drm: GPF in drm_getcap

[Dmitry Vyukov]

Hello,

The following program triggers GPF in drm_getcap:

// autogenerated by syzkaller (http://github.com/google/syzkaller)
#include <fcntl.h>
#include <stddef.h>
#include <stdint.h>
#include <sys/ioctl.h>
#include <sys/stat.h>
#include <sys/syscall.h>
#include <sys/types.h>
#include <unistd.h>

int main()
{
  int fd = open("/dev/dri/card0", O_RDONLY);
  uint64_t data[2] = {0x11, 0x80};
  ioctl(fd, 0xc010640cul /*DRM_IOCTL_GET_CAP*/, data);
  return 0;
}


general protection fault: 0000 [#1] SMP DEBUG_PAGEALLOC KASAN
Modules linked in:
CPU: 1 PID: 5745 Comm: syz-executor Not tainted 4.8.0-rc5-next-20160905+ #14
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Bochs 01/01/2011
task: ffff8800310dc540 task.stack: ffff88003cbc0000
RIP: 0010:[<ffffffff834ca87b>]  [<ffffffff834ca87b>]
drm_getcap+0x34b/0x4f0 drivers/gpu/drm/drm_ioctl.c:260
RSP: 0018:ffff88003cbc7c28  EFLAGS: 00010202
RAX: 0000000000000058 RBX: ffff88003cbc7cf8 RCX: ffffc90001db0000
RDX: 000000000000005d RSI: ffff88003cbc7cf8 RDI: 00000000000002c0
RBP: ffff88003cbc7c50 R08: ffffed0007978fa1 R09: ffffed0007978fa0
R10: ffff88003cbc7d07 R11: ffffed0007978fa1 R12: fffffffffffffff0
R13: dffffc0000000000 R14: ffff88003bcc6850 R15: fffffffffffffff2
FS:  00007fcbf4e03700(0000) GS:ffff88003ed00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00000000006dce00 CR3: 0000000066135000 CR4: 00000000000006e0
DR0: 000000000000001e DR1: 000000000000001e DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000600
Stack:
 ffff88003c26db00 ffff88003cbc7cf8 ffffffff875a3000 ffffffff88cf0ee0
 fffffffffffffff2 ffff88003cbc7dc0 ffffffff834cb57c 000000000000e200
 1ffff10000000001 ffffffff875a1ba0 ffffffff882ae930 0000000000000010
Call Trace:
 [<ffffffff834cb57c>] drm_ioctl+0x54c/0xaf0 drivers/gpu/drm/drm_ioctl.c:728
 [<     inline     >] vfs_ioctl fs/ioctl.c:43
 [<ffffffff818a331c>] do_vfs_ioctl+0x18c/0x1080 fs/ioctl.c:675
 [<     inline     >] SYSC_ioctl fs/ioctl.c:690
 [<ffffffff818a429f>] SyS_ioctl+0x8f/0xc0 fs/ioctl.c:681
 [<ffffffff86e1a8c0>] entry_SYSCALL_64_fastpath+0x23/0xc1
Code: 3c 28 00 0f 85 88 01 00 00 49 8b 44 24 10 49 39 c6 4c 8d 60 f0
74 82 e8 64 19 10 fe 49 8d bc 24 d0 02 00 00 48 89 f8 48 c1 e8 03 <42>
80 3c 28 00 0f 85 6f 01 00 00 4d 8b bc 24 d0 02 00 00 49 8d
RIP  [<ffffffff834ca87b>] drm_getcap+0x34b/0x4f0 drivers/gpu/drm/drm_ioctl.c:260
 RSP <ffff88003cbc7c28>
---[ end trace c6e1afa8cd73b880 ]---


On commit 4affa544adb8077403893e62b9e327fcf87de6f7 (Sep 8) of linux-next.