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Message-ID: <CACT4Y+YC_42FPc+uXZ3baUwRPKaDB_xd=DabYftnp81CNkyc2w@mail.gmail.com>
Date:   Sun, 28 Aug 2016 19:36:59 +0200
From:   Dmitry Vyukov <dvyukov@...gle.com>
To:     airlied@...ux.ie, dri-devel@...ts.freedesktop.org,
        LKML <linux-kernel@...r.kernel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>
Cc:     syzkaller <syzkaller@...glegroups.com>,
        Kostya Serebryany <kcc@...gle.com>,
        Alexander Potapenko <glider@...gle.com>
Subject: drm: WARNING in ioremap_wc

Hello,

The following program triggers WARNING in ioremap_wc:

------------[ cut here ]------------
LoadPin: kernel-module denied obj="/memfd: (deleted)" pid=12061
cmdline="/tmp/syz-executor"
WARNING: CPU: 1 PID: 12056 at arch/x86/mm/ioremap.c:121[<      none
  >] __ioremap_caller+0x348/0x6b0 arch/x86/mm/ioremap.c:120
LoadPin: kernel-module denied obj="/memfd: (deleted)" pid=12063
cmdline="/tmp/syz-executor"
ioremap on RAM at 0x0000000020068000 - 0x0000000020068fff
Kernel panic - not syncing: panic_on_warn set ...

CPU: 1 PID: 12056 Comm: syz-executor Not tainted 4.8.0-rc3+ #32
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Bochs 01/01/2011
 ffffffff884b8280 ffff8800295777f0 ffffffff82d1b239 ffffffff00bd6000
 fffffbfff1097050 ffffffff86e8eec0 ffff8800295778c8 ffffffff86e7ad00
 dffffc0000000000 0000000000000009 ffff8800295778b8 ffffffff816ab4e3
Call Trace:
 [<     inline     >] __dump_stack lib/dump_stack.c:15
 [<ffffffff82d1b239>] dump_stack+0x12e/0x185 lib/dump_stack.c:51
 [<ffffffff816ab4e3>] panic+0x1e4/0x3ef kernel/panic.c:153
 [<ffffffff813808f4>] __warn+0x1c4/0x1e0 kernel/panic.c:509
 [<ffffffff813809bc>] warn_slowpath_fmt+0xac/0xd0 kernel/panic.c:532
 [<ffffffff8129a1c8>] __ioremap_caller+0x348/0x6b0 arch/x86/mm/ioremap.c:120
 [<ffffffff8129a5b6>] ioremap_wc+0x26/0x30 arch/x86/mm/ioremap.c:290
 [<ffffffff833ff70e>] drm_addmap_core+0xf1e/0x16c0
drivers/gpu/drm/drm_bufs.c:213
 [<ffffffff8340327a>] drm_legacy_addmap_ioctl+0x1ca/0x340
drivers/gpu/drm/drm_bufs.c:403
 [<ffffffff83410a5c>] drm_ioctl+0x7bc/0xc60 drivers/gpu/drm/drm_ioctl.c:724
 [<     inline     >] vfs_ioctl fs/ioctl.c:43
 [<ffffffff8186f1fc>] do_vfs_ioctl+0x18c/0x1080 fs/ioctl.c:675
 [<     inline     >] SYSC_ioctl fs/ioctl.c:690
 [<ffffffff8187017f>] SyS_ioctl+0x8f/0xc0 fs/ioctl.c:681
 [<ffffffff810088ff>] do_syscall_64+0x1df/0x640 arch/x86/entry/common.c:288
 [<ffffffff86c25543>] entry_SYSCALL64_slow_path+0x25/0x25
arch/x86/entry/entry_64.S:248

On commit 61c04572de404e52a655a36752e696bbcb483cf5 (Aug 25).


// autogenerated by syzkaller (http://github.com/google/syzkaller)
#ifndef __NR_syz_open_pts
#define __NR_syz_open_pts 1000002
#endif
#ifndef __NR_mmap
#define __NR_mmap 9
#endif
#ifndef __NR_syz_open_dev
#define __NR_syz_open_dev 1000001
#endif
#ifndef __NR_ioctl
#define __NR_ioctl 16
#endif
#ifndef __NR_syz_fuse_mount
#define __NR_syz_fuse_mount 1000003
#endif
#ifndef __NR_syz_fuseblk_mount
#define __NR_syz_fuseblk_mount 1000004
#endif

#include <fcntl.h>
#include <pthread.h>
#include <setjmp.h>
#include <signal.h>
#include <stddef.h>
#include <stdint.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/ioctl.h>
#include <sys/stat.h>
#include <sys/syscall.h>
#include <sys/types.h>
#include <unistd.h>

