From: Dave Hansen dave.hansen@linux.intel.com

mm_pkey_is_allocated() treats pkey 0 as unallocated. That is inconsistent with the manpages, and also inconsistent with mm->context.pkey_allocation_map. Stop special casing it and only disallow values that are actually bad (< 0).

The end-user visible effect of this is that you can now use mprotect_pkey() to set pkey=0.

This is a bit nicer than what Ram proposed because it is simpler and removes special-casing for pkey 0. On the other hand, it does allow applciations to pkey_free() pkey-0, but that's just a silly thing to do, so we are not going to protect against it.

Signed-off-by: Dave Hansen dave.hansen@linux.intel.com Fixes: 58ab9a088dda ("x86/pkeys: Check against max pkey to avoid overflows") Cc: stable@kernel.org Cc: Ram Pai linuxram@us.ibm.com Cc: Thomas Gleixner tglx@linutronix.de Cc: Dave Hansen dave.hansen@intel.com Cc: Michael Ellermen mpe@ellerman.id.au Cc: Ingo Molnar mingo@kernel.org Cc: Andrew Morton akpm@linux-foundation.orgp Cc: Shuah Khan shuah@kernel.org ---

b/arch/x86/include/asm/mmu_context.h | 2 +- b/arch/x86/include/asm/pkeys.h | 6 +++--- 2 files changed, 4 insertions(+), 4 deletions(-)

diff -puN arch/x86/include/asm/mmu_context.h~x86-pkey-0-default-allocated arch/x86/include/asm/mmu_context.h --- a/arch/x86/include/asm/mmu_context.h~x86-pkey-0-default-allocated 2018-03-26 10:22:33.742170197 -0700 +++ b/arch/x86/include/asm/mmu_context.h 2018-03-26 10:22:33.747170197 -0700 @@ -192,7 +192,7 @@ static inline int init_new_context(struc

#ifdef CONFIG_X86_INTEL_MEMORY_PROTECTION_KEYS if (cpu_feature_enabled(X86_FEATURE_OSPKE)) { - /* pkey 0 is the default and always allocated */ + /* pkey 0 is the default and allocated implicitly */ mm->context.pkey_allocation_map = 0x1; /* -1 means unallocated or invalid */ mm->context.execute_only_pkey = -1; diff -puN arch/x86/include/asm/pkeys.h~x86-pkey-0-default-allocated arch/x86/include/asm/pkeys.h --- a/arch/x86/include/asm/pkeys.h~x86-pkey-0-default-allocated 2018-03-26 10:22:33.744170197 -0700 +++ b/arch/x86/include/asm/pkeys.h 2018-03-26 10:22:33.747170197 -0700 @@ -49,10 +49,10 @@ bool mm_pkey_is_allocated(struct mm_stru { /* * "Allocated" pkeys are those that have been returned - * from pkey_alloc(). pkey 0 is special, and never - * returned from pkey_alloc(). + * from pkey_alloc() or pkey 0 which is allocated + * implicitly when the mm is created. */ - if (pkey <= 0) + if (pkey < 0) return false; if (pkey >= arch_max_pkey()) return false; _