From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
From: Thomas Gleixner <tglx@linutronix.de>
Date: Thu, 14 Dec 2017 12:27:29 +0100
Subject: [PATCH] arch, mm: Allow arch_dup_mmap() to fail
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CVE-2017-5754

In order to sanitize the LDT initialization on x86 arch_dup_mmap() must be
allowed to fail. Fix up all instances.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Andy Lutomirsky <luto@kernel.org>
Cc: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Borislav Petkov <bpetkov@suse.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Dave Hansen <dave.hansen@intel.com>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: David Laight <David.Laight@aculab.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: Eduardo Valentin <eduval@amazon.com>
Cc: Greg KH <gregkh@linuxfoundation.org>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Juergen Gross <jgross@suse.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Will Deacon <will.deacon@arm.com>
Cc: aliguori@amazon.com
Cc: dan.j.williams@intel.com
Cc: hughd@google.com
Cc: keescook@google.com
Cc: kirill.shutemov@linux.intel.com
Cc: linux-mm@kvack.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
(cherry picked from commit c10e83f598d08046dd1ebc8360d4bb12d802d51b)
Signed-off-by: Andy Whitcroft <apw@canonical.com>
Signed-off-by: Kleber Sacilotto de Souza <kleber.souza@canonical.com>
(cherry picked from commit b812abb61437eda1f5718a95085d67902f813f2f)
Signed-off-by: Fabian Grünbichler <f.gruenbichler@proxmox.com>
---
 arch/powerpc/include/asm/mmu_context.h   | 5 +++--
 arch/um/include/asm/mmu_context.h        | 3 ++-
 arch/unicore32/include/asm/mmu_context.h | 5 +++--
 arch/x86/include/asm/mmu_context.h       | 4 ++--
 include/asm-generic/mm_hooks.h           | 5 +++--
 kernel/fork.c                            | 3 +--
 6 files changed, 14 insertions(+), 11 deletions(-)

diff --git a/arch/powerpc/include/asm/mmu_context.h b/arch/powerpc/include/asm/mmu_context.h
index 35bec1c5bd5a..60afcc94e673 100644
--- a/arch/powerpc/include/asm/mmu_context.h
+++ b/arch/powerpc/include/asm/mmu_context.h
@@ -185,9 +185,10 @@ static inline void enter_lazy_tlb(struct mm_struct *mm,
 #endif
 }
 
-static inline void arch_dup_mmap(struct mm_struct *oldmm,
-				 struct mm_struct *mm)
+static inline int arch_dup_mmap(struct mm_struct *oldmm,
+				struct mm_struct *mm)
 {
+	return 0;
 }
 
 static inline void arch_exit_mmap(struct mm_struct *mm)
diff --git a/arch/um/include/asm/mmu_context.h b/arch/um/include/asm/mmu_context.h
index b668e351fd6c..fca34b2177e2 100644
--- a/arch/um/include/asm/mmu_context.h
+++ b/arch/um/include/asm/mmu_context.h
@@ -15,9 +15,10 @@ extern void uml_setup_stubs(struct mm_struct *mm);
 /*
  * Needed since we do not use the asm-generic/mm_hooks.h:
  */
-static inline void arch_dup_mmap(struct mm_struct *oldmm, struct mm_struct *mm)
+static inline int arch_dup_mmap(struct mm_struct *oldmm, struct mm_struct *mm)
 {
 	uml_setup_stubs(mm);
+	return 0;
 }
 extern void arch_exit_mmap(struct mm_struct *mm);
 static inline void arch_unmap(struct mm_struct *mm,
diff --git a/arch/unicore32/include/asm/mmu_context.h b/arch/unicore32/include/asm/mmu_context.h
index 59b06b48f27d..5c205a9cb5a6 100644
--- a/arch/unicore32/include/asm/mmu_context.h
+++ b/arch/unicore32/include/asm/mmu_context.h
@@ -81,9 +81,10 @@ do { \
 	} \
 } while (0)
 
-static inline void arch_dup_mmap(struct mm_struct *oldmm,
-				 struct mm_struct *mm)
+static inline int arch_dup_mmap(struct mm_struct *oldmm,
+				struct mm_struct *mm)
 {
+	return 0;
 }
 
 static inline void arch_unmap(struct mm_struct *mm,
diff --git a/arch/x86/include/asm/mmu_context.h b/arch/x86/include/asm/mmu_context.h
index efc530642f7d..9be54d9c04c4 100644
--- a/arch/x86/include/asm/mmu_context.h
+++ b/arch/x86/include/asm/mmu_context.h
@@ -175,10 +175,10 @@ do {						\
 } while (0)
 #endif
 
-static inline void arch_dup_mmap(struct mm_struct *oldmm,
-				 struct mm_struct *mm)
+static inline int arch_dup_mmap(struct mm_struct *oldmm, struct mm_struct *mm)
 {
 	paravirt_arch_dup_mmap(oldmm, mm);
+	return 0;
 }
 
 static inline void arch_exit_mmap(struct mm_struct *mm)
diff --git a/include/asm-generic/mm_hooks.h b/include/asm-generic/mm_hooks.h
index 41e5b6784b97..7a2980f4e3e6 100644
--- a/include/asm-generic/mm_hooks.h
+++ b/include/asm-generic/mm_hooks.h
@@ -6,9 +6,10 @@
 #ifndef _ASM_GENERIC_MM_HOOKS_H
 #define _ASM_GENERIC_MM_HOOKS_H
 
-static inline void arch_dup_mmap(struct mm_struct *oldmm,
-				 struct mm_struct *mm)
+static inline int arch_dup_mmap(struct mm_struct *oldmm,
+				struct mm_struct *mm)
 {
+	return 0;
 }
 
 static inline void arch_exit_mmap(struct mm_struct *mm)
diff --git a/kernel/fork.c b/kernel/fork.c
index 8efc6b4466e3..1d907772b9d2 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -712,8 +712,7 @@ static __latent_entropy int dup_mmap(struct mm_struct *mm,
 			goto out;
 	}
 	/* a new mm has just been created */
-	arch_dup_mmap(oldmm, mm);
-	retval = 0;
+	retval = arch_dup_mmap(oldmm, mm);
 out:
 	up_write(&mm->mmap_sem);
 	flush_tlb_mm(oldmm);
-- 
2.14.2

