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Subjectdrivers/scsi: GPF in sg_read
Hi,

I've got the following error report while fuzzing the kernel with syzkaller.

On commit 2868b2513aa732a99ea4a0a6bf10dc93c1f3dac2 (4.11+).

A reproducer and .config are attached.

kasan: CONFIG_KASAN_INLINE enabled
kasan: GPF could be caused by NULL-ptr deref or user memory access
general protection fault: 0000 [#1] SMP KASAN
Modules linked in:
CPU: 0 PID: 5226 Comm: a.out Not tainted 4.11.0+ #331
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Bochs 01/01/2011
task: ffff88006b958000 task.stack: ffff880064328000
RIP: 0010:__free_pages+0x0/0x20 ./include/linux/list.h:92
RSP: 0018:ffff88006432f980 EFLAGS: 00010202
RAX: 0000000000000000 RBX: ffff880066c44358 RCX: 1ffff1000cd88843
RDX: dead4ead00000000 RSI: 0000000000000001 RDI: dead4ead00000000
RBP: ffff88006432f9d8 R08: 1ffff1000c865eca R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000004
R13: 0000000000000020 R14: ffff880066c44200 R15: dffffc0000000000
FS: 00007fc454ac67c0(0000) GS:ffff88006ca00000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000020002000 CR3: 000000006affa000 CR4: 00000000000006f0
Call Trace:
sg_finish_rem_req+0x2a6/0x320 drivers/scsi/sg.c:1839
sg_new_read+0x3c/0x430 drivers/scsi/sg.c:567
sg_read+0x866/0x1830 drivers/scsi/sg.c:455
__vfs_read+0x5c3/0x750 fs/read_write.c:450
vfs_read+0x11e/0x350 fs/read_write.c:473
SYSC_read fs/read_write.c:589
SyS_read+0xfb/0x230 fs/read_write.c:582
entry_SYSCALL_64_fastpath+0x1f/0xbe arch/x86/entry/entry_64.S:204
RIP: 0033:0x7fc4541d9b79
RSP: 002b:00007ffc570f28e8 EFLAGS: 00000297 ORIG_RAX: 0000000000000000
RAX: ffffffffffffffda RBX: 00007ffc570f2bc0 RCX: 00007fc4541d9b79
RDX: 0000000000000000 RSI: 0000000020002f36 RDI: 0000000000000003
RBP: 00000000004010d0 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000297 R12: 0000000000000000
R13: 00007ffc570f2bc0 R14: 0000000000000000 R15: 0000000000000000
Code: 60 fc ff ff e8 02 35 14 00 4c 8b 95 48 fc ff ff 4c 8b 9d 50 fc
ff ff 4c 8b 8d 58 fc ff ff 48 8b 8d 60 fc ff ff e9 73 f9 ff ff 90 <f0>
ff 4f 1c 75 16 55 85 f6 48 89 e5 74 07 e8 5d 2f ff ff 5d c3
RIP: __free_pages+0x0/0x20 RSP: ffff88006432f980
[unhandled content-type:application/octet-stream]// autogenerated by syzkaller (http://github.com/google/syzkaller)

#ifndef __NR_read
#define __NR_read 0
#endif
#ifndef __NR_mmap
#define __NR_mmap 9
#endif
#ifndef __NR_syz_open_dev
#define __NR_syz_open_dev 1000002
#endif
#ifndef __NR_write
#define __NR_write 1
#endif

#define _GNU_SOURCE

#include <sys/ioctl.h>
#include <sys/mman.h>
#include <sys/mount.h>
#include <sys/prctl.h>
#include <sys/resource.h>
#include <sys/socket.h>
#include <sys/stat.h>
#include <sys/syscall.h>
#include <sys/time.h>
#include <sys/types.h>
#include <sys/wait.h>

#include <arpa/inet.h>
#include <linux/capability.h>
#include <linux/if.h>
#include <linux/if_ether.h>
#include <linux/if_tun.h>
#include <linux/ip.h>
#include <linux/kvm.h>
#include <linux/sched.h>
#include <linux/tcp.h>
#include <net/if_arp.h>

