes_read;
if (lseek(self->maps_fd, 0, SEEK_SET) < 0)
return false;
bytes_read = read(self->maps_fd, self->page1.data, self->page_size);
if (bytes_read <= 0)
return false;
self->page1.size = bytes_read;
bytes_read = read(self->maps_fd, self->page2.data, self->page_size);
if (bytes_read <= 0)
return false;
self->page2.size = bytes_read;
return true;
}
static void copy_first_line(struct page_content *page, char *first_line)
{
char *pos = strchr(page->data, '\n');
strncpy(first_line, page->data, pos - page->data);
first_line[pos - page->data] = '\0';
}
static void copy_last_line(struct page_content *page, char *last_line)
{
/* Get the last line in the first page */
const char *end = page->data + page->size - 1;
/* skip last newline */
const char *pos = end - 1;
/* search previous newline */
while (pos[-1] != '\n')
pos--;
strncpy(last_line, pos, end - pos);
last_line[end - pos] = '\0';
}
/* Read the last line of the first page and the first line of the second page */
static bool read_boundary_lines(FIXTURE_DATA(proc_maps_race) *self,
struct line_content *last_line,
struct line_content *first_line)
{
if (!read_two_pages(self))
return false;
copy_last_line(&self->page1, last_line->text);
copy_first_line(&self->page2, first_line->text);
return sscanf(last_line->text, "%lx-%lx", &last_line->start_addr,
&last_line->end_addr) == 2 &&
sscanf(first_line->text, "%lx-%lx", &first_line->start_addr,
&first_line->end_addr) == 2;
}
/* Thread synchronization routines */
static void wait_for_state(struct vma_modifier_info *mod_info, enum test_state state)
{
pthread_mutex_lock(&mod_info->sync_lock);
while (mod_info->curr_state != state)
pthread_cond_wait(&mod_info->sync_cond, &mod_info->sync_lock);
pthread_mutex_unlock(&mod_info->sync_lock);
}
static void signal_state(struct vma_modifier_info *mod_info, enum test_state state)
{
pthread_mutex_lock(&mod_info->sync_lock);
mod_info->curr_state = state;
pthread_cond_signal(&mod_info->sync_cond);
pthread_mutex_unlock(&mod_info->sync_lock);
}
static void stop_vma_modifier(struct vma_modifier_info *mod_info)
{
wait_for_state(mod_info, SETUP_READY);
mod_info->exit = true;
signal_state(mod_info, SETUP_MODIFY_MAPS);
}
static void print_first_lines(char *text, int nr)
{
const char *end = text;
while (nr && (end = strchr(end, '\n')) != NULL) {
nr--;
end++;
}
if (end) {
int offs = end - text;
text[offs] = '\0';
printf("%s", text);
text[offs] = '\n';
printf("\n");
} else {
printf("%s", text);
}
}
static void print_last_lines(char *text, int nr)
{
const char *start = text + strlen(text);
nr++; /* to ignore the last newline */
while (nr) {
while (start > text && *start != '\n')
start--;
nr--;
start--;
}
printf("%s", start);
}
static void print_boundaries(const char *title, FIXTURE_DATA(proc_maps_race) *self)
{
if (!self->verbose)
return;
printf("%s", title);
/* Print 3 boundary lines from each page */
print_last_lines(self->page1.data, 3);
printf("-----------------page boundary-----------------\n");
print_first_lines(self->page2.data, 3);
}
static bool print_boundaries_on(bool condition, const char *title,
FIXTURE_DATA(proc_maps_race) *self)
{
if (self->verbose && condition)
print_boundaries(title, self);
return condition;
}
static void report_test_start(const char *name, bool verbose)
{
if (verbose)
printf("==== %s ====\n", name);
}
static struct timespec print_ts;
static void start_test_loop(struct timespec *ts, bool verbose)
{
if (verbose)
print_ts.tv_sec = ts->tv_sec;
}
static void end_test_iteration(struct timespec *ts, bool verbose)
{
if (!verbose)
return;
/* Update every second */
if (print_ts.tv_sec == ts->tv_sec)
return;
printf(".");
fflush(stdout);
print_ts.tv_sec = ts->tv_sec;
}
static void end_test_loop(bool verbose)
{
if (verbose)
printf("\n");
}
static bool capture_mod_pattern(FIXTURE_DATA(proc_maps_race) *self,
struct line_content *mod_last_line,
struct line_content *mod_first_line,
struct line_content *restored_last_line,
struct line_content *restored_first_line)
{
print_boundaries("Before modification", self);
signal_state(self->mod_info, SETUP_MODIFY_MAPS);
wait_for_state(self->mod_info, SETUP_MAPS_MODIFIED);
/* Copy last line of the first page and first line of the last page */
if (!read_boundary_lines(self, mod_last_line, mod_first_line))
return false;
print_boundaries("After modification", self);
signal_state(self->mod_info, SETUP_RESTORE_MAPS);
wait_for_state(self->mod_info, SETUP_MAPS_RESTORED);
/* Copy last line of the first page and first line of the last page */
if (!read_boundary_lines(self, restored_last_line, restored_first_line))
return false;
print_boundaries("After restore", self);
if (!self->mod_info->vma_mod_check(mod_last_line, mod_first_line,
restored_last_line, restored_first_line))
return false;
/*
* The content of these lines after modify+resore should be the same
* as the original.
