drm_mode_create_dumb_ioctl: divide error

[Tommi Rantala]

Hello,

Triggered this while fuzzing v3.17-rc1-51-g372b1db with Trinity.

Tommi


[drm:drm_mode_legacy_fb_format] *ERROR* bad bpp, assuming x8r8g8b8 pixel format
divide error: 0000 [#1] SMP DEBUG_PAGEALLOC
CPU: 0 PID: 2854 Comm: trinity-c7 Not tainted 3.17.0-rc1+ #14
Hardware name: Bochs Bochs, BIOS Bochs 01/01/2011
task: ffff88003926cac0 ti: ffff8800356b4000 task.ti: ffff8800356b4000
RIP: 0010:[<ffffffff816688e3>]  [<ffffffff816688e3>]
drm_mode_create_dumb_ioctl+0x53/0xa0
RSP: 0018:ffff8800356b7dc0  EFLAGS: 00010246
RAX: 00000000ffffffff RBX: ffff88003545da68 RCX: 0000000000000000
RDX: 0000000000000000 RSI: ffff8800356b7e18 RDI: ffff88003d5c67b0
RBP: ffff8800356b7dc8 R08: 0000000000000000 R09: 00000000ffffffff
R10: 00000000ffffffff R11: ffffffff817f6d30 R12: 00000000000000b2
R13: fffffffffffffff2 R14: ffff88003d5c67b0 R15: ffff88003545da68
FS:  00007f06208fa700(0000) GS:ffff88003fa00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000001903108 CR3: 0000000036efa000 CR4: 00000000000006f0
Stack:
 ffff8800356b7e18 ffff8800356b7ec8 ffffffff8165ac60 ffff8800356b7df8
 ffff8800356b7e18 ffff8800356b7e18 ffffffff824e1440 0000000000d52000
 0000000000000020 00000000c02064b2 00000000fffffff2 ffffffffffffffff
Call Trace:
 [<ffffffff8165ac60>] drm_ioctl+0x3b0/0x640
 [<ffffffff814b81b8>] ? avc_has_perm+0x218/0x2f0
 [<ffffffff814b7fc0>] ? avc_has_perm+0x20/0x2f0
 [<ffffffff81170bb8>] ? sched_clock_cpu+0xa8/0xf0
 [<ffffffff812922a0>] do_vfs_ioctl+0x4d0/0x510
 [<ffffffff814ba745>] ? selinux_file_ioctl+0xf5/0x100
 [<ffffffff8129232e>] SyS_ioctl+0x4e/0x80
 [<ffffffff822b10e9>] system_call_fastpath+0x16/0x1b
Code: 55 41 b9 ff ff ff ff 41 83 c0 07 44 89 c8 41 c1 e8 03 48 89 e5
53 48 89 d3 31 d2 f7 f1 41 39 c0 77 46 41 0f af c8 31 d2 44 89 c8 <f7>
f1 41 39 c2 77 36 41 0f af ca b8 ea ff ff ff 81 c1 ff 0f 00
RIP  [<ffffffff816688e3>] drm_mode_create_dumb_ioctl+0x53/0xa0
 RSP <ffff8800356b7dc0>
---[ end trace 6919129b71d9bf98 ]---
[drm:drm_mode_legacy_fb_format] *ERROR* bad bpp, assuming x8r8g8b8 pixel format



