On 23.02.2018 01:15, Eric W. Biederman wrote: > Helge Deller <deller@xxxxxx> writes: > >> * Eric W. Biederman <ebiederm@xxxxxxxxxxxx>: >>> 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 reliably be copied. >>> >>> This bug is 13 years old and parsic machines are no longer being built >>> so I don't know if it possible or worth fixing it. But it is at least >>> worth documenting this so other architectures don't make the same >>> mistake. >> >> >> I think we should fix it, even if we now break the ABI. >> >> It's about a "conditional trap" which needs to be handled by userspace. >> I doubt there is any Linux code out which is utilizing this >> parisc-specific trap. >> >> I'd suggest to add a new FPE trap si_code (e.g. FPE_CONDTRAP). >> While at it, maybe we should include the already existing FPE_MDAOVF >> from the frv architecture, so that arch/frv/include/uapi/asm/siginfo.h >> can go completely. >> >> Suggested patch is below. >> >> I'm willing to test the patch below on the parisc architecture for a few >> weeks. And it will break arch/x86/kernel/signal_compat.c which needs >> looking at then too. > > Have you managed to test this change? Sadly I haven't done any further testing yet. > I am sitting looking at another new FPE si_code and if this has been tested > I figure FPE_CONDTRAP should get the next available FPE si_code and the > other change should get the one that follows. I'm fine either way. Do you have a git tree I can pull which includes all your patches? I can then start testing. Helge
