On 11/30/2015 11:45 PM, Ken Xue wrote:
The routines in scsi_pm.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 checking q->dev in block layer before handle runtime PM. Since ses doesn't define any PM callbacks and call blk_pm_runtime_init(), the crash won't occur. This fixes Bugzilla #101371. https://bugzilla.kernel.org/show_bug.cgi?id=101371 More discussion can be found from below link. http://marc.info/?l=linux-scsi&m=144163730531875&w=2
Added for 4.4, thanks. -- Jens Axboe -- To unsubscribe from this list: send the line "unsubscribe linux-block" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
