tree 87bdf3db6df2eb7d62327f1f761298223c756ae9
parent db196935d9562abec4510f48d887bc1f1e054fcf
author Alan Stern <stern@rowland.harvard.edu> 1439823762 -0400
committer James Bottomley <JBottomley@Odin.com> 1439910854 -0700

SCSI: Fix NULL pointer dereference in runtime PM

The routines in scsi_rpm.c assume that if a runtime-PM callback is
invoked for a SCSI device, it can only mean that the device's driver
has asked the block layer to handle the runtime power management (by
calling blk_pm_runtime_init(), which among other things sets q->dev).

However, this assumption turns out to be wrong for things like the ses
driver.  Normally ses devices are not allowed to do runtime PM, but
userspace can override this setting.  If this happens, the kernel gets
a NULL pointer dereference when blk_post_runtime_resume() tries to use
the uninitialized q->dev pointer.

This patch fixes the problem by calling the block layer's runtime-PM
routines only if the device's driver really does have a runtime-PM
callback routine.  Since ses doesn't define any such callbacks, the
crash won't occur.

This fixes Bugzilla #101371.

Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
Reported-by: Stanisław Pitucha <viraptor@gmail.com>
Reported-by: Ilan Cohen <ilanco@gmail.com>
Tested-by: Ilan Cohen <ilanco@gmail.com>
Reviewed-by: Johannes Thumshirn <jthumshirn@suse.de>
Cc: stable@vger.kernel.org
Signed-off-by: James Bottomley <JBottomley@Odin.com>