*/
return strcmp(restored_last_line->text, self->last_line.text) == 0 &&
strcmp(restored_first_line->text, self->first_line.text) == 0;
}
static inline bool split_vma(FIXTURE_DATA(proc_maps_race) *self)
{
return mmap(self->mod_info->addr, self->page_size, self->mod_info->prot | PROT_EXEC,
MAP_PRIVATE | MAP_ANONYMOUS | MAP_FIXED, -1, 0) != MAP_FAILED;
}
static inline bool merge_vma(FIXTURE_DATA(proc_maps_race) *self)
{
return mmap(self->mod_info->addr, self->page_size, self->mod_info->prot,
MAP_PRIVATE | MAP_ANONYMOUS | MAP_FIXED, -1, 0) != MAP_FAILED;
}
static inline bool check_split_result(struct line_content *mod_last_line,
struct line_content *mod_first_line,
struct line_content *restored_last_line,
struct line_content *restored_first_line)
{
/* Make sure vmas at the boundaries are changing */
return strcmp(mod_last_line->text, restored_last_line->text) != 0 &&
strcmp(mod_first_line->text, restored_first_line->text) != 0;
}
static inline bool shrink_vma(FIXTURE_DATA(proc_maps_race) *self)
{
return mremap(self->mod_info->addr, self->page_size * 3,
self->page_size, 0) != MAP_FAILED;
}
static inline bool expand_vma(FIXTURE_DATA(proc_maps_race) *self)
{
return mremap(self->mod_info->addr, self->page_size,
self->page_size * 3, 0) != MAP_FAILED;
}
static inline bool check_shrink_result(struct line_content *mod_last_line,
struct line_content *mod_first_line,
struct line_content *restored_last_line,
struct line_content *restored_first_line)
{
/* Make sure only the last vma of the first page is changing */
return strcmp(mod_last_line->text, restored_last_line->text) != 0 &&
strcmp(mod_first_line->text, restored_first_line->text) == 0;
}
static inline bool remap_vma(FIXTURE_DATA(proc_maps_race) *self)
{
/*
* Remap the last page of the next vma into the middle of the vma.
* This splits the current vma and the first and middle parts (the
* parts at lower addresses) become the last vma objserved in the
* first page and the first vma observed in the last page.
