linux-kernel - [PATCH] riscv: read-only pages should not be writable

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Message-Id: <20220528014132.91052-1-heinrich.schuchardt@canonical.com>
Date:   Sat, 28 May 2022 03:41:32 +0200
From:   Heinrich Schuchardt <heinrich.schuchardt@...onical.com>
To:     Ard Biesheuvel <ardb@...nel.org>
Cc:     Paul Walmsley <paul.walmsley@...ive.com>,
        Palmer Dabbelt <palmer@...belt.com>,
        Albert Ou <aou@...s.berkeley.edu>,
        Atish Patra <atishp@...shpatra.org>, linux-efi@...r.kernel.org,
        linux-riscv@...ts.infradead.org, linux-kernel@...r.kernel.org,
        Heinrich Schuchardt <heinrich.schuchardt@...onical.com>
Subject: [PATCH] riscv: read-only pages should not be writable

If EFI pages are marked as read-only,
we should remove the _PAGE_WRITE flag.

The current code overwrites an unused value.

Fixes: b91540d52a08b ("RISC-V: Add EFI runtime services")
Signed-off-by: Heinrich Schuchardt <heinrich.schuchardt@...onical.com>
---
 arch/riscv/kernel/efi.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/riscv/kernel/efi.c b/arch/riscv/kernel/efi.c
index 024159298231..1aa540350abd 100644
--- a/arch/riscv/kernel/efi.c
+++ b/arch/riscv/kernel/efi.c
@@ -65,7 +65,7 @@ static int __init set_permissions(pte_t *ptep, unsigned long addr, void *data)
 
 	if (md->attribute & EFI_MEMORY_RO) {
 		val = pte_val(pte) & ~_PAGE_WRITE;
-		val = pte_val(pte) | _PAGE_READ;
+		val |= _PAGE_READ;
 		pte = __pte(val);
 	}
 	if (md->attribute & EFI_MEMORY_XP) {
-- 
2.36.1