From d2cf909cda5f8c5609cb7ed6cda816c3e15528c7 Mon Sep 17 00:00:00 2001 From: Frederic Barrat Date: Fri, 17 Jun 2016 18:53:28 +0200 Subject: [PATCH] powerpc/mm: Prevent unlikely crash in copro_calculate_slb() If a cxl adapter faults on an invalid address for a kernel context, we may enter copro_calculate_slb() with a NULL mm pointer (kernel context) and an effective address which looks like a user address. Which will cause a crash when dereferencing mm. It is clearly an AFU bug, but there's no reason to crash either. So return an error, so that cxl can ack the interrupt with an address error. Fixes: 73d16a6e0e51 ("powerpc/cell: Move data segment faulting code out of cell platform") Cc: stable@vger.kernel.org # v3.18+ Signed-off-by: Frederic Barrat Acked-by: Ian Munsie Signed-off-by: Michael Ellerman --- arch/powerpc/mm/copro_fault.c | 2 ++ 1 file changed, 2 insertions(+) diff --git a/arch/powerpc/mm/copro_fault.c b/arch/powerpc/mm/copro_fault.c index bb0354222b11..362954f98029 100644 --- a/arch/powerpc/mm/copro_fault.c +++ b/arch/powerpc/mm/copro_fault.c @@ -106,6 +106,8 @@ int copro_calculate_slb(struct mm_struct *mm, u64 ea, struct copro_slb *slb) switch (REGION_ID(ea)) { case USER_REGION_ID: pr_devel("%s: 0x%llx -- USER_REGION_ID\n", __func__, ea); + if (mm == NULL) + return 1; psize = get_slice_psize(mm, ea); ssize = user_segment_size(ea); vsid = get_vsid(mm->context.id, ea, ssize); -- 2.20.1