*/
return mremap(self->mod_info->next_addr + self->page_size * 2, self->page_size,
self->page_size, MREMAP_FIXED | MREMAP_MAYMOVE | MREMAP_DONTUNMAP,
self->mod_info->addr + self->page_size) != MAP_FAILED;
}
static inline bool patch_vma(FIXTURE_DATA(proc_maps_race) *self)
{
return mprotect(self->mod_info->addr + self->page_size, self->page_size,
self->mod_info->prot) == 0;
}
static inline bool check_remap_result(struct line_content *mod_last_line,
struct line_content *mod_first_line,
struct line_content *restored_last_line,
struct line_content *restored_first_line)
{
/* Make sure vmas at the boundaries are changing */
return strcmp(mod_last_line->text, restored_last_line->text) != 0 &&
strcmp(mod_first_line->text, restored_first_line->text) != 0;
}
FIXTURE_SETUP(proc_maps_race)
{
const char *verbose = getenv("VERBOSE");
const char *duration = getenv("DURATION");
struct vma_modifier_info *mod_info;
pthread_mutexattr_t mutex_attr;
pthread_condattr_t cond_attr;
unsigned long duration_sec;
char fname[32];
self->page_size = (unsigned long)sysconf(_SC_PAGESIZE);
self->verbose = verbose && !strncmp(verbose, "1", 1);
duration_sec = duration ? atol(duration) : 0;
self->duration_sec = duration_sec ? duration_sec : 5UL;
/*
* Have to map enough vmas for /proc/pid/maps to contain more than one
* page worth of vmas. Assume at least 32 bytes per line in maps output
*/
self->vma_count = self->page_size / 32 + 1;
self->shared_mem_size = sizeof(struct vma_modifier_info) + self->vma_count * sizeof(void *);
/* map shared memory for communication with the child process */
self->mod_info = (struct vma_modifier_info *)mmap(NULL, self->shared_mem_size,
PROT_READ | PROT_WRITE, MAP_SHARED | MAP_ANONYMOUS, -1, 0);
ASSERT_NE(self->mod_info, MAP_FAILED);
mod_info = self->mod_info;
/* Initialize shared members */
pthread_mutexattr_init(&mutex_attr);
pthread_mutexattr_setpshared(&mutex_attr, PTHREAD_PROCESS_SHARED);
ASSERT_EQ(pthread_mutex_init(&mod_info->sync_lock, &mutex_attr), 0);
pthread_condattr_init(&cond_attr);
pthread_condattr_setpshared(&cond_attr, PTHREAD_PROCESS_SHARED);
ASSERT_EQ(pthread_cond_init(&mod_info->sync_cond, &cond_attr), 0);
mod_info->vma_count = self->vma_count;
mod_info->curr_state = INIT;
mod_info->exit = false;
self->pid = fork();
if (!self->pid) {
/* Child process modifying the address space */
int prot = PROT_READ | PROT_WRITE;
int i;
for (i = 0; i < mod_info->vma_count; i++) {
mod_info->child_mapped_addr[i] = mmap(NULL, self->page_size * 3, prot,
MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
ASSERT_NE(mod_info->child_mapped_addr[i], MAP_FAILED);
/* change protection in adjacent maps to prevent merging */
prot ^= PROT_WRITE;
}
signal_state(mod_info, CHILD_READY);
wait_for_state(mod_info, PARENT_READY);
while (true) {
signal_state(mod_info, SETUP_READY);
wait_for_state(mod_info, SETUP_MODIFY_MAPS);
if (mod_info->exit)
break;
ASSERT_TRUE(mod_info->vma_modify(self));
signal_state(mod_info, SETUP_MAPS_MODIFIED);
wait_for_state(mod_info, SETUP_RESTORE_MAPS);
ASSERT_TRUE(mod_info->vma_restore(self));
signal_state(mod_info, SETUP_MAPS_RESTORED);
wait_for_state(mod_info, TEST_READY);
while (mod_info->curr_state != TEST_DONE) {
ASSERT_TRUE(mod_info->vma_modify(self));
ASSERT_TRUE(mod_info->vma_restore(self));
}
}
for (i = 0; i < mod_info->vma_count; i++)
munmap(mod_info->child_mapped_addr[i], self->page_size * 3);
exit(0);
}
sprintf(fname, "/proc/%d/maps", self->pid);
self->maps_fd = open(fname, O_RDONLY);
ASSERT_NE(self->maps_fd, -1);
/* Wait for the child to map the VMAs */
wait_for_state(mod_info, CHILD_READY);
/* Read first two pages */
self->page1.data = malloc(self->page_size);
ASSERT_NE(self->page1.data, NULL);
self->page2.data = malloc(self->page_size);
ASSERT_NE(self->page2.data, NULL);
ASSERT_TRUE(read_boundary_lines(self, &self->last_line, &self->first_line));
/*
* Find the addresses corresponding to the last line in the first page
* and the first line in the last page.
