From f138556daf62665f19178732ec4daf86c4ca13f4 Mon Sep 17 00:00:00 2001 From: Piotr Kwapulinski Date: Tue, 22 Mar 2016 14:27:51 -0700 Subject: [PATCH] mm/mprotect.c: don't imply PROT_EXEC on non-exec fs The mprotect(PROT_READ) fails when called by the READ_IMPLIES_EXEC binary on a memory mapped file located on non-exec fs. The mprotect does not check whether fs is _executable_ or not. The PROT_EXEC flag is set automatically even if a memory mapped file is located on non-exec fs. Fix it by checking whether a memory mapped file is located on a non-exec fs. If so the PROT_EXEC is not implied by the PROT_READ. The implementation uses the VM_MAYEXEC flag set properly in mmap. Now it is consistent with mmap. I did the isolated tests (PT_GNU_STACK X/NX, multiple VMAs, X/NX fs). I also patched the official 3.19.0-47-generic Ubuntu 14.04 kernel and it seems to work. Signed-off-by: Piotr Kwapulinski Cc: Mel Gorman Cc: Kirill A. Shutemov Cc: Aneesh Kumar K.V Cc: Benjamin Herrenschmidt Cc: Konstantin Khlebnikov Cc: Dan Williams Cc: Dave Hansen Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- mm/mprotect.c | 13 ++++++++----- 1 file changed, 8 insertions(+), 5 deletions(-) diff --git a/mm/mprotect.c b/mm/mprotect.c index fa37c4c..b650c54 100644 --- a/mm/mprotect.c +++ b/mm/mprotect.c @@ -359,6 +359,9 @@ SYSCALL_DEFINE3(mprotect, unsigned long, start, size_t, len, struct vm_area_struct *vma, *prev; int error = -EINVAL; const int grows = prot & (PROT_GROWSDOWN|PROT_GROWSUP); + const bool rier = (current->personality & READ_IMPLIES_EXEC) && + (prot & PROT_READ); + prot &= ~(PROT_GROWSDOWN|PROT_GROWSUP); if (grows == (PROT_GROWSDOWN|PROT_GROWSUP)) /* can't be both */ return -EINVAL; @@ -375,11 +378,6 @@ SYSCALL_DEFINE3(mprotect, unsigned long, start, size_t, len, return -EINVAL; reqprot = prot; - /* - * Does the application expect PROT_READ to imply PROT_EXEC: - */ - if ((prot & PROT_READ) && (current->personality & READ_IMPLIES_EXEC)) - prot |= PROT_EXEC; down_write(¤t->mm->mmap_sem); @@ -414,6 +412,10 @@ SYSCALL_DEFINE3(mprotect, unsigned long, start, size_t, len, /* Here we know that vma->vm_start <= nstart < vma->vm_end. */ + /* Does the application expect PROT_READ to imply PROT_EXEC */ + if (rier && (vma->vm_flags & VM_MAYEXEC)) + prot |= PROT_EXEC; + newflags = calc_vm_prot_bits(prot, pkey); newflags |= (vma->vm_flags & ~(VM_READ | VM_WRITE | VM_EXEC)); @@ -445,6 +447,7 @@ SYSCALL_DEFINE3(mprotect, unsigned long, start, size_t, len, error = -ENOMEM; goto out; } + prot = reqprot; } out: up_write(¤t->mm->mmap_sem); -- 2.7.4