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
The net effect is that radeon_irq_kms_enable_hpd() enables the HPD
interrupts for all HPD pins in the range from 0 to RADEON_MAX_HPD_PINS.
The system seems to work without any noticeable glitches though.
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 <[email protected]>
---
Applicable to linux-next-20160318.
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
Nicolai Stange <[email protected]> writes:
> 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
>
> The net effect is that radeon_irq_kms_enable_hpd() enables the HPD
> interrupts for all HPD pins in the range from 0 to RADEON_MAX_HPD_PINS.
And this is obviously wrong: I mixed the shift count 0xff with the final
value when reasoning about the implications :(
1 << 0xff == 1 << 0x1f == 2^31 on x86 at least. Thus the net effect is
nothing.
I will resend later this day with an updated description.
> The system seems to work without any noticeable glitches though.
>
> 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 <[email protected]>
> ---
> Applicable to linux-next-20160318.
>
> 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);
> }