Changes since RFC v2: * Fold in reverts of the relevant parts of Eric's *_FIXME changes, since this series removes all cases of those dummy si_code values from arm64. * Propagated the new signal/si_code assignments for synchronous external aborts correctly to signals thrown from do_sea(). Original blurb: As reported by Eric Biederman, [1], [2], [3] etc., several architectures are inappropriately setting si_code to 0 when signaling faults to userspace, which will interpret this value as SI_USER leading to garbage being read out of siginfo fields that the kernel doesn't initialise. This seems not to be a huge problem in practice, since many affected faults should only happen if the kernel or hardware is buggy or broken. However, there are some cases that don't fall under this. This RFC series proposes fixes to eliminate these si_code == 0 cases from arm64. Some of the changes may be controversial. There are two main headlines here, which may be applicable to other architectures: * addition of a new code FPE_UNKNOWN for undiagnosable floating-point exception traps; * delivering SIGKILL instead of SIGSEGV/BUS/TRAP etc. for "impossible" exceptions that are not feasible to recover from and likely indicate a kernel or system bug or failure. In particular there is likely to be a fair amount of overlap between arm and arm64 here, but due to the longer history and evolution of the arm tree and 32-bit architecture I'm less confident in making correct judgements for that case. This series doesn't touch arm, for now. Boot-tested on Arm Juno r0. Floating-point exception traps tested on the Arm Fast Model. [1] [PATCH 00/11] siginfo fixes/cleanups esp SI_USER https://marc.info/?l=linux-kernel&m=151571871109016&w=2 [2] [PATCH 08/11] signal/arm: Document conflicts with SI_USER and SIGFPE http://lists.infradead.org/pipermail/linux-arm-kernel/2018-January/553574.html [3] [PATCH 07/11] signal/arm64: Document conflicts with SI_USER and SIGFPE, SIGTRAP, SIGBUS lists.infradead.org/pipermail/linux-arm-kernel/2018-January/553573.html --- Dave Martin (3): signal: Add FPE_FLTUNK si_code for undiagnosable fp exceptions arm64: fpsimd: Fix bad si_code for undiagnosed SIGFPE arm64: signal: Ensure si_code is valid for all fault signals arch/arm64/include/asm/esr.h | 9 +++ arch/arm64/include/uapi/asm/siginfo.h | 21 ------ arch/arm64/kernel/fpsimd.c | 31 +++++---- arch/arm64/mm/fault.c | 116 +++++++++++++++++----------------- include/uapi/asm-generic/siginfo.h | 3 +- kernel/signal.c | 4 -- 6 files changed, 86 insertions(+), 98 deletions(-) -- 2.1.4 -- To unsubscribe from this list: send the line "unsubscribe linux-api" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
