linux-kernel - [PATCH v7 08/12] powerpc/fsl_booke/kaslr: clear the original kernel if randomized

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Date:   Fri, 20 Sep 2019 17:45:42 +0800
From:   Jason Yan <yanaijie@...wei.com>
To:     <mpe@...erman.id.au>, <linuxppc-dev@...ts.ozlabs.org>,
        <diana.craciun@....com>, <christophe.leroy@....fr>,
        <benh@...nel.crashing.org>, <paulus@...ba.org>,
        <npiggin@...il.com>, <keescook@...omium.org>,
        <kernel-hardening@...ts.openwall.com>
CC:     <linux-kernel@...r.kernel.org>, <wangkefeng.wang@...wei.com>,
        <yebin10@...wei.com>, <thunder.leizhen@...wei.com>,
        <jingxiangfeng@...wei.com>, <zhaohongjiang@...wei.com>,
        <oss@...error.net>, Jason Yan <yanaijie@...wei.com>
Subject: [PATCH v7 08/12] powerpc/fsl_booke/kaslr: clear the original kernel if randomized

The original kernel still exists in the memory, clear it now.

Signed-off-by: Jason Yan <yanaijie@...wei.com>
Cc: Diana Craciun <diana.craciun@....com>
Cc: Michael Ellerman <mpe@...erman.id.au>
Cc: Christophe Leroy <christophe.leroy@....fr>
Cc: Benjamin Herrenschmidt <benh@...nel.crashing.org>
Cc: Paul Mackerras <paulus@...ba.org>
Cc: Nicholas Piggin <npiggin@...il.com>
Cc: Kees Cook <keescook@...omium.org>
Reviewed-by: Christophe Leroy <christophe.leroy@....fr>
Reviewed-by: Diana Craciun <diana.craciun@....com>
Tested-by: Diana Craciun <diana.craciun@....com>
---
 arch/powerpc/mm/mmu_decl.h           |  2 ++
 arch/powerpc/mm/nohash/fsl_booke.c   |  1 +
 arch/powerpc/mm/nohash/kaslr_booke.c | 11 +++++++++++
 3 files changed, 14 insertions(+)

diff --git a/arch/powerpc/mm/mmu_decl.h b/arch/powerpc/mm/mmu_decl.h
index a3a4937c0496..565731475a07 100644
--- a/arch/powerpc/mm/mmu_decl.h
+++ b/arch/powerpc/mm/mmu_decl.h
@@ -151,8 +151,10 @@ extern void loadcam_multi(int first_idx, int num, int tmp_idx);
 
 #ifdef CONFIG_RANDOMIZE_BASE
 void kaslr_early_init(void *dt_ptr, phys_addr_t size);
+void kaslr_late_init(void);
 #else
 static inline void kaslr_early_init(void *dt_ptr, phys_addr_t size) {}
+static inline void kaslr_late_init(void) {}
 #endif
 
 struct tlbcam {
diff --git a/arch/powerpc/mm/nohash/fsl_booke.c b/arch/powerpc/mm/nohash/fsl_booke.c
index 2dc27cf88add..b4eb06ceb189 100644
--- a/arch/powerpc/mm/nohash/fsl_booke.c
+++ b/arch/powerpc/mm/nohash/fsl_booke.c
@@ -269,6 +269,7 @@ notrace void __init relocate_init(u64 dt_ptr, phys_addr_t start)
 	kernstart_addr = start;
 	if (is_second_reloc) {
 		virt_phys_offset = PAGE_OFFSET - memstart_addr;
+		kaslr_late_init();
 		return;
 	}
 
diff --git a/arch/powerpc/mm/nohash/kaslr_booke.c b/arch/powerpc/mm/nohash/kaslr_booke.c
index 7b238fc2c8a9..aa1b60c782e7 100644
--- a/arch/powerpc/mm/nohash/kaslr_booke.c
+++ b/arch/powerpc/mm/nohash/kaslr_booke.c
@@ -381,3 +381,14 @@ notrace void __init kaslr_early_init(void *dt_ptr, phys_addr_t size)
 
 	reloc_kernel_entry(dt_ptr, kernstart_virt_addr);
 }
+
+void __init kaslr_late_init(void)
+{
+	/* If randomized, clear the original kernel */
+	if (kernstart_virt_addr != KERNELBASE) {
+		unsigned long kernel_sz;
+
+		kernel_sz = (unsigned long)_end - kernstart_virt_addr;
+		memzero_explicit((void *)KERNELBASE, kernel_sz);
+	}
+}
-- 
2.17.2