#include <assert.h>
#include <dirent.h>
#include <errno.h>
#include <fcntl.h>
#include <grp.h>
#include <pthread.h>
#include <setjmp.h>
#include <signal.h>
#include <stdarg.h>
#include <stdbool.h>
#include <stddef.h>
#include <stdint.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>

const int kFailStatus = 67;
const int kErrorStatus = 68;
const int kRetryStatus = 69;

__attribute__((noreturn)) void doexit(int status)
{
volatile unsigned i;
syscall(__NR_exit_group, status);
for (i = 0;; i++) {
}
}

__attribute__((noreturn)) void fail(const char* msg, ...)
{
int e = errno;
fflush(stdout);
va_list args;
va_start(args, msg);
vfprintf(stderr, msg, args);
va_end(args);
fprintf(stderr, " (errno %d)\n", e);
doexit((e == ENOMEM || e == EAGAIN) ? kRetryStatus : kFailStatus);
}

__attribute__((noreturn)) void exitf(const char* msg, ...)
{
int e = errno;
fflush(stdout);
va_list args;
va_start(args, msg);
vfprintf(stderr, msg, args);
va_end(args);
fprintf(stderr, " (errno %d)\n", e);
doexit(kRetryStatus);
}

static int flag_debug;

void debug(const char* msg, ...)
{
if (!flag_debug)
return;
va_list args;
va_start(args, msg);
vfprintf(stdout, msg, args);
va_end(args);
fflush(stdout);
}

__thread int skip_segv;
__thread jmp_buf segv_env;

static void segv_handler(int sig, siginfo_t* info, void* uctx)
{
uintptr_t addr = (uintptr_t)info->si_addr;
const uintptr_t prog_start = 1 << 20;
const uintptr_t prog_end = 100 << 20;
if (__atomic_load_n(&skip_segv, __ATOMIC_RELAXED) &&
(addr < prog_start || addr > prog_end)) {
debug("SIGSEGV on %p, skipping\n", addr);
_longjmp(segv_env, 1);
}
debug("SIGSEGV on %p, exiting\n", addr);
doexit(sig);
for (;;) {
}
}

static void install_segv_handler()
{
struct sigaction sa;
memset(&sa, 0, sizeof(sa));
sa.sa_sigaction = segv_handler;
sa.sa_flags = SA_NODEFER | SA_SIGINFO;
sigaction(SIGSEGV, &sa, NULL);
sigaction(SIGBUS, &sa, NULL);
}

#define NONFAILING(...) \
{ \
__atomic_fetch_add(&skip_segv, 1, __ATOMIC_SEQ_CST); \
if (_setjmp(segv_env) == 0) { \
__VA_ARGS__; \
} \
__atomic_fetch_sub(&skip_segv, 1, __ATOMIC_SEQ_CST); \
}

#define BITMASK_LEN(type, bf_len) (type)((1ull << (bf_len)) - 1)

#define BITMASK_LEN_OFF(type, bf_off, bf_len) \
(type)(BITMASK_LEN(type, (bf_len)) << (bf_off))

#define STORE_BY_BITMASK(type, addr, val, bf_off, bf_len) \
if ((bf_off) == 0 && (bf_len) == 0) { \
*(type*)(addr) = (type)(val); \
} else { \
type new_val = *(type*)(addr); \
new_val &= ~BITMASK_LEN_OFF(type, (bf_off), (bf_len)); \
new_val |= ((type)(val)&BITMASK_LEN(type, (bf_len))) << (bf_off); \
*(type*)(addr) = new_val; \
}

struct csum_inet {
uint32_t acc;
};

void csum_inet_init(struct csum_inet* csum)
{
csum->acc = 0;
}

void csum_inet_update(struct csum_inet* csum, const uint8_t* data,
size_t length)
{
if (length == 0)
return;

