On 25.09.2018 12:53, Arnd Bergmann wrote: > On Mon, Sep 17, 2018 at 9:46 PM Helge Deller <deller@xxxxxx> wrote: >> On 13.09.2018 17:59, Arnd Bergmann wrote: >>> There are only two 64-bit architecture ports that have a 32-bit >>> suseconds_t: sparc64 and parisc64. I've encountered a number of problems >>> with this, while trying to get a proper 64-bit time_t working on 32-bit >>> architectures. Having a 32-bit suseconds_t combined with a 64-bit time_t >>> means that we get extra padding in data structures that may leak kernel >>> stack data to user space, and it breaks all code that assumes that >>> timespec and timeval have the same layout. >>> >>> While we can't change sparc64, it seems that glibc on parisc64 has always >>> set suseconds_t to 'long', and the current version would give incorrect >>> results for gettimeofday() and many other interfaces: timestamps passed >>> from user space into the kernel result in tv_usec being always zero >>> (the lower bits contain the intended value but are ignored) while data >>> passed from the kernel to user space contains either zeroes or random >>> data in tv_usec. > > [back from traveling now, sorry for the delay in replying] > >> Should this wrong behavior be visible with 32-bit userspace or >> with 64-bit userspace (or both)? >> I didn't noticed such wrong behavior yet. > > Only 64-bit user space. > ... > A simple 64-bit gettimeofday() should report incorrect > nanoseconds using the upstream glibc implementation. Yes, you are right. Since we don't have any 64-bit userspace yet, it's safe to fix it now as you suggested. I've added your patch as is to my for-next tree and tagged it for stable-tree. Thanks for catching this! Helge