(gdb) list *0xffffffff816688e3
0xffffffff816688e3 is in drm_mode_create_dumb_ioctl
(drivers/gpu/drm/drm_crtc.c:4703).
4698            /* overflow checks for 32bit size calculations */
4699            cpp = DIV_ROUND_UP(args->bpp, 8);
4700            if (cpp > 0xffffffffU / args->width)
4701                    return -EINVAL;
4702            stride = cpp * args->width;
4703            if (args->height > 0xffffffffU / stride)
4704                    return -EINVAL;
4705
4706            /* test for wrap-around */
4707            size = args->height * stride;
(gdb) disassemble drm_mode_create_dumb_ioctl
Dump of assembler code for function drm_mode_create_dumb_ioctl:
   0xffffffff81668890 <+0>:     mov    0x20(%rdi),%rax
   0xffffffff81668894 <+4>:     mov    0x160(%rax),%r11
   0xffffffff8166889b <+11>:    test   %r11,%r11
   0xffffffff8166889e <+14>:    je     0xffffffff8166890f
<drm_mode_create_dumb_ioctl+127>
   0xffffffff816688a0 <+16>:    mov    0x4(%rsi),%ecx
   0xffffffff816688a3 <+19>:    test   %ecx,%ecx
   0xffffffff816688a5 <+21>:    je     0xffffffff81668918
<drm_mode_create_dumb_ioctl+136>
   0xffffffff816688a7 <+23>:    mov    (%rsi),%r10d
   0xffffffff816688aa <+26>:    test   %r10d,%r10d
   0xffffffff816688ad <+29>:    je     0xffffffff81668918
<drm_mode_create_dumb_ioctl+136>
   0xffffffff816688af <+31>:    mov    0x8(%rsi),%r8d
   0xffffffff816688b3 <+35>:    test   %r8d,%r8d
   0xffffffff816688b6 <+38>:    je     0xffffffff81668918
<drm_mode_create_dumb_ioctl+136>
   0xffffffff816688b8 <+40>:    push   %rbp
   0xffffffff816688b9 <+41>:    mov    $0xffffffff,%r9d
   0xffffffff816688bf <+47>:    add    $0x7,%r8d
   0xffffffff816688c3 <+51>:    mov    %r9d,%eax
   0xffffffff816688c6 <+54>:    shr    $0x3,%r8d
   0xffffffff816688ca <+58>:    mov    %rsp,%rbp
   0xffffffff816688cd <+61>:    push   %rbx
   0xffffffff816688ce <+62>:    mov    %rdx,%rbx
   0xffffffff816688d1 <+65>:    xor    %edx,%edx
   0xffffffff816688d3 <+67>:    div    %ecx
   0xffffffff816688d5 <+69>:    cmp    %eax,%r8d
   0xffffffff816688d8 <+72>:    ja     0xffffffff81668920
<drm_mode_create_dumb_ioctl+144>
   0xffffffff816688da <+74>:    imul   %r8d,%ecx
   0xffffffff816688de <+78>:    xor    %edx,%edx
   0xffffffff816688e0 <+80>:    mov    %r9d,%eax
   0xffffffff816688e3 <+83>:    div    %ecx
   0xffffffff816688e5 <+85>:    cmp    %eax,%r10d
   0xffffffff816688e8 <+88>:    ja     0xffffffff81668920
<drm_mode_create_dumb_ioctl+144>
   0xffffffff816688ea <+90>:    imul   %r10d,%ecx
   0xffffffff816688ee <+94>:    mov    $0xffffffea,%eax
   0xffffffff816688f3 <+99>:    add    $0xfff,%ecx
   0xffffffff816688f9 <+105>:   and    $0xfffff000,%ecx
   0xffffffff816688ff <+111>:   je     0xffffffff81668928
<drm_mode_create_dumb_ioctl+152>
   0xffffffff81668901 <+113>:   mov    %rsi,%rdx
   0xffffffff81668904 <+116>:   mov    %rdi,%rsi
   0xffffffff81668907 <+119>:   mov    %rbx,%rdi
   0xffffffff8166890a <+122>:   callq  *%r11
   0xffffffff8166890d <+125>:   jmp    0xffffffff81668928
<drm_mode_create_dumb_ioctl+152>
   0xffffffff8166890f <+127>:   mov    $0xffffffda,%eax
   0xffffffff81668914 <+132>:   retq
   0xffffffff81668915 <+133>:   nopl   (%rax)
   0xffffffff81668918 <+136>:   mov    $0xffffffea,%eax
   0xffffffff8166891d <+141>:   retq
   0xffffffff8166891e <+142>:   xchg   %ax,%ax
   0xffffffff81668920 <+144>:   mov    $0xffffffea,%eax
   0xffffffff81668925 <+149>:   nopl   (%rax)
   0xffffffff81668928 <+152>:   pop    %rbx
   0xffffffff81668929 <+153>:   pop    %rbp
   0xffffffff8166892a <+154>:   retq
End of assembler dump.
(gdb)