On Wed, Aug 30, 2017 at 01:27:32PM -0700, Jerry Zhang wrote: > Hi, > > I'm running into a kernel crash while using the functionfs driver on > 4.9 and 4.12 kernels. This is reproducible by using any of the aio > syscalls with functionfs on the above kernels. The code in question is > in ffs_user_copy_worker, which is a work thread that copies a bit of > data into userspace. Interestingly, a set_fs(USER_DS) before > copy_to_iter in the work thread will prevent the crash. I'm told > though that this shouldn't be necessary if the thread does not set_fs > to KERNEL_DS, which it does not (nor does the rest of the driver, at > all). There is also no problem on 4.4. > > Perhaps this is related to some of the mm changes in arch/arm64 that > went in between 4.4 and 4.9? Alternatively, it could actually be > necessary to set_fs(USER_DS) in a work thread before accessing user > memory? Let us know. 4.4-4.9 is a long time, with a lot of changes :) Any chance you can run git bisect to find the issue? thanks, greg k-h -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
