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Message-Id: <20060829175951.32281.76850.stgit@warthog.cambridge.redhat.com>
Date: Tue, 29 Aug 2006 18:59:51 +0100
From: David Howells <dhowells@...hat.com>
To: torvalds@...l.org, akpm@...l.org
Cc: linux-kernel@...r.kernel.org, uclinux-dev@...inux.org,
dhowells@...hat.com
Subject: [PATCH 2/2] NOMMU: Check that access_process_vm() has a valid target
From: David Howells <dhowells@...hat.com>
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@...hat.com>
---
kernel/ptrace.c | 54 ------------------------------------------------------
mm/memory.c | 53 +++++++++++++++++++++++++++++++++++++++++++++++++++++
mm/nommu.c | 47 +++++++++++++++++++++++++++++++++++++++++++++++
3 files changed, 100 insertions(+), 54 deletions(-)
diff --git a/kernel/ptrace.c b/kernel/ptrace.c
index 9a111f7..8aad033 100644
--- a/kernel/ptrace.c
+++ b/kernel/ptrace.c
@@ -241,60 +241,6 @@ int ptrace_detach(struct task_struct *ch
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 109e986..f915984 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -2505,3 +2505,56 @@ #endif
}
#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 c576df7..663ec1c 100644
--- a/mm/nommu.c
+++ b/mm/nommu.c
@@ -1206,3 +1206,50 @@ struct page *filemap_nopage(struct vm_ar
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;
+}
-
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