*/
mod_info->addr = NULL;
mod_info->next_addr = NULL;
for (int i = 0; i < mod_info->vma_count; i++) {
if (mod_info->child_mapped_addr[i] == (void *)self->last_line.start_addr) {
mod_info->addr = mod_info->child_mapped_addr[i];
mod_info->prot = PROT_READ;
/* Even VMAs have write permission */
if ((i % 2) == 0)
mod_info->prot |= PROT_WRITE;
} else if (mod_info->child_mapped_addr[i] == (void *)self->first_line.start_addr) {
mod_info->next_addr = mod_info->child_mapped_addr[i];
}
if (mod_info->addr && mod_info->next_addr)
break;
}
ASSERT_TRUE(mod_info->addr && mod_info->next_addr);
signal_state(mod_info, PARENT_READY);
}
FIXTURE_TEARDOWN(proc_maps_race)
{
int status;
stop_vma_modifier(self->mod_info);
free(self->page2.data);
free(self->page1.data);
for (int i = 0; i < self->vma_count; i++)
munmap(self->mod_info->child_mapped_addr[i], self->page_size);
close(self->maps_fd);
waitpid(self->pid, &status, 0);
munmap(self->mod_info, self->shared_mem_size);
}
TEST_F(proc_maps_race, test_maps_tearing_from_split)
{
struct vma_modifier_info *mod_info = self->mod_info;
struct line_content split_last_line;
struct line_content split_first_line;
struct line_content restored_last_line;
struct line_content restored_first_line;
wait_for_state(mod_info, SETUP_READY);
/* re-read the file to avoid using stale data from previous test */
ASSERT_TRUE(read_boundary_lines(self, &self->last_line, &self->first_line));
mod_info->vma_modify = split_vma;
mod_info->vma_restore = merge_vma;
mod_info->vma_mod_check = check_split_result;
report_test_start("Tearing from split", self->verbose);
ASSERT_TRUE(capture_mod_pattern(self, &split_last_line, &split_first_line,
&restored_last_line, &restored_first_line));
/* Now start concurrent modifications for self->duration_sec */
signal_state(mod_info, TEST_READY);
struct line_content new_last_line;
struct line_content new_first_line;
struct timespec start_ts, end_ts;
clock_gettime(CLOCK_MONOTONIC_COARSE, &start_ts);
start_test_loop(&start_ts, self->verbose);
do {
bool last_line_changed;
bool first_line_changed;
ASSERT_TRUE(read_boundary_lines(self, &new_last_line, &new_first_line));
/* Check if we read vmas after split */
if (!strcmp(new_last_line.text, split_last_line.text)) {
/*
* The vmas should be consistent with split results,
* however if vma was concurrently restored after a
* split, it can be reported twice (first the original
* split one, then the same vma but extended after the
* merge) because we found it as the next vma again.
* In that case new first line will be the same as the
* last restored line.
*/
ASSERT_FALSE(print_boundaries_on(
strcmp(new_first_line.text, split_first_line.text) &&
strcmp(new_first_line.text, restored_last_line.text),
"Split result invalid", self));
} else {
/* The vmas should be consistent with merge results */
ASSERT_FALSE(print_boundaries_on(
strcmp(new_last_line.text, restored_last_line.text),
"Merge result invalid", self));
ASSERT_FALSE(print_boundaries_on(
strcmp(new_first_line.text, restored_first_line.text),
"Merge result invalid", self));
}
/*
* First and last lines should change in unison. If the last
* line changed then the first line should change as well and
* vice versa.
*/
last_line_changed = strcmp(new_last_line.text, self->last_line.text) != 0;
first_line_changed = strcmp(new_first_line.text, self->first_line.text) != 0;
ASSERT_EQ(last_line_changed, first_line_changed);
clock_gettime(CLOCK_MONOTONIC_COARSE, &end_ts);
end_test_iteration(&end_ts, self->verbose);
} while (end_ts.tv_sec - start_ts.tv_sec < self->duration_sec);
end_test_loop(self->verbose);
/* Signal the modifyer thread to stop and wait until it exits */
signal_state(mod_info, TEST_DONE);
}
TEST_F(proc_maps_race, test_maps_tearing_from_resize)
{
struct vma_modifier_info *mod_info = self->mod_info;
struct line_content shrunk_last_line;
struct line_content shrunk_first_line;
struct line_content restored_last_line;
struct line_content restored_first_line;
wait_for_state(mod_info, SETUP_READY);
/* re-read the file to avoid using stale data from previous test */
ASSERT_TRUE(read_boundary_lines(self, &self->last_line, &self->first_line));
mod_info->vma_modify = shrink_vma;
mod_info->vma_restore = expand_vma;
mod_info->vma_mod_check = check_shrink_result;
report_test_start("Tearing from resize", self->verbose);
ASSERT_TRUE(capture_mod_pattern(self, &shrunk_last_line, &shrunk_first_line,
&restored_last_line, &restored_first_line));
/* Now start concurrent modifications for self->duration_sec */
signal_state(mod_info, TEST_READY);
struct line_content new_last_line;
struct line_content new_first_line;
struct timespec start_ts, end_ts;
clock_gettime(CLOCK_MONOTONIC_COARSE, &start_ts);
start_test_loop(&start_ts, self->verbose);
do {
ASSERT_TRUE(read_boundary_lines(self, &new_last_line, &new_first_line));
/* Check if we read vmas after shrinking it */
if (!strcmp(new_last_line.text, shrunk_last_line.text)) {
/*
* The vmas should be consistent with shrunk results,
* however if the vma was concurrently restored, it
* can be reported twice (first as shrunk one, then
* as restored one) because we found it as the next vma
* again. In that case new first line will be the same
* as the last restored line.
