Nicolai Stange <nicstange@xxxxxxxxx> 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 <nicstange@xxxxxxxxx> > --- > 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); > } _______________________________________________ dri-devel mailing list dri-devel@xxxxxxxxxxxxxxxxxxxxx https://lists.freedesktop.org/mailman/listinfo/dri-devel
