1 files changed, 105 insertions, 9 deletions

diff --git a/fs/proc/base.c b/fs/proc/base.c
index c5e412a00b17..808cbdc193d3 100644
--- a/fs/proc/base.c
+++ b/fs/proc/base.c
@@ -56,6 +56,7 @@
 #include <linux/init.h>
 #include <linux/capability.h>
 #include <linux/file.h>
+#include <linux/fdtable.h>
 #include <linux/string.h>
 #include <linux/seq_file.h>
 #include <linux/namei.h>
@@ -195,12 +196,32 @@ static int proc_root_link(struct inode *inode, struct path *path)
         return result;
 }
 
-#define MAY_PTRACE(task) \
-        (task == current || \
-        (task->parent == current && \
-        (task->ptrace & PT_PTRACED) && \
-         (task_is_stopped_or_traced(task)) && \
-         security_ptrace(current,task) == 0))
+/*
+ * Return zero if current may access user memory in @task, -error if not.
+ */
+static int check_mem_permission(struct task_struct *task)
+{
+        /*
+         * A task can always look at itself, in case it chooses
+         * to use system calls instead of load instructions.
+         */
+        if (task == current)
+                return 0;
+
+        /*
+         * If current is actively ptrace'ing, and would also be
+         * permitted to freshly attach with ptrace now, permit it.
+         */
+        if (task->parent == current && (task->ptrace & PT_PTRACED) &&
+            task_is_stopped_or_traced(task) &&
+            ptrace_may_attach(task))
+                return 0;
+
+        /*
+         * Noone else is allowed.
+         */
+        return -EPERM;
+}
 
 struct mm_struct *mm_for_maps(struct task_struct *task)
 {
@@ -722,7 +743,7 @@ static ssize_t mem_read(struct file * file, char __user * buf,
         if (!task)
                 goto out_no_task;
 
-        if (!MAY_PTRACE(task) || !ptrace_may_attach(task))
+        if (check_mem_permission(task))
                 goto out;
 
         ret = -ENOMEM;
@@ -748,7 +769,7 @@ static ssize_t mem_read(struct file * file, char __user * buf,
 
                 this_len = (count > PAGE_SIZE) ? PAGE_SIZE : count;
                 retval = access_process_vm(task, src, page, this_len, 0);
-                if (!retval || !MAY_PTRACE(task) || !ptrace_may_attach(task)) {
+                if (!retval || check_mem_permission(task)) {
                         if (!ret)
                                 ret = -EIO;
                         break;
@@ -792,7 +813,7 @@ static ssize_t mem_write(struct file * file, const char __user *buf,
         if (!task)
                 goto out_no_task;
 
-        if (!MAY_PTRACE(task) || !ptrace_may_attach(task))
+        if (check_mem_permission(task))
                 goto out;
 
         copied = -ENOMEM;
@@ -1181,6 +1202,81 @@ static const struct file_operations proc_pid_sched_operations = {
 
 #endif
 
+/*
+ * We added or removed a vma mapping the executable. The vmas are only mapped
+ * during exec and are not mapped with the mmap system call.
+ * Callers must hold down_write() on the mm's mmap_sem for these
+ */
+void added_exe_file_vma(struct mm_struct *mm)
+{
+        mm->num_exe_file_vmas++;
+}
+
+void removed_exe_file_vma(struct mm_struct *mm)
+{
+        mm->num_exe_file_vmas--;
+        if ((mm->num_exe_file_vmas == 0) && mm->exe_file){
+                fput(mm->exe_file);
+                mm->exe_file = NULL;
+        }
+
+}
+
+void set_mm_exe_file(struct mm_struct *mm, struct file *new_exe_file)
+{
+        if (new_exe_file)
+                get_file(new_exe_file);
+        if (mm->exe_file)
+                fput(mm->exe_file);
+        mm->exe_file = new_exe_file;
+        mm->num_exe_file_vmas = 0;
+}
+
+struct file *get_mm_exe_file(struct mm_struct *mm)
+{
+        struct file *exe_file;
+
+        /* We need mmap_sem to protect against races with removal of
+         * VM_EXECUTABLE vmas */
+        down_read(&mm->mmap_sem);
+        exe_file = mm->exe_file;
+        if (exe_file)
+                get_file(exe_file);
+        up_read(&mm->mmap_sem);
+        return exe_file;
+}
+
+void dup_mm_exe_file(struct mm_struct *oldmm, struct mm_struct *newmm)
+{
+        /* It's safe to write the exe_file pointer without exe_file_lock because
+         * this is called during fork when the task is not yet in /proc */
+        newmm->exe_file = get_mm_exe_file(oldmm);
+}
+
+static int proc_exe_link(struct inode *inode, struct path *exe_path)
+{
+        struct task_struct *task;
+        struct mm_struct *mm;
+        struct file *exe_file;
+
+        task = get_proc_task(inode);
+        if (!task)
+                return -ENOENT;
+        mm = get_task_mm(task);
+        put_task_struct(task);
+        if (!mm)
+                return -ENOENT;
+        exe_file = get_mm_exe_file(mm);
+        mmput(mm);
+        if (exe_file) {
+                *exe_path = exe_file->f_path;
+                path_get(&exe_file->f_path);
+                fput(exe_file);
+                return 0;
+        } else
+                return -ENOENT;
+}
+
 static void *proc_pid_follow_link(struct dentry *dentry, struct nameidata *nd)
 {
         struct inode *inode = dentry->d_inode;