From mboxrd@z Thu Jan  1 00:00:00 1970
From: Benjamin Herrenschmidt <benh@au1.ibm.com>
Subject: Re: [opensuse-factory] Re: [opensuse-kernel] libsigsegv build fail
 with kernel 3.18.3
Date: Mon, 02 Feb 2015 11:23:57 +1100
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To: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Max Filippov <jcmvbkbc@gmail.com>, Takashi Iwai <tiwai@suse.de>, "linux-arch@vger.kernel.org" <linux-arch@vger.kernel.org>, opensuse-factory@opensuse.org, OpenSUSE Kernel Team <opensuse-kernel@opensuse.org>

On Thu, 2015-01-29 at 10:16 -0800, Linus Torvalds wrote:
> diff --git a/arch/powerpc/mm/fault.c b/arch/powerpc/mm/fault.c
> index eb79907f34fa..6154b0a2b063 100644
> --- a/arch/powerpc/mm/fault.c
> +++ b/arch/powerpc/mm/fault.c
> @@ -437,6 +437,8 @@ good_area:
>          */
>         fault = handle_mm_fault(mm, vma, address, flags);
>         if (unlikely(fault & (VM_FAULT_RETRY|VM_FAULT_ERROR))) {
> +               if (fault & VM_FAULT_SIGSEGV)
> +                       goto bad_area;
>                 rc = mm_fault_error(regs, address, fault);
>                 if (rc >= MM_FAULT_RETURN)
>                         goto bail;

I prefer having the test inside mm_fault_error(), even if that makes the
patch a bit bigger, it keeps the logic in a single place. Untested
patch:

--- a/arch/powerpc/mm/fault.c
+++ b/arch/powerpc/mm/fault.c
@@ -184,6 +184,12 @@ static int mm_fault_error(struct pt_regs *regs, unsigned long addr, int fault)
 		return MM_FAULT_RETURN;
 	}
 
+	/* Other faults */
+
+	if (fault & VM_FAULT_SIGSEGV) {
+		up_read(&current->mm->mmap_sem);
+		return MM_FAULT_ERR(SIGSEGV);
+	}
 	if (fault & (VM_FAULT_SIGBUS|VM_FAULT_HWPOISON|VM_FAULT_HWPOISON_LARGE))
 		return do_sigbus(regs, addr, fault);
 


Cheers,
Ben.