On Tue, Feb 24, 2015 at 04:54:17PM -0500, Chris Metcalf wrote: > On 2/14/2015 6:22 AM, Catalin Marinas wrote: > >1. user populates sival_int compat_sigevent and invokes > > compat_sys_mq_notify() > >2. kernel get_compat_sigevent() copies compat_sigevent into the native > > sigevent. compat and native sival_int are the same, no problem so > > far. The other half of 64-bit sival_ptr is zeroed by a memset in this > > function (this other half can be top or bottom, depending on > > endianness) > >3. signal is about to be delivered to user via arch code. The > > compat_ptr(from->si_ptr) conversion always takes the least > > significant part of the native si_ptr. On big endian 64-bit, this is > > zero because get_compat_sigevent() populated the top part of si_ptr > > with si_int. > > > >So delivering such signals to compat user always sets si_int to 0. > >Little endian is fine. > > I looked at this again as I was getting ready to do a tile patch, and realized > why tile and arm64 are different here: tile does a field-by-field copy in > copy_siginfo_from_user32(), like parisc and s390. As a result, we initialize > the 64-bit kernel si_ptr value by cast from the 32-bit user si_ptr value, rather > than blindly writing into the lower-addressed half of the 64-bit sigval. It's not about copy_siginfo_from_user32() but the generic get_compat_sigevent() which always uses sival_int (called from e.g. compat_sys_timer_create()). -- Catalin -- To unsubscribe from this list: send the line "unsubscribe linux-arch" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
