4.14-stable review patch. If anyone has any objections, please let me know.
------------------ From: Nicholas Piggin <npig...@gmail.com> commit 52396500f97c53860164debc7d4f759077853423 upstream. The SLB bad address handler's trap number fixup does not preserve the low bit that indicates nonvolatile GPRs have not been saved. This leads save_nvgprs to skip saving them, and subsequent functions and return from interrupt will think they are saved. This causes kernel branch-to-garbage debugging to not have correct registers, can also cause userspace to have its registers clobbered after a segfault. Fixes: f0f558b131db ("powerpc/mm: Preserve CFAR value on SLB miss caused by access to bogus address") Cc: sta...@vger.kernel.org # v4.9+ Signed-off-by: Nicholas Piggin <npig...@gmail.com> Signed-off-by: Michael Ellerman <m...@ellerman.id.au> Signed-off-by: Greg Kroah-Hartman <gre...@linuxfoundation.org> --- arch/powerpc/kernel/exceptions-64s.S | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) --- a/arch/powerpc/kernel/exceptions-64s.S +++ b/arch/powerpc/kernel/exceptions-64s.S @@ -704,7 +704,7 @@ EXC_COMMON_BEGIN(bad_addr_slb) ld r3, PACA_EXSLB+EX_DAR(r13) std r3, _DAR(r1) beq cr6, 2f - li r10, 0x480 /* fix trap number for I-SLB miss */ + li r10, 0x481 /* fix trap number for I-SLB miss */ std r10, _TRAP(r1) 2: bl save_nvgprs addi r3, r1, STACK_FRAME_OVERHEAD