linux-kernel - drm/gma500: Possible deadlock in gma_power

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [thread-next>] [day] [month] [year] [list]

Date:	Sat, 28 Feb 2015 18:02:33 +0300
From:	Alexey Khoroshilov <khoroshilov@...ras.ru>
To:	Patrik Jakobsson <patrik.r.jakobsson@...il.com>,
	David Airlie <airlied@...ux.ie>
CC:	dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org,
	ldv-project@...uxtesting.org
Subject: drm/gma500: Possible deadlock in gma_power_begin()

gma_power_begin() starts with locking power_ctrl_lock spinlock and then,
if gma_resume_pci(dev->pdev) succeed, it calls
  psb_irq_preinstall(dev);
  psb_irq_postinstall(dev);

psb_irq_postinstall() does some pipestat enabling/disabling dance:
    if (dev->vblank[0].enabled)
        psb_enable_pipestat(dev_priv, 0, PIPE_VBLANK_INTERRUPT_ENABLE);
    else
        psb_disable_pipestat(dev_priv, 0, PIPE_VBLANK_INTERRUPT_ENABLE);

where
void psb_enable_pipestat(struct drm_psb_private *dev_priv, int pipe, u32
mask)
{
    if ((dev_priv->pipestat[pipe] & mask) != mask) {
        u32 reg = psb_pipestat(pipe);
        dev_priv->pipestat[pipe] |= mask;
        /* Enable the interrupt, clear any pending status */
        if (gma_power_begin(dev_priv->dev, false)) {
            u32 writeVal = PSB_RVDC32(reg);
            writeVal |= (mask | (mask >> 16));
            PSB_WVDC32(writeVal, reg);
            (void) PSB_RVDC32(reg);
            gma_power_end(dev_priv->dev);
        }
    }
}

So, if a flag in dev_priv->pipestat[pipe] is not in agreement with
dev->vblank[0].enabled,
we will have a call to gma_power_begin() again and got an unavoidable
deadlock.

Thus it seems either some code is unneeded at all or we could have a
deadlock from time to time.
What do you think?

Found by Linux Driver Verification project (linuxtesting.org).

--
Alexey Khoroshilov
Linux Verification Center, ISPRAS

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/