Re: [PATCH] xhci: tegra: Prevent error pointer dereference

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On 20.2.2019 18.31, Greg Kroah-Hartman wrote:
On Wed, Feb 20, 2019 at 05:27:02PM +0100, Thierry Reding wrote:
On Wed, Feb 20, 2019 at 05:16:12PM +0100, Greg Kroah-Hartman wrote:
On Wed, Feb 20, 2019 at 02:48:41PM +0100, Thierry Reding wrote:
From: Thierry Reding <treding@xxxxxxxxxx>

During initialization, the host and super-speed power domains will
contain an ERR_PTR() encoded error code rather than being NULL. To
avoid a crash, use a !IS_ERR_OR_NULL() condition during cleanup.

Signed-off-by: Thierry Reding <treding@xxxxxxxxxx>
---
  drivers/usb/host/xhci-tegra.c | 4 ++--
  1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/usb/host/xhci-tegra.c b/drivers/usb/host/xhci-tegra.c
index 938ff06c0349..efb0cad8710e 100644
--- a/drivers/usb/host/xhci-tegra.c
+++ b/drivers/usb/host/xhci-tegra.c
@@ -941,9 +941,9 @@ static void tegra_xusb_powerdomain_remove(struct device *dev,
  		device_link_del(tegra->genpd_dl_ss);
  	if (tegra->genpd_dl_host)
  		device_link_del(tegra->genpd_dl_host);
-	if (tegra->genpd_dev_ss)
+	if (!IS_ERR_OR_NULL(tegra->genpd_dev_ss))
  		dev_pm_domain_detach(tegra->genpd_dev_ss, true);
-	if (tegra->genpd_dev_host)
+	if (!IS_ERR_OR_NULL(tegra->genpd_dev_host))
  		dev_pm_domain_detach(tegra->genpd_dev_host, true);
  }

Should this go to older kernels?  If so, any hint as to what commit this
"fixes:"?

Technically this:

Fixes: 6494a9ad86de ("usb: xhci: tegra: Add genpd support")

which was merged into v4.20.

However, I have never seen this actually crash on current kernels and
only came across it while working on a change to reset controls which
can cause dev_pm_domain_attach_by_name() to fail. That function can't
fail in current kernels, so I don't think we need to fix this in old
kernels. So if we can get this into v5.0, that'd be good enough for
me.

5.0-final is too late, but 5.0.y is doable.

Mathias, want me to take this directly?


Yes please

Acked-by: Mathias Nyman <mathias.nyman@xxxxxxxxxxxxxxx>





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