*/
ASSERT_FALSE(print_boundaries_on(
strcmp(new_first_line.text, shrunk_first_line.text) &&
strcmp(new_first_line.text, restored_last_line.text),
"Shrink result invalid", self));
} else {
/* The vmas should be consistent with the original/resored state */
ASSERT_FALSE(print_boundaries_on(
strcmp(new_last_line.text, restored_last_line.text),
"Expand result invalid", self));
ASSERT_FALSE(print_boundaries_on(
strcmp(new_first_line.text, restored_first_line.text),
"Expand result invalid", self));
}
clock_gettime(CLOCK_MONOTONIC_COARSE, &end_ts);
end_test_iteration(&end_ts, self->verbose);
} while (end_ts.tv_sec - start_ts.tv_sec < self->duration_sec);
end_test_loop(self->verbose);
/* Signal the modifyer thread to stop and wait until it exits */
signal_state(mod_info, TEST_DONE);
}
TEST_F(proc_maps_race, test_maps_tearing_from_remap)
{
struct vma_modifier_info *mod_info = self->mod_info;
struct line_content remapped_last_line;
struct line_content remapped_first_line;
struct line_content restored_last_line;
struct line_content restored_first_line;
wait_for_state(mod_info, SETUP_READY);
/* re-read the file to avoid using stale data from previous test */
ASSERT_TRUE(read_boundary_lines(self, &self->last_line, &self->first_line));
mod_info->vma_modify = remap_vma;
mod_info->vma_restore = patch_vma;
mod_info->vma_mod_check = check_remap_result;
report_test_start("Tearing from remap", self->verbose);
ASSERT_TRUE(capture_mod_pattern(self, &remapped_last_line, &remapped_first_line,
&restored_last_line, &restored_first_line));
/* Now start concurrent modifications for self->duration_sec */
signal_state(mod_info, TEST_READY);
struct line_content new_last_line;
struct line_content new_first_line;
struct timespec start_ts, end_ts;
clock_gettime(CLOCK_MONOTONIC_COARSE, &start_ts);
start_test_loop(&start_ts, self->verbose);
do {
ASSERT_TRUE(read_boundary_lines(self, &new_last_line, &new_first_line));
/* Check if we read vmas after remapping it */
if (!strcmp(new_last_line.text, remapped_last_line.text)) {
/*
* The vmas should be consistent with remap results,
* however if the vma was concurrently restored, it
* can be reported twice (first as split one, then
* as restored one) because we found it as the next vma
* again. In that case new first line will be the same
* as the last restored line.
*/
ASSERT_FALSE(print_boundaries_on(
strcmp(new_first_line.text, remapped_first_line.text) &&
strcmp(new_first_line.text, restored_last_line.text),
"Remap result invalid", self));
} else {
/* The vmas should be consistent with the original/resored state */
ASSERT_FALSE(print_boundaries_on(
strcmp(new_last_line.text, restored_last_line.text),
"Remap restore result invalid", self));
ASSERT_FALSE(print_boundaries_on(
strcmp(new_first_line.text, restored_first_line.text),
"Remap restore result invalid", self));
}
clock_gettime(CLOCK_MONOTONIC_COARSE, &end_ts);
end_test_iteration(&end_ts, self->verbose);
} while (end_ts.tv_sec - start_ts.tv_sec < self->duration_sec);
end_test_loop(self->verbose);
/* Signal the modifyer thread to stop and wait until it exits */
signal_state(mod_info, TEST_DONE);
}
TEST_HARNESS_MAIN
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