[RFC v3 PATCH 5/5] x86: check VM_DEAD flag in page fault

[Yang Shi]

Check VM_DEAD flag of vma in page fault handler, if it is set, trigger
SIGSEGV.

Cc: Michal Hocko <mhocko@xxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxxxxx>
Cc: "H. Peter Anvin" <hpa@xxxxxxxxx>
Signed-off-by: Yang Shi <yang.shi@xxxxxxxxxxxxxxxxx>
---
 arch/x86/mm/fault.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/arch/x86/mm/fault.c b/arch/x86/mm/fault.c
index 9a84a0d..3fd2da5 100644
--- a/arch/x86/mm/fault.c
+++ b/arch/x86/mm/fault.c
@@ -1357,6 +1357,10 @@ static inline bool smap_violation(int error_code, struct pt_regs *regs)
 		bad_area(regs, error_code, address);
 		return;
 	}
+	if (unlikely(vma->vm_flags & VM_DEAD)) {
+		bad_area(regs, error_code, address);
+		return;
+	}
 	if (error_code & X86_PF_USER) {
 		/*
 		 * Accessing the stack below %sp is always a bug.
-- 
1.8.3.1