[PATCH v2] riscv: mm: Ensure prot of VM_WRITE and VM_EXEC must be readable

[Woodrow Shen]

From: Hsieh-Tseng Shen <woodrow.shen at sifive.com>

Commit 8aeb7b17f04e ("RISC-V: Make mmap() with PROT_WRITE imply PROT_READ")
allows riscv to use mmap with PROT_WRITE only, and meanwhile mmap with w+x
is also permitted. However, when userspace tries to access this page with
PROT_WRITE|PROT_EXEC, which causes infinite loop at load page fault as
well as it triggers soft lockup. According to riscv privileged spec,
"Writable pages must also be marked readable". The fix to drop the
`PAGE_COPY_READ_EXEC` and then `PAGE_COPY_EXEC` would be just used instead.
This aligns the other arches (i.e arm64) for protection_map.

Fixes: 8aeb7b17f04e ("RISC-V: Make mmap() with PROT_WRITE imply PROT_READ")
Signed-off-by: Hsieh-Tseng Shen <woodrow.shen at sifive.com>
Reviewed-by: Alexandre Ghiti <alexghiti at rivosinc.com>
---
Changelog V2:
 - Rename PAGE_COPY_READ_EXEC into PAGE_COPY_EXEC and remove
   PAGE_COPY_READ_EXEC.
---
 arch/riscv/include/asm/pgtable.h | 3 +--
 arch/riscv/mm/init.c             | 2 +-
 2 files changed, 2 insertions(+), 3 deletions(-)

diff --git a/arch/riscv/include/asm/pgtable.h b/arch/riscv/include/asm/pgtable.h
index f641837ccf31..05eda3281ba9 100644
--- a/arch/riscv/include/asm/pgtable.h
+++ b/arch/riscv/include/asm/pgtable.h
@@ -165,8 +165,7 @@ extern struct pt_alloc_ops pt_ops __initdata;
 					 _PAGE_EXEC | _PAGE_WRITE)
 
 #define PAGE_COPY		PAGE_READ
-#define PAGE_COPY_EXEC		PAGE_EXEC
-#define PAGE_COPY_READ_EXEC	PAGE_READ_EXEC
+#define PAGE_COPY_EXEC		PAGE_READ_EXEC
 #define PAGE_SHARED		PAGE_WRITE
 #define PAGE_SHARED_EXEC	PAGE_WRITE_EXEC
 
diff --git a/arch/riscv/mm/init.c b/arch/riscv/mm/init.c
index 0f14f4a8d179..cc48b0d93a98 100644
--- a/arch/riscv/mm/init.c
+++ b/arch/riscv/mm/init.c
@@ -286,7 +286,7 @@ static const pgprot_t protection_map[16] = {
 	[VM_EXEC]					= PAGE_EXEC,
 	[VM_EXEC | VM_READ]				= PAGE_READ_EXEC,
 	[VM_EXEC | VM_WRITE]				= PAGE_COPY_EXEC,
-	[VM_EXEC | VM_WRITE | VM_READ]			= PAGE_COPY_READ_EXEC,
+	[VM_EXEC | VM_WRITE | VM_READ]			= PAGE_COPY_EXEC,
 	[VM_SHARED]					= PAGE_NONE,
 	[VM_SHARED | VM_READ]				= PAGE_READ,
 	[VM_SHARED | VM_WRITE]				= PAGE_SHARED,
-- 
2.34.1