From d61172b4b695b821388cdb6088a41d431bcbb93b Mon Sep 17 00:00:00 2001 From: Dave Hansen Date: Fri, 12 Feb 2016 13:02:24 -0800 Subject: mm/core, x86/mm/pkeys: Differentiate instruction fetches As discussed earlier, we attempt to enforce protection keys in software. However, the code checks all faults to ensure that they are not violating protection key permissions. It was assumed that all faults are either write faults where we check PKRU[key].WD (write disable) or read faults where we check the AD (access disable) bit. But, there is a third category of faults for protection keys: instruction faults. Instruction faults never run afoul of protection keys because they do not affect instruction fetches. So, plumb the PF_INSTR bit down in to the arch_vma_access_permitted() function where we do the protection key checks. We also add a new FAULT_FLAG_INSTRUCTION. This is because handle_mm_fault() is not passed the architecture-specific error_code where we keep PF_INSTR, so we need to encode the instruction fetch information in to the arch-generic fault flags. Signed-off-by: Dave Hansen Reviewed-by: Thomas Gleixner Cc: Andrew Morton Cc: Andy Lutomirski Cc: Borislav Petkov Cc: Brian Gerst Cc: Dave Hansen Cc: Denys Vlasenko Cc: H. Peter Anvin Cc: Linus Torvalds Cc: Peter Zijlstra Cc: Rik van Riel Cc: linux-mm@kvack.org Link: http://lkml.kernel.org/r/20160212210224.96928009@viggo.jf.intel.com Signed-off-by: Ingo Molnar --- mm/gup.c | 11 +++++++++-- mm/memory.c | 1 + 2 files changed, 10 insertions(+), 2 deletions(-) (limited to 'mm') diff --git a/mm/gup.c b/mm/gup.c index d276760163b3..7f1c4fb77cfa 100644 --- a/mm/gup.c +++ b/mm/gup.c @@ -449,7 +449,11 @@ static int check_vma_flags(struct vm_area_struct *vma, unsigned long gup_flags) if (!(vm_flags & VM_MAYREAD)) return -EFAULT; } - if (!arch_vma_access_permitted(vma, write, foreign)) + /* + * gups are always data accesses, not instruction + * fetches, so execute=false here + */ + if (!arch_vma_access_permitted(vma, write, false, foreign)) return -EFAULT; return 0; } @@ -629,8 +633,11 @@ bool vma_permits_fault(struct vm_area_struct *vma, unsigned int fault_flags) /* * The architecture might have a hardware protection * mechanism other than read/write that can deny access. + * + * gup always represents data access, not instruction + * fetches, so execute=false here: */ - if (!arch_vma_access_permitted(vma, write, foreign)) + if (!arch_vma_access_permitted(vma, write, false, foreign)) return false; return true; diff --git a/mm/memory.c b/mm/memory.c index 76c44e5dffa2..99e9f928264a 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -3380,6 +3380,7 @@ static int __handle_mm_fault(struct mm_struct *mm, struct vm_area_struct *vma, pte_t *pte; if (!arch_vma_access_permitted(vma, flags & FAULT_FLAG_WRITE, + flags & FAULT_FLAG_INSTRUCTION, flags & FAULT_FLAG_REMOTE)) return VM_FAULT_SIGSEGV; -- cgit v1.2.3