Russell King - ARM Linux <linux@xxxxxxxxxxxxxxx> writes: > On Thu, Jan 11, 2018 at 06:59:37PM -0600, Eric W. Biederman wrote: >> Setting si_code to 0 results in a userspace seeing an si_code of 0. >> This is the same si_code as SI_USER. Posix and common sense requires >> that SI_USER not be a signal specific si_code. As such this use of 0 >> for the si_code is a pretty horribly broken ABI. >> >> Further use of si_code == 0 guaranteed that copy_siginfo_to_user saw a >> value of __SI_KILL and now sees a value of SIL_KILL with the result >> that uid and pid fields are copied and which might copying the si_addr >> field by accident but certainly not by design. Making this a very >> flakey implementation. >> >> Utilizing FPE_FIXME, siginfo_layout will now return SIL_FAULT and the >> appropriate fields will be reliably copied. > > So what do you suggest when none of the SIGFPE FPE_xxx codes match the > condition that "we don't know what happened" ? Raise a SIGKILL instead > maybe? We will have dumped the VFP state into the kernel log at this > point, things are pretty much fscked. > > It's probably an impossible condition unless the hardware has failed, > no one has knowingly reported getting such a dump in their kernel log, > so it's something that could very likely be changed in some way > without anyone noticing. It sounds like we have two equally valid possible solutions: 1) force_sig(SIGKILL, current); 2) Allocate a new FPE_xxx code in asm-generic/siginfo.h I believe the next available number is 15. If no one is going to notice this should be comparatively easy to fix. I just don't have the knowledge of arm to make the judgement myself. Eric