size_t i;
for (i = 0; i < length - 1; i += 2)
csum->acc += *(uint16_t*)&data[i];

if (length & 1)
csum->acc += (uint16_t)data[length - 1];

while (csum->acc > 0xffff)
csum->acc = (csum->acc & 0xffff) + (csum->acc >> 16);
}

uint16_t csum_inet_digest(struct csum_inet* csum)
{
return ~csum->acc;
}

static uintptr_t syz_open_dev(uintptr_t a0, uintptr_t a1, uintptr_t 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;
NONFAILING(strncpy(buf, (char*)a0, sizeof(buf)));
buf[sizeof(buf) - 1] = 0;
while ((hash = strchr(buf, '#'))) {
*hash = '0' + (char)(a1 % 10);
a1 /= 10;
}
return open(buf, a2, 0);
}
}

static uintptr_t execute_syscall(int nr, uintptr_t a0, uintptr_t a1,
uintptr_t a2, uintptr_t a3,
uintptr_t a4, uintptr_t a5,
uintptr_t a6, uintptr_t a7,
uintptr_t a8)
{
switch (nr) {
default:
return syscall(nr, a0, a1, a2, a3, a4, a5);
case __NR_syz_open_dev:
return syz_open_dev(a0, a1, a2);
}
}

static void setup_main_process()
{
struct sigaction sa;
memset(&sa, 0, sizeof(sa));
sa.sa_handler = SIG_IGN;
syscall(SYS_rt_sigaction, 0x20, &sa, NULL, 8);
syscall(SYS_rt_sigaction, 0x21, &sa, NULL, 8);
install_segv_handler();

char tmpdir_template[] = "./syzkaller.XXXXXX";
char* tmpdir = mkdtemp(tmpdir_template);
if (!tmpdir)
fail("failed to mkdtemp");
if (chmod(tmpdir, 0777))
fail("failed to chmod");
if (chdir(tmpdir))
fail("failed to chdir");
}

static void loop();

static void sandbox_common()
{
prctl(PR_SET_PDEATHSIG, SIGKILL, 0, 0, 0);
setpgrp();
setsid();

struct rlimit rlim;
rlim.rlim_cur = rlim.rlim_max = 128 << 20;
setrlimit(RLIMIT_AS, &rlim);
rlim.rlim_cur = rlim.rlim_max = 1 << 20;
setrlimit(RLIMIT_FSIZE, &rlim);
rlim.rlim_cur = rlim.rlim_max = 1 << 20;
setrlimit(RLIMIT_STACK, &rlim);
rlim.rlim_cur = rlim.rlim_max = 0;
setrlimit(RLIMIT_CORE, &rlim);

unshare(CLONE_NEWNS);
unshare(CLONE_NEWIPC);
unshare(CLONE_IO);
}

static int do_sandbox_none(int executor_pid, bool enable_tun)
{
int pid = fork();
if (pid)
return pid;

sandbox_common();

loop();
doexit(1);
}

static void remove_dir(const char* dir)
{
DIR* dp;
struct dirent* ep;
int iter = 0;
retry:
dp = opendir(dir);
if (dp == NULL) {
if (errno == EMFILE) {
exitf("opendir(%s) failed due to NOFILE, exiting");
}
exitf("opendir(%s) failed", dir);
}
while ((ep = readdir(dp))) {
if (strcmp(ep->d_name, ".") == 0 || strcmp(ep->d_name, "..") == 0)
continue;
char filename[FILENAME_MAX];
snprintf(filename, sizeof(filename), "%s/%s", dir, ep->d_name);
struct stat st;
if (lstat(filename, &st))
exitf("lstat(%s) failed", filename);
if (S_ISDIR(st.st_mode)) {
remove_dir(filename);
continue;
}
int i;
for (i = 0;; i++) {
debug("unlink(%s)\n", filename);
if (unlink(filename) == 0)
break;
if (errno == EROFS) {
debug("ignoring EROFS\n");
break;
}
if (errno != EBUSY || i > 100)
exitf("unlink(%s) failed", filename);
debug("umount(%s)\n", filename);
if (umount2(filename, MNT_DETACH))
exitf("umount(%s) failed", filename);
}
}
closedir(dp);
int i;
for (i = 0;; i++) {
debug("rmdir(%s)\n", dir);
if (rmdir(dir) == 0)
break;
if (i < 100) {
if (errno == EROFS) {
debug("ignoring EROFS\n");
break;
}
if (errno == EBUSY) {
debug("umount(%s)\n", dir);
if (umount2(dir, MNT_DETACH))
exitf("umount(%s) failed", dir);
continue;
}
if (errno == ENOTEMPTY) {
if (iter < 100) {
iter++;
goto retry;
}
}
}
exitf("rmdir(%s) failed", dir);
}
}

