LoongArch: Fix access error when read fault on a write-only VMA

As with most architectures, allow handling of read faults in VMAs that
have VM_WRITE but without VM_READ (WRITE implies READ).

Otherwise, reading before writing a write-only memory will error while
reading after writing everything is fine.

BTW, move the VM_EXEC judgement before VM_READ/VM_WRITE to make logic a
little clearer.

Cc: stable@vger.kernel.org
Fixes: 09cfefb7fa70c3af01 ("LoongArch: Add memory management")
Signed-off-by: Jiantao Shan <shanjiantao@loongson.cn>
Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>

diff --git a/arch/loongarch/mm/fault.c b/arch/loongarch/mm/fault.c
index 1fc2f6813ea027d43ccf24af8aade31f1093df62..97b40defde060846d95c9bc02c70b13ec53372a7 100644 (file)
--- a/arch/loongarch/mm/fault.c
+++ b/arch/loongarch/mm/fault.c
@@ -202,10 +202,10 @@ good_area:
                if (!(vma->vm_flags & VM_WRITE))
                        goto bad_area;
        } else {
-               if (!(vma->vm_flags & VM_READ) && address != exception_era(regs))
-                       goto bad_area;
                if (!(vma->vm_flags & VM_EXEC) && address == exception_era(regs))
                        goto bad_area;
+               if (!(vma->vm_flags & (VM_READ | VM_WRITE)) && address != exception_era(regs))
+                       goto bad_area;
        }
 
        /*