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proc: test how it holds up with mapping'less process

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Create process without mappings and check

	/proc/*/maps
	/proc/*/numa_maps
	/proc/*/smaps
	/proc/*/smaps_rollup

They must be empty (excluding vsyscall page) or full of zeroes.

Retroactively this test should've caught embarassing /proc/*/smaps_rollup
oops:

[17752.703567] BUG: kernel NULL pointer dereference, address: 0000000000000000
[17752.703580] #PF: supervisor read access in kernel mode
[17752.703583] #PF: error_code(0x0000) - not-present page
[17752.703587] PGD 0 P4D 0
[17752.703593] Oops: 0000 [#1] PREEMPT SMP PTI
[17752.703598] CPU: 0 PID: 60649 Comm: cat Tainted: G        W         5.19.9-100.fc35.x86_64 #1
[17752.703603] Hardware name: To Be Filled By O.E.M. To Be Filled By O.E.M./X99 Extreme6/3.1, BIOS P3.30 08/05/2016
[17752.703607] RIP: 0010:show_smaps_rollup+0x159/0x2e0

Note 1:
	ProtectionKey field in /proc/*/smaps is optional,
	so check most of its contents, not everything.

Note 2:
	due to the nature of this test, child process hardly can signal
	its readiness (after unmapping everything!) to parent.
	I feel like "sleep(1)" is justified.
	If you know how to do it without sleep please tell me.

Note 3:
	/proc/*/statm is not tested but can be.

Link: https://lkml.kernel.org/r/Yz3liL6Dn+n2SD8Q@localhost.localdomain
Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
Alexey Dobriyan 2022-10-05 23:14:00 +03:00 committed by Andrew Morton
parent 0f4107d179
commit 5bc73bb345
3 changed files with 388 additions and 0 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

1
tools/testing/selftests/proc/.gitignore vendored
View File

@ -5,6 +5,7 @@
/proc-fsconfig-hidepid
/proc-loadavg-001
/proc-multiple-procfs
/proc-empty-vm
/proc-pid-vm
/proc-self-map-files-001
/proc-self-map-files-002

1
tools/testing/selftests/proc/Makefile
View File

@ -8,6 +8,7 @@ TEST_GEN_PROGS += fd-001-lookup
TEST_GEN_PROGS += fd-002-posix-eq
TEST_GEN_PROGS += fd-003-kthread
TEST_GEN_PROGS += proc-loadavg-001
TEST_GEN_PROGS += proc-empty-vm
TEST_GEN_PROGS += proc-pid-vm
TEST_GEN_PROGS += proc-self-map-files-001
TEST_GEN_PROGS += proc-self-map-files-002