static uint64_t current_time_ms()
{
struct timespec ts;

if (clock_gettime(CLOCK_MONOTONIC, &ts))
fail("clock_gettime failed");
return (uint64_t)ts.tv_sec * 1000 + (uint64_t)ts.tv_nsec / 1000000;
}

static void test();

void loop()
{
int iter;
for (iter = 0;; iter++) {
char cwdbuf[256];
sprintf(cwdbuf, "./%d", iter);
if (mkdir(cwdbuf, 0777))
fail("failed to mkdir");
int pid = fork();
if (pid < 0)
fail("clone failed");
if (pid == 0) {
prctl(PR_SET_PDEATHSIG, SIGKILL, 0, 0, 0);
setpgrp();
if (chdir(cwdbuf))
fail("failed to chdir");
test();
doexit(0);
}
int status = 0;
uint64_t start = current_time_ms();
for (;;) {
int res = waitpid(-1, &status, __WALL | WNOHANG);
if (res == pid)
break;
usleep(1000);
if (current_time_ms() - start > 5 * 1000) {
kill(-pid, SIGKILL);
kill(pid, SIGKILL);
while (waitpid(-1, &status, __WALL) != pid) {
}
break;
}
}
remove_dir(cwdbuf);
}
}

long r[15];
void test()
{
memset(r, -1, sizeof(r));
r[0] = execute_syscall(__NR_mmap, 0x20000000ul, 0x5000ul, 0x3ul,
0x32ul, 0xfffffffffffffffful, 0x0ul, 0, 0, 0);
NONFAILING(memcpy((void*)0x20000000,
"\x2f\x64\x65\x76\x2f\x73\x67\x23\x00", 9));
r[2] = execute_syscall(__NR_syz_open_dev, 0x20000000ul, 0x0ul, 0x2ul,
0, 0, 0, 0, 0, 0);
NONFAILING(*(uint64_t*)0x20001fdc = (uint64_t)0x0);
NONFAILING(*(uint64_t*)0x20001fe4 = (uint64_t)0x0);
NONFAILING(*(uint16_t*)0x20001fec = (uint16_t)0x3);
NONFAILING(*(uint16_t*)0x20001fee = (uint16_t)0x4);
NONFAILING(*(uint32_t*)0x20001ff0 = (uint32_t)0x9);
NONFAILING(*(uint64_t*)0x20001ff4 = (uint64_t)0x0);
NONFAILING(*(uint64_t*)0x20001ffc = (uint64_t)0x2710);
NONFAILING(*(uint16_t*)0x20002004 = (uint16_t)0x7);
NONFAILING(*(uint16_t*)0x20002006 = (uint16_t)0x7);
NONFAILING(*(uint32_t*)0x20002008 = (uint32_t)0x8);
r[13] = execute_syscall(__NR_write, r[2], 0x20001fdcul, 0x30ul, 0, 0,
0, 0, 0, 0);
r[14] = execute_syscall(__NR_read, r[2], 0x20002f36ul, 0x0ul, 0, 0, 0,
0, 0, 0);
}
int main()
{
setup_main_process();
int pid = do_sandbox_none(0, false);
int status = 0;
while (waitpid(pid, &status, __WALL) != pid) {
}
return 0;
}
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