Hi On Thu, Aug 21, 2014 at 8:18 PM, Tommi Rantala <tt.rantala@xxxxxxxxx> wrote: > 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; Hm, this doesn't make sense to me. args->bpp/width/height are guaranteed to be non-zero and 32bit. Therefore, DIV_ROUND_UP() cannot return 0 and "cpp" is thus non-zero. The overflow check makes sure "cpp * args->width" cannot overflow, both are non-zero so "stride" is non-zero and valid. I cannot make much sense out of the x86 assembly below, so help welcome. Thanks David > 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) -- To unsubscribe from this list: send the line "unsubscribe trinity" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
