[PATCH] arm: cmpxchg syscall should data abort if page not write or not young

[Po-Yu Chuang <ratbert.chuang@gmail.com>]

From: Po-Yu Chuang <ratbert@faraday-tech.com>

If the page to cmpxchg is user mode read only (not write)
or invalid (not young), we should simulate a data abort first.

Signed-off-by: Po-Yu Chuang <ratbert@faraday-tech.com>
---
 arch/arm/kernel/traps.c |    3 ++-
 1 files changed, 2 insertions(+), 1 deletions(-)

diff --git a/arch/arm/kernel/traps.c b/arch/arm/kernel/traps.c
index 446aee9..53c8852 100644
--- a/arch/arm/kernel/traps.c
+++ b/arch/arm/kernel/traps.c
@@ -563,7 +563,8 @@ asmlinkage int arm_syscall(int no, struct pt_regs *regs)
 		if (!pmd_present(*pmd))
 			goto bad_access;
 		pte = pte_offset_map_lock(mm, pmd, addr, &ptl);
-		if (!pte_present(*pte) || !pte_dirty(*pte)) {
+		if (!pte_present(*pte) || !pte_write(*pte) ||
+		    !pte_dirty(*pte) || !pte_young(*pte)) {
 			pte_unmap_unlock(pte, ptl);
 			goto bad_access;
 		}
-- 
1.6.3.3