[PATCH] NOMMU: Check that access_process_vm() has a valid target

Check that access_process_vm() is accessing a valid mapping in the target
process.

This limits ptrace() accesses and accesses through /proc/<pid>/maps to only
those regions actually mapped by a program.

Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

diff --git a/kernel/ptrace.c b/kernel/ptrace.c
index 9a111f7..8aad033 100644 (file)
--- a/kernel/ptrace.c
+++ b/kernel/ptrace.c
@@ -241,60 +241,6 @@ int ptrace_detach(struct task_struct *child, unsigned int data)
        return 0;
 }
 
-/*
- * Access another process' address space.
- * Source/target buffer must be kernel space, 
- * Do not walk the page table directly, use get_user_pages
- */
-
-int access_process_vm(struct task_struct *tsk, unsigned long addr, void *buf, int len, int write)
-{
-       struct mm_struct *mm;
-       struct vm_area_struct *vma;
-       struct page *page;
-       void *old_buf = buf;
-
-       mm = get_task_mm(tsk);
-       if (!mm)
-               return 0;
-
-       down_read(&mm->mmap_sem);
-       /* ignore errors, just check how much was sucessfully transfered */
-       while (len) {
-               int bytes, ret, offset;
-               void *maddr;
-
-               ret = get_user_pages(tsk, mm, addr, 1,
-                               write, 1, &page, &vma);
-               if (ret <= 0)
-                       break;
-
-               bytes = len;
-               offset = addr & (PAGE_SIZE-1);
-               if (bytes > PAGE_SIZE-offset)
-                       bytes = PAGE_SIZE-offset;
-
-               maddr = kmap(page);
-               if (write) {
-                       copy_to_user_page(vma, page, addr,
-                                         maddr + offset, buf, bytes);
-                       set_page_dirty_lock(page);
-               } else {
-                       copy_from_user_page(vma, page, addr,
-                                           buf, maddr + offset, bytes);
-               }
-               kunmap(page);
-               page_cache_release(page);
-               len -= bytes;
-               buf += bytes;
-               addr += bytes;
-       }
-       up_read(&mm->mmap_sem);
-       mmput(mm);
-       
-       return buf - old_buf;
-}
-
 int ptrace_readdata(struct task_struct *tsk, unsigned long src, char __user *dst, int len)
 {
        int copied = 0;

diff --git a/mm/memory.c b/mm/memory.c
index f2ef1dc..601159a 100644 (file)
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -2604,3 +2604,56 @@ int in_gate_area_no_task(unsigned long addr)
 }
 
 #endif /* __HAVE_ARCH_GATE_AREA */
+
+/*
+ * Access another process' address space.
+ * Source/target buffer must be kernel space,
+ * Do not walk the page table directly, use get_user_pages
+ */
+int access_process_vm(struct task_struct *tsk, unsigned long addr, void *buf, int len, int write)
+{
+       struct mm_struct *mm;
+       struct vm_area_struct *vma;
+       struct page *page;
+       void *old_buf = buf;
+
+       mm = get_task_mm(tsk);
+       if (!mm)
+               return 0;
+
+       down_read(&mm->mmap_sem);
+       /* ignore errors, just check how much was sucessfully transfered */
+       while (len) {
+               int bytes, ret, offset;
+               void *maddr;
+
+               ret = get_user_pages(tsk, mm, addr, 1,
+                               write, 1, &page, &vma);
+               if (ret <= 0)
+                       break;
+
+               bytes = len;
+               offset = addr & (PAGE_SIZE-1);
+               if (bytes > PAGE_SIZE-offset)
+                       bytes = PAGE_SIZE-offset;
+
+               maddr = kmap(page);
+               if (write) {
+                       copy_to_user_page(vma, page, addr,
+                                         maddr + offset, buf, bytes);
+                       set_page_dirty_lock(page);
+               } else {
+                       copy_from_user_page(vma, page, addr,
+                                           buf, maddr + offset, bytes);
+               }
+               kunmap(page);
+               page_cache_release(page);
+               len -= bytes;
+               buf += bytes;
+               addr += bytes;
+       }
+       up_read(&mm->mmap_sem);
+       mmput(mm);
+
+       return buf - old_buf;
+}

diff --git a/mm/nommu.c b/mm/nommu.c
index d99dea3..d08acda 100644 (file)
--- a/mm/nommu.c
+++ b/mm/nommu.c
@@ -1206,3 +1206,50 @@ struct page *filemap_nopage(struct vm_area_struct *area,
        BUG();
        return NULL;
 }
+
+/*
+ * Access another process' address space.
+ * - source/target buffer must be kernel space
+ */
+int access_process_vm(struct task_struct *tsk, unsigned long addr, void *buf, int len, int write)
+{
+       struct vm_list_struct *vml;
+       struct vm_area_struct *vma;
+       struct mm_struct *mm;
+
+       if (addr + len < addr)
+               return 0;
+
+       mm = get_task_mm(tsk);
+       if (!mm)
+               return 0;
+
+       down_read(&mm->mmap_sem);
+
+       /* the access must start within one of the target process's mappings */
+       for (vml = mm->context.vmlist; vml; vml = vml->next)
+               if (addr >= vml->vma->vm_start && addr < vml->vma->vm_end)
+                       break;
+
+       if (vml) {
+               vma = vml->vma;
+
+               /* don't overrun this mapping */
+               if (addr + len >= vma->vm_end)
+                       len = vma->vm_end - addr;
+
+               /* only read or write mappings where it is permitted */
+               if (write && vma->vm_flags & VM_WRITE)
+                       len -= copy_to_user((void *) addr, buf, len);
+               else if (!write && vma->vm_flags & VM_READ)
+                       len -= copy_from_user(buf, (void *) addr, len);
+               else
+                       len = 0;
+       } else {
+               len = 0;
+       }
+
+       up_read(&mm->mmap_sem);
+       mmput(mm);
+       return len;
+}