Merge branch 'security-fixes' into fixes

2 files changed, 47 insertions, 1 deletions

diff --git a/arch/arm/mm/Kconfig b/arch/arm/mm/Kconfig
index 6cacdc8dd654..db5c2cab8fda 100644
--- a/arch/arm/mm/Kconfig
+++ b/arch/arm/mm/Kconfig
@@ -421,24 +421,28 @@ config CPU_32v3
 	select CPU_USE_DOMAINS if MMU
 	select NEEDS_SYSCALL_FOR_CMPXCHG if SMP
 	select TLS_REG_EMUL if SMP || !MMU
+	select NEED_KUSER_HELPERS
 
 config CPU_32v4
 	bool
 	select CPU_USE_DOMAINS if MMU
 	select NEEDS_SYSCALL_FOR_CMPXCHG if SMP
 	select TLS_REG_EMUL if SMP || !MMU
+	select NEED_KUSER_HELPERS
 
 config CPU_32v4T
 	bool
 	select CPU_USE_DOMAINS if MMU
 	select NEEDS_SYSCALL_FOR_CMPXCHG if SMP
 	select TLS_REG_EMUL if SMP || !MMU
+	select NEED_KUSER_HELPERS
 
 config CPU_32v5
 	bool
 	select CPU_USE_DOMAINS if MMU
 	select NEEDS_SYSCALL_FOR_CMPXCHG if SMP
 	select TLS_REG_EMUL if SMP || !MMU
+	select NEED_KUSER_HELPERS
 
 config CPU_32v6
 	bool
@@ -776,6 +780,7 @@ config CPU_BPREDICT_DISABLE
 
 config TLS_REG_EMUL
 	bool
+	select NEED_KUSER_HELPERS
 	help
 	  An SMP system using a pre-ARMv6 processor (there are apparently
 	  a few prototypes like that in existence) and therefore access to
@@ -783,11 +788,40 @@ config TLS_REG_EMUL
 
 config NEEDS_SYSCALL_FOR_CMPXCHG
 	bool
+	select NEED_KUSER_HELPERS
 	help
 	  SMP on a pre-ARMv6 processor?  Well OK then.
 	  Forget about fast user space cmpxchg support.
 	  It is just not possible.
 
+config NEED_KUSER_HELPERS
+	bool
+
+config KUSER_HELPERS
+	bool "Enable kuser helpers in vector page" if !NEED_KUSER_HELPERS
+	default y
+	help
+	  Warning: disabling this option may break user programs.
+
+	  Provide kuser helpers in the vector page.  The kernel provides
+	  helper code to userspace in read only form at a fixed location
+	  in the high vector page to allow userspace to be independent of
+	  the CPU type fitted to the system.  This permits binaries to be
+	  run on ARMv4 through to ARMv7 without modification.
+
+	  However, the fixed address nature of these helpers can be used
+	  by ROP (return orientated programming) authors when creating
+	  exploits.
+
+	  If all of the binaries and libraries which run on your platform
+	  are built specifically for your platform, and make no use of
+	  these helpers, then you can turn this option off.  However,
+	  when such an binary or library is run, it will receive a SIGILL
+	  signal, which will terminate the program.
+
+	  Say N here only if you are absolutely certain that you do not
+	  need these helpers; otherwise, the safe option is to say Y.
+
 config DMA_CACHE_RWFO
 	bool "Enable read/write for ownership DMA cache maintenance"
 	depends on CPU_V6K && SMP
diff --git a/arch/arm/mm/mmu.c b/arch/arm/mm/mmu.c
index b3fdb63783e3..53cdbd39ec8e 100644
--- a/arch/arm/mm/mmu.c
+++ b/arch/arm/mm/mmu.c
@@ -1195,7 +1195,7 @@ static void __init devicemaps_init(struct machine_desc *mdesc)
 	/*
 	 * Allocate the vector page early.
 	 */
-	vectors = early_alloc(PAGE_SIZE);
+	vectors = early_alloc(PAGE_SIZE * 2);
 
 	early_trap_init(vectors);
 
@@ -1240,15 +1240,27 @@ static void __init devicemaps_init(struct machine_desc *mdesc)
 	map.pfn = __phys_to_pfn(virt_to_phys(vectors));
 	map.virtual = 0xffff0000;
 	map.length = PAGE_SIZE;
+#ifdef CONFIG_KUSER_HELPERS
 	map.type = MT_HIGH_VECTORS;
+#else
+	map.type = MT_LOW_VECTORS;
+#endif
 	create_mapping(&map);
 
 	if (!vectors_high()) {
 		map.virtual = 0;
+		map.length = PAGE_SIZE * 2;
 		map.type = MT_LOW_VECTORS;
 		create_mapping(&map);
 	}
 
+	/* Now create a kernel read-only mapping */
+	map.pfn += 1;
+	map.virtual = 0xffff0000 + PAGE_SIZE;
+	map.length = PAGE_SIZE;
+	map.type = MT_LOW_VECTORS;
+	create_mapping(&map);
+
 	/*
 	 * Ask the machine support to map in the statically mapped devices.
 	 */