linux-kernel - [PATCH 4.18 37/44] powerpc/lib: fix book3s/32 boot failure due to code patching

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Date:   Thu, 11 Oct 2018 17:40:15 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Christophe Leroy <christophe.leroy@....fr>,
        Michael Ellerman <mpe@...erman.id.au>
Subject: [PATCH 4.18 37/44] powerpc/lib: fix book3s/32 boot failure due to code patching

4.18-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Christophe Leroy <christophe.leroy@....fr>

commit b45ba4a51cde29b2939365ef0c07ad34c8321789 upstream.

Commit 51c3c62b58b3 ("powerpc: Avoid code patching freed init
sections") accesses 'init_mem_is_free' flag too early, before the
kernel is relocated. This provokes early boot failure (before the
console is active).

As it is not necessary to do this verification that early, this
patch moves the test into patch_instruction() instead of
__patch_instruction().

This modification also has the advantage of avoiding unnecessary
remappings.

Fixes: 51c3c62b58b3 ("powerpc: Avoid code patching freed init sections")
Cc: stable@...r.kernel.org # 4.13+
Signed-off-by: Christophe Leroy <christophe.leroy@....fr>
Signed-off-by: Michael Ellerman <mpe@...erman.id.au>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 arch/powerpc/lib/code-patching.c |   20 ++++++++++++--------
 1 file changed, 12 insertions(+), 8 deletions(-)

--- a/arch/powerpc/lib/code-patching.c
+++ b/arch/powerpc/lib/code-patching.c
@@ -28,12 +28,6 @@ static int __patch_instruction(unsigned
 {
 	int err;
 
-	/* Make sure we aren't patching a freed init section */
-	if (init_mem_is_free && init_section_contains(exec_addr, 4)) {
-		pr_debug("Skipping init section patching addr: 0x%px\n", exec_addr);
-		return 0;
-	}
-
 	__put_user_size(instr, patch_addr, 4, err);
 	if (err)
 		return err;
@@ -148,7 +142,7 @@ static inline int unmap_patch_area(unsig
 	return 0;
 }
 
-int patch_instruction(unsigned int *addr, unsigned int instr)
+static int do_patch_instruction(unsigned int *addr, unsigned int instr)
 {
 	int err;
 	unsigned int *patch_addr = NULL;
@@ -188,12 +182,22 @@ out:
 }
 #else /* !CONFIG_STRICT_KERNEL_RWX */
 
-int patch_instruction(unsigned int *addr, unsigned int instr)
+static int do_patch_instruction(unsigned int *addr, unsigned int instr)
 {
 	return raw_patch_instruction(addr, instr);
 }
 
 #endif /* CONFIG_STRICT_KERNEL_RWX */
+
+int patch_instruction(unsigned int *addr, unsigned int instr)
+{
+	/* Make sure we aren't patching a freed init section */
+	if (init_mem_is_free && init_section_contains(addr, 4)) {
+		pr_debug("Skipping init section patching addr: 0x%px\n", addr);
+		return 0;
+	}
+	return do_patch_instruction(addr, instr);
+}
 NOKPROBE_SYMBOL(patch_instruction);
 
 int patch_branch(unsigned int *addr, unsigned long target, int flags)