386
tools/testing/selftests/proc/proc-empty-vm.c Normal file
View File

@ -0,0 +1,386 @@
/*
* Copyright (c) 2022 Alexey Dobriyan <adobriyan@gmail.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.
*/
/*
* Create a process without mappings by unmapping everything at once and
* holding it with ptrace(2). See what happens to
*
* /proc/${pid}/maps
* /proc/${pid}/numa_maps
* /proc/${pid}/smaps
* /proc/${pid}/smaps_rollup
*/
#undef NDEBUG
#include <assert.h>
#include <errno.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <fcntl.h>
#include <sys/mman.h>
#include <sys/ptrace.h>
#include <sys/resource.h>
#include <sys/types.h>
#include <sys/wait.h>
#include <unistd.h>
/*
* 0: vsyscall VMA doesn't exist vsyscall=none
* 1: vsyscall VMA is --xp vsyscall=xonly
* 2: vsyscall VMA is r-xp vsyscall=emulate
*/
static int g_vsyscall;
static const char *g_proc_pid_maps_vsyscall;
static const char *g_proc_pid_smaps_vsyscall;
static const char proc_pid_maps_vsyscall_0[] = "";
static const char proc_pid_maps_vsyscall_1[] =
"ffffffffff600000-ffffffffff601000 --xp 00000000 00:00 0 [vsyscall]\n";
static const char proc_pid_maps_vsyscall_2[] =
"ffffffffff600000-ffffffffff601000 r-xp 00000000 00:00 0 [vsyscall]\n";
static const char proc_pid_smaps_vsyscall_0[] = "";
static const char proc_pid_smaps_vsyscall_1[] =
"ffffffffff600000-ffffffffff601000 r-xp 00000000 00:00 0 [vsyscall]\n"
"Size: 4 kB\n"
"KernelPageSize: 4 kB\n"
"MMUPageSize: 4 kB\n"
"Rss: 0 kB\n"
"Pss: 0 kB\n"
"Pss_Dirty: 0 kB\n"
"Shared_Clean: 0 kB\n"
"Shared_Dirty: 0 kB\n"
"Private_Clean: 0 kB\n"
"Private_Dirty: 0 kB\n"
"Referenced: 0 kB\n"
"Anonymous: 0 kB\n"
"LazyFree: 0 kB\n"
"AnonHugePages: 0 kB\n"
"ShmemPmdMapped: 0 kB\n"
"FilePmdMapped: 0 kB\n"
"Shared_Hugetlb: 0 kB\n"
"Private_Hugetlb: 0 kB\n"
"Swap: 0 kB\n"
"SwapPss: 0 kB\n"
"Locked: 0 kB\n"
"THPeligible: 0\n"
/*
* "ProtectionKey:" field is conditional. It is possible to check it as well,
* but I don't have such machine.
*/
;
static const char proc_pid_smaps_vsyscall_2[] =
"ffffffffff600000-ffffffffff601000 --xp 00000000 00:00 0 [vsyscall]\n"
"Size: 4 kB\n"
"KernelPageSize: 4 kB\n"
"MMUPageSize: 4 kB\n"
"Rss: 0 kB\n"
"Pss: 0 kB\n"
"Pss_Dirty: 0 kB\n"
"Shared_Clean: 0 kB\n"
"Shared_Dirty: 0 kB\n"
"Private_Clean: 0 kB\n"
"Private_Dirty: 0 kB\n"
"Referenced: 0 kB\n"
"Anonymous: 0 kB\n"
"LazyFree: 0 kB\n"
"AnonHugePages: 0 kB\n"
"ShmemPmdMapped: 0 kB\n"
"FilePmdMapped: 0 kB\n"
"Shared_Hugetlb: 0 kB\n"
"Private_Hugetlb: 0 kB\n"
"Swap: 0 kB\n"
"SwapPss: 0 kB\n"
"Locked: 0 kB\n"
"THPeligible: 0\n"
/*
* "ProtectionKey:" field is conditional. It is possible to check it as well,
* but I'm too tired.
*/
;
static void sigaction_SIGSEGV(int _, siginfo_t *__, void *___)
{
_exit(EXIT_FAILURE);
}
static void sigaction_SIGSEGV_vsyscall(int _, siginfo_t *__, void *___)
{
_exit(g_vsyscall);
}
/*
* vsyscall page can't be unmapped, probe it directly.
*/
static void vsyscall(void)
{
pid_t pid;
int wstatus;
pid = fork();
if (pid < 0) {
fprintf(stderr, "fork, errno %d\n", errno);
exit(1);
}
if (pid == 0) {
setrlimit(RLIMIT_CORE, &(struct rlimit){});
/* Hide "segfault at ffffffffff600000" messages. */
struct sigaction act = {};
act.sa_flags = SA_SIGINFO;
act.sa_sigaction = sigaction_SIGSEGV_vsyscall;
sigaction(SIGSEGV, &act, NULL);
g_vsyscall = 0;
/* gettimeofday(NULL, NULL); */
asm volatile (
"call %P0"
:
: "i" (0xffffffffff600000), "D" (NULL), "S" (NULL)
: "rax", "rcx", "r11"
);
g_vsyscall = 1;
*(volatile int *)0xffffffffff600000UL;
g_vsyscall = 2;
exit(g_vsyscall);
}
waitpid(pid, &wstatus, 0);
if (WIFEXITED(wstatus)) {
g_vsyscall = WEXITSTATUS(wstatus);
} else {
fprintf(stderr, "error: vsyscall wstatus %08x\n", wstatus);
exit(1);
}
}
static int test_proc_pid_maps(pid_t pid)
{
char buf[4096];
snprintf(buf, sizeof(buf), "/proc/%u/maps", pid);
int fd = open(buf, O_RDONLY);
if (fd == -1) {
perror("open /proc/${pid}/maps");
return EXIT_FAILURE;
} else {
ssize_t rv = read(fd, buf, sizeof(buf));
close(fd);
if (g_vsyscall == 0) {
assert(rv == 0);
} else {
size_t len = strlen(g_proc_pid_maps_vsyscall);
assert(rv == len);
assert(memcmp(buf, g_proc_pid_maps_vsyscall, len) == 0);
}
return EXIT_SUCCESS;
}
}
