From ed0321895182ffb6ecf210e066d87911b270d587 Mon Sep 17 00:00:00 2001 From: Eric Paris Date: Thu, 28 Jun 2007 15:55:21 -0400 Subject: security: Protection for exploiting null dereference using mmap Add a new security check on mmap operations to see if the user is attempting to mmap to low area of the address space. The amount of space protected is indicated by the new proc tunable /proc/sys/vm/mmap_min_addr and defaults to 0, preserving existing behavior. This patch uses a new SELinux security class "memprotect." Policy already contains a number of allow rules like a_t self:process * (unconfined_t being one of them) which mean that putting this check in the process class (its best current fit) would make it useless as all user processes, which we also want to protect against, would be allowed. By taking the memprotect name of the new class it will also make it possible for us to move some of the other memory protect permissions out of 'process' and into the new class next time we bump the policy version number (which I also think is a good future idea) Acked-by: Stephen Smalley Acked-by: Chris Wright Signed-off-by: Eric Paris Signed-off-by: James Morris --- mm/mremap.c | 13 +++++++++++-- 1 file changed, 11 insertions(+), 2 deletions(-) (limited to 'mm/mremap.c') diff --git a/mm/mremap.c b/mm/mremap.c index 5d4bd4f95b8..bc7c52efc71 100644 --- a/mm/mremap.c +++ b/mm/mremap.c @@ -291,6 +291,10 @@ unsigned long do_mremap(unsigned long addr, if ((addr <= new_addr) && (addr+old_len) > new_addr) goto out; + ret = security_file_mmap(0, 0, 0, 0, new_addr, 1); + if (ret) + goto out; + ret = do_munmap(mm, new_addr, new_len); if (ret) goto out; @@ -390,8 +394,13 @@ unsigned long do_mremap(unsigned long addr, new_addr = get_unmapped_area(vma->vm_file, 0, new_len, vma->vm_pgoff, map_flags); - ret = new_addr; - if (new_addr & ~PAGE_MASK) + if (new_addr & ~PAGE_MASK) { + ret = new_addr; + goto out; + } + + ret = security_file_mmap(0, 0, 0, 0, new_addr, 1); + if (ret) goto out; } ret = move_vma(vma, addr, old_len, new_len, new_addr); -- cgit v1.2.3