__thread int skip_segv;
__thread jmp_buf segv_env;

static void segv_handler(int sig, siginfo_t* info, void* uctx)
{
  if (__atomic_load_n(&skip_segv, __ATOMIC_RELAXED))
    _longjmp(segv_env, 1);
  exit(sig);
}

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);               \
  }

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;
    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 syz_open_pts(uintptr_t a0, uintptr_t a1)
{
  int ptyno = 0;
  if (ioctl(a0, TIOCGPTN, &ptyno))
    return -1;
  char buf[128];
  sprintf(buf, "/dev/pts/%d", ptyno);
  return open(buf, a1, 0);
}

static uintptr_t syz_fuse_mount(uintptr_t a0, uintptr_t a1,
                                uintptr_t a2, uintptr_t a3,
                                uintptr_t a4, uintptr_t a5)
{
  uint64_t target = a0;
  uint64_t mode = a1;
  uint64_t uid = a2;
  uint64_t gid = a3;
  uint64_t maxread = a4;
  uint64_t flags = a5;

  int fd = open("/dev/fuse", O_RDWR);
  if (fd == -1)
    return fd;
  char buf[1024];
  sprintf(buf, "fd=%d,user_id=%ld,group_id=%ld,rootmode=0%o", fd,
          (long)uid, (long)gid, (unsigned)mode & ~3u);
  if (maxread != 0)
    sprintf(buf + strlen(buf), ",max_read=%ld", (long)maxread);
  if (mode & 1)
    strcat(buf, ",default_permissions");
  if (mode & 2)
    strcat(buf, ",allow_other");
  syscall(SYS_mount, "", target, "fuse", flags, buf);
  return fd;
}

static uintptr_t syz_fuseblk_mount(uintptr_t a0, uintptr_t a1,
                                   uintptr_t a2, uintptr_t a3,
                                   uintptr_t a4, uintptr_t a5,
                                   uintptr_t a6, uintptr_t a7)
{
  uint64_t target = a0;
  uint64_t blkdev = a1;
  uint64_t mode = a2;
  uint64_t uid = a3;
  uint64_t gid = a4;
  uint64_t maxread = a5;
  uint64_t blksize = a6;
  uint64_t flags = a7;

  int fd = open("/dev/fuse", O_RDWR);
  if (fd == -1)
    return fd;
  if (syscall(SYS_mknodat, AT_FDCWD, blkdev, S_IFBLK, makedev(7, 199)))
    return fd;
  char buf[256];
  sprintf(buf, "fd=%d,user_id=%ld,group_id=%ld,rootmode=0%o", fd,
          (long)uid, (long)gid, (unsigned)mode & ~3u);
  if (maxread != 0)
    sprintf(buf + strlen(buf), ",max_read=%ld", (long)maxread);
  if (blksize != 0)
    sprintf(buf + strlen(buf), ",blksize=%ld", (long)blksize);
  if (mode & 1)
    strcat(buf, ",default_permissions");
  if (mode & 2)
    strcat(buf, ",allow_other");
  syscall(SYS_mount, blkdev, target, "fuseblk", flags, buf);
  return fd;
}

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);
  case __NR_syz_open_pts:
    return syz_open_pts(a0, a1);
  case __NR_syz_fuse_mount:
    return syz_fuse_mount(a0, a1, a2, a3, a4, a5);
  case __NR_syz_fuseblk_mount:
    return syz_fuseblk_mount(a0, a1, a2, a3, a4, a5, a6, a7);
  }
}

long r[10];

int main()
{
  install_segv_handler();
  memset(r, -1, sizeof(r));
  r[0] = execute_syscall(__NR_mmap, 0x20000000ul, 0x85a000ul, 0x3ul,
                         0x32ul, 0xfffffffffffffffful, 0x0ul, 0, 0, 0);
  NONFAILING(memcpy(
      (void*)0x20000000,
      "\x2f\x64\x65\x76\x2f\x64\x72\x69\x2f\x63\x61\x72\x64\x23\x00",
      15));
  r[2] = execute_syscall(__NR_syz_open_dev, 0x20000000ul, 0x0ul,
                         0x400ul, 0, 0, 0, 0, 0, 0);
  NONFAILING(*(uint64_t*)0x20858fd8 = (uint64_t)0x20068000);
  NONFAILING(*(uint64_t*)0x20858fe0 = (uint64_t)0x1000);
  NONFAILING(*(uint32_t*)0x20858fe8 = (uint32_t)0x1);
  NONFAILING(*(uint32_t*)0x20858fec = (uint32_t)0x30);
  NONFAILING(*(uint64_t*)0x20858ff0 = (uint64_t)0x20284000);
  NONFAILING(*(uint32_t*)0x20858ff8 = (uint32_t)0x1);
  r[9] = execute_syscall(__NR_ioctl, r[2], 0xc0286415ul, 0x20858fd8ul,
                         0, 0, 0, 0, 0, 0);
  return 0;
}

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