static int test_proc_pid_numa_maps(pid_t pid)
{
char buf[4096];
snprintf(buf, sizeof(buf), "/proc/%u/numa_maps", pid);
int fd = open(buf, O_RDONLY);
if (fd == -1) {
if (errno == ENOENT) {
/*
* /proc/${pid}/numa_maps is under CONFIG_NUMA,
* it doesn't necessarily exist.
*/
return EXIT_SUCCESS;
}
perror("open /proc/${pid}/numa_maps");
return EXIT_FAILURE;
} else {
ssize_t rv = read(fd, buf, sizeof(buf));
close(fd);
assert(rv == 0);
return EXIT_SUCCESS;
}
}
static int test_proc_pid_smaps(pid_t pid)
{
char buf[4096];
snprintf(buf, sizeof(buf), "/proc/%u/smaps", pid);
int fd = open(buf, O_RDONLY);
if (fd == -1) {
if (errno == ENOENT) {
/*
* /proc/${pid}/smaps is under CONFIG_PROC_PAGE_MONITOR,
* it doesn't necessarily exist.
*/
return EXIT_SUCCESS;
}
perror("open /proc/${pid}/smaps");
return EXIT_FAILURE;
} else {
ssize_t rv = read(fd, buf, sizeof(buf));
close(fd);
if (g_vsyscall == 0) {
assert(rv == 0);
} else {
size_t len = strlen(g_proc_pid_maps_vsyscall);
/* TODO "ProtectionKey:" */
assert(rv > len);
assert(memcmp(buf, g_proc_pid_maps_vsyscall, len) == 0);
}
return EXIT_SUCCESS;
}
}
static const char g_smaps_rollup[] =
"00000000-00000000 ---p 00000000 00:00 0 [rollup]\n"
"Rss: 0 kB\n"
"Pss: 0 kB\n"
"Pss_Dirty: 0 kB\n"
"Pss_Anon: 0 kB\n"
"Pss_File: 0 kB\n"
"Pss_Shmem: 0 kB\n"
"Shared_Clean: 0 kB\n"
"Shared_Dirty: 0 kB\n"
"Private_Clean: 0 kB\n"
"Private_Dirty: 0 kB\n"
"Referenced: 0 kB\n"
"Anonymous: 0 kB\n"
"LazyFree: 0 kB\n"
"AnonHugePages: 0 kB\n"
"ShmemPmdMapped: 0 kB\n"
"FilePmdMapped: 0 kB\n"
"Shared_Hugetlb: 0 kB\n"
"Private_Hugetlb: 0 kB\n"
"Swap: 0 kB\n"
"SwapPss: 0 kB\n"
"Locked: 0 kB\n"
;
static int test_proc_pid_smaps_rollup(pid_t pid)
{
char buf[4096];
snprintf(buf, sizeof(buf), "/proc/%u/smaps_rollup", pid);
int fd = open(buf, O_RDONLY);
if (fd == -1) {
if (errno == ENOENT) {
/*
* /proc/${pid}/smaps_rollup is under CONFIG_PROC_PAGE_MONITOR,
* it doesn't necessarily exist.
*/
return EXIT_SUCCESS;
}
perror("open /proc/${pid}/smaps_rollup");
return EXIT_FAILURE;
} else {
ssize_t rv = read(fd, buf, sizeof(buf));
close(fd);
assert(rv == sizeof(g_smaps_rollup) - 1);
assert(memcmp(buf, g_smaps_rollup, sizeof(g_smaps_rollup) - 1) == 0);
return EXIT_SUCCESS;
}
}
int main(void)
{
int rv = EXIT_SUCCESS;
vsyscall();
switch (g_vsyscall) {
case 0:
g_proc_pid_maps_vsyscall = proc_pid_maps_vsyscall_0;
g_proc_pid_smaps_vsyscall = proc_pid_smaps_vsyscall_0;
break;
case 1:
g_proc_pid_maps_vsyscall = proc_pid_maps_vsyscall_1;
g_proc_pid_smaps_vsyscall = proc_pid_smaps_vsyscall_1;
break;
case 2:
g_proc_pid_maps_vsyscall = proc_pid_maps_vsyscall_2;
g_proc_pid_smaps_vsyscall = proc_pid_smaps_vsyscall_2;
break;
default:
abort();
}
pid_t pid = fork();
if (pid == -1) {
perror("fork");
return EXIT_FAILURE;
} else if (pid == 0) {
rv = ptrace(PTRACE_TRACEME, 0, NULL, NULL);
if (rv != 0) {
if (errno == EPERM) {
fprintf(stderr,
"Did you know? ptrace(PTRACE_TRACEME) doesn't work under strace.\n"
);
kill(getppid(), SIGTERM);
return EXIT_FAILURE;
}
perror("ptrace PTRACE_TRACEME");
return EXIT_FAILURE;
}
/*
* Hide "segfault at ..." messages. Signal handler won't run.
*/
struct sigaction act = {};
act.sa_flags = SA_SIGINFO;
act.sa_sigaction = sigaction_SIGSEGV;
sigaction(SIGSEGV, &act, NULL);
#ifdef __amd64__
munmap(NULL, ((size_t)1 << 47) - 4096);
#else
#error "implement 'unmap everything'"
#endif
return EXIT_FAILURE;
} else {
/*
* TODO find reliable way to signal parent that munmap(2) completed.
* Child can't do it directly because it effectively doesn't exist
* anymore. Looking at child's VM files isn't 100% reliable either:
* due to a bug they may not become empty or empty-like.
*/
sleep(1);
if (rv == EXIT_SUCCESS) {
rv = test_proc_pid_maps(pid);
}
if (rv == EXIT_SUCCESS) {
rv = test_proc_pid_numa_maps(pid);
}
if (rv == EXIT_SUCCESS) {
rv = test_proc_pid_smaps(pid);
}
if (rv == EXIT_SUCCESS) {
rv = test_proc_pid_smaps_rollup(pid);
}
/*
* TODO test /proc/${pid}/statm, task_statm()
* ->start_code, ->end_code aren't updated by munmap().
* Output can be "0 0 0 2 0 0 0\n" where "2" can be anything.
*/
/* Cut the rope. */
int wstatus;
waitpid(pid, &wstatus, 0);
assert(WIFSTOPPED(wstatus));
assert(WSTOPSIG(wstatus) == SIGSEGV);
}
return rv;
}