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? 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. Eric
