linux-kernel - Re: [PATCH v2] drm/radeon: evergreen_hpd_init()/_fini(): fix HPD IRQ bitset

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Message-ID: <87vb4ewv9m.fsf@gmail.com>
Date:	Tue, 22 Mar 2016 13:29:41 +0100
From:	Nicolai Stange <nicstange@...il.com>
To:	Alex Deucher <alexdeucher@...il.com>
Cc:	Nicolai Stange <nicstange@...il.com>,
	David Airlie <airlied@...ux.ie>,
	Alex Deucher <alexander.deucher@....com>,
	Christian König 
	<christian.koenig@....com>, LKML <linux-kernel@...r.kernel.org>,
	Maling list - DRI developers 
	<dri-devel@...ts.freedesktop.org>
Subject: Re: [PATCH v2] drm/radeon: evergreen_hpd_init()/_fini(): fix HPD IRQ bitset

Alex Deucher <alexdeucher@...il.com> writes:

> On Mon, Mar 21, 2016 at 8:10 AM, Nicolai Stange <nicstange@...il.com> wrote:
>> The values of all but the RADEON_HPD_NONE members of the radeon_hpd_id
>> enum transform 1:1 into bit positions within the 'enabled' bitset as
>> assembled by evergreen_hpd_init():
>>
>>   enabled |= 1 << radeon_connector->hpd.hpd;
>>
>> However, if ->hpd.hpd happens to equal RADEON_HPD_NONE == 0xff, UBSAN
>> reports
>>
>>   UBSAN: Undefined behaviour in drivers/gpu/drm/radeon/evergreen.c:1867:16
>>   shift exponent 255 is too large for 32-bit type 'int'
>>   [...]
>>   Call Trace:
>>    [<ffffffff818c4d35>] dump_stack+0xbc/0x117
>>    [<ffffffff818c4c79>] ? _atomic_dec_and_lock+0x169/0x169
>>    [<ffffffff819411bb>] ubsan_epilogue+0xd/0x4e
>>    [<ffffffff81941cbc>] __ubsan_handle_shift_out_of_bounds+0x1fb/0x254
>>    [<ffffffffa0ba7f2e>] ? atom_execute_table+0x3e/0x50 [radeon]
>>    [<ffffffff81941ac1>] ? __ubsan_handle_load_invalid_value+0x158/0x158
>>    [<ffffffffa0b87700>] ? radeon_get_pll_use_mask+0x130/0x130 [radeon]
>>    [<ffffffff81219930>] ? wake_up_klogd_work_func+0x60/0x60
>>    [<ffffffff8121a35e>] ? vprintk_default+0x3e/0x60
>>    [<ffffffffa0c603c4>] evergreen_hpd_init+0x274/0x2d0 [radeon]
>>    [<ffffffffa0c603c4>] ? evergreen_hpd_init+0x274/0x2d0 [radeon]
>>    [<ffffffffa0bd196e>] radeon_modeset_init+0x8ce/0x18d0 [radeon]
>>    [<ffffffffa0b71d86>] radeon_driver_load_kms+0x186/0x350 [radeon]
>>    [<ffffffffa03b6b16>] drm_dev_register+0xc6/0x100 [drm]
>>    [<ffffffffa03bc8c4>] drm_get_pci_dev+0xe4/0x490 [drm]
>>    [<ffffffff814b83f0>] ? kfree+0x220/0x370
>>    [<ffffffffa0b687c2>] radeon_pci_probe+0x112/0x140 [radeon]
>>    [...]
>>   =====================================================================
>>   radeon 0000:01:00.0: No connectors reported connected with modes
>>
>> At least on x86, there should be no user-visible impact as there
>>
>>   1 << 0xff == 1 << (0xff & 31) == 1 << 31
>>
>> holds and 31 > RADEON_MAX_HPD_PINS. Thus, this patch is a cosmetic one.
>>
>> All of the above applies analogously to evergreen_hpd_fini().
>>
>> Silence UBSAN by checking ->hpd.hpd for RADEON_HPD_NONE before oring it
>> into the 'enabled' bitset in evergreen_hpd_init() or the 'disabled' bitset
>> in evergreen_hpd_fini() respectively.
>>
>> Signed-off-by: Nicolai Stange <nicstange@...il.com>
>
> Can you please fix all instances of this?  This same pattern is
> repeated in various asic families.

Sure.

The places to fix are:
$ git grep -n '1 *<<.*hpd' -- drivers/gpu/drm/radeon/
drivers/gpu/drm/radeon/evergreen.c:1868:                        enabled |= 1 << radeon_connector->hpd.hpd;
drivers/gpu/drm/radeon/evergreen.c:1912:                        disabled |= 1 << radeon_connector->hpd.hpd;
drivers/gpu/drm/radeon/r100.c:595:              enable |= 1 << radeon_connector->hpd.hpd;
drivers/gpu/drm/radeon/r100.c:617:              disable |= 1 << radeon_connector->hpd.hpd;
drivers/gpu/drm/radeon/r600.c:1005:             enable |= 1 << radeon_connector->hpd.hpd;
drivers/gpu/drm/radeon/r600.c:1058:             disable |= 1 << radeon_connector->hpd.hpd;
drivers/gpu/drm/radeon/rs600.c:416:             enable |= 1 << radeon_connector->hpd.hpd;
drivers/gpu/drm/radeon/rs600.c:442:             disable |= 1 << radeon_connector->hpd.hpd;

May I throw all of those into one single patch?

Thanks,

Nicolai

>
>> ---
>>  Applicable to linux-next-20160321.
>>
>>  Changes to v1:
>>  - Turn commit message's impact part into a non-impact part.
>>
>>  drivers/gpu/drm/radeon/evergreen.c | 6 ++++--
>>  1 file changed, 4 insertions(+), 2 deletions(-)
>>
>> diff --git a/drivers/gpu/drm/radeon/evergreen.c b/drivers/gpu/drm/radeon/evergreen.c
>> index 76c4bdf..6360717 100644
>> --- a/drivers/gpu/drm/radeon/evergreen.c
>> +++ b/drivers/gpu/drm/radeon/evergreen.c
>> @@ -1864,7 +1864,8 @@ void evergreen_hpd_init(struct radeon_device *rdev)
>>                         break;
>>                 }
>>                 radeon_hpd_set_polarity(rdev, radeon_connector->hpd.hpd);
>> -               enabled |= 1 << radeon_connector->hpd.hpd;
>> +               if (radeon_connector->hpd.hpd != RADEON_HPD_NONE)
>> +                       enabled |= 1 << radeon_connector->hpd.hpd;
>>         }
>>         radeon_irq_kms_enable_hpd(rdev, enabled);
>>  }
>> @@ -1907,7 +1908,8 @@ void evergreen_hpd_fini(struct radeon_device *rdev)
>>                 default:
>>                         break;
>>                 }
>> -               disabled |= 1 << radeon_connector->hpd.hpd;
>> +               if (radeon_connector->hpd.hpd != RADEON_HPD_NONE)
>> +                       disabled |= 1 << radeon_connector->hpd.hpd;
>>         }
>>         radeon_irq_kms_disable_hpd(rdev, disabled);
>>  }
>> --
>> 2.7.3
>>
>> _______________________________________________
>> dri-devel mailing list
>> dri-devel@...ts.freedesktop.org
>> https://lists.freedesktop.org/mailman/listinfo/dri-devel

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