[RFC/PATCH 1/8] revoke: special mmap handling V7 From: Pekka Enberg This adds special handling for revoked shared memory mappings. We want to raise SIGBUS if someone accesses a revoked mapping and return ENODEV if somebody tries to remap one with mmap(2). Cc: Alan Cox Cc: Al Viro Cc: Christoph Hellwig Cc: Peter Zijlstra Signed-off-by: Pekka Enberg --- include/linux/mm.h | 1 + mm/memory.c | 3 +++ mm/mmap.c | 12 ++++++++---- 3 files changed, 12 insertions(+), 4 deletions(-) Index: 2.6/include/linux/mm.h =================================================================== --- 2.6.orig/include/linux/mm.h 2007-12-14 11:33:57.000000000 +0200 +++ 2.6/include/linux/mm.h 2007-12-14 16:40:48.000000000 +0200 @@ -106,6 +106,7 @@ #define VM_INSERTPAGE 0x02000000 /* The #define VM_ALWAYSDUMP 0x04000000 /* Always include in core dumps */ #define VM_CAN_NONLINEAR 0x08000000 /* Has ->fault & does nonlinear pages */ +#define VM_REVOKED 0x10000000 /* Mapping has been revoked */ #ifndef VM_STACK_DEFAULT_FLAGS /* arch can override this */ #define VM_STACK_DEFAULT_FLAGS VM_DATA_DEFAULT_FLAGS Index: 2.6/mm/memory.c =================================================================== --- 2.6.orig/mm/memory.c 2007-11-23 09:58:11.000000000 +0200 +++ 2.6/mm/memory.c 2007-12-14 16:40:49.000000000 +0200 @@ -2530,6 +2530,9 @@ int handle_mm_fault(struct mm_struct *mm if (unlikely(is_vm_hugetlb_page(vma))) return hugetlb_fault(mm, vma, address, write_access); + if (unlikely(vma->vm_flags & VM_REVOKED)) + return VM_FAULT_SIGBUS; + pgd = pgd_offset(mm, address); pud = pud_alloc(mm, pgd, address); if (!pud) Index: 2.6/mm/mmap.c =================================================================== --- 2.6.orig/mm/mmap.c 2007-12-14 11:33:57.000000000 +0200 +++ 2.6/mm/mmap.c 2007-12-14 16:40:49.000000000 +0200 @@ -1081,10 +1081,14 @@ unsigned long charged = 0; error = -ENOMEM; munmap_back: vma = find_vma_prepare(mm, addr, &prev, &rb_link, &rb_parent); - if (vma && vma->vm_start < addr + len) { - if (do_munmap(mm, addr, len)) - return -ENOMEM; - goto munmap_back; + if (vma) { + if (unlikely(vma->vm_flags & VM_REVOKED)) + return -ENODEV; + if (vma->vm_start < addr + len) { + if (do_munmap(mm, addr, len)) + return -ENOMEM; + goto munmap_back; + } } /* Check against address space limit. */