1 files changed, 77 insertions, 4 deletions

diff --git a/fs/proc/base.c b/fs/proc/base.c
index 8040f9d1cf07..8fbab527bd24 100644
--- a/fs/proc/base.c
+++ b/fs/proc/base.c
@@ -209,12 +209,53 @@ static int proc_root_link(struct dentry *dentry, struct path *path)
         return result;
 }
 
+/*
+ * If the user used setproctitle(), we just get the string from
+ * user space at arg_start, and limit it to a maximum of one page.
+ */
+static ssize_t get_mm_proctitle(struct mm_struct *mm, char __user *buf,
+                                size_t count, unsigned long pos,
+                                unsigned long arg_start)
+{
+        char *page;
+        int ret, got;
+
+        if (pos >= PAGE_SIZE)
+                return 0;
+
+        page = (char *)__get_free_page(GFP_KERNEL);
+        if (!page)
+                return -ENOMEM;
+
+        ret = 0;
+        got = access_remote_vm(mm, arg_start, page, PAGE_SIZE, FOLL_ANON);
+        if (got > 0) {
+                int len = strnlen(page, got);
+
+                /* Include the NUL character if it was found */
+                if (len < got)
+                        len++;
+
+                if (len > pos) {
+                        len -= pos;
+                        if (len > count)
+                                len = count;
+                        len -= copy_to_user(buf, page+pos, len);
+                        if (!len)
+                                len = -EFAULT;
+                        ret = len;
+                }
+        }
+        free_page((unsigned long)page);
+        return ret;
+}
+
 static ssize_t get_mm_cmdline(struct mm_struct *mm, char __user *buf,
                               size_t count, loff_t *ppos)
 {
-        unsigned long arg_start, arg_end;
+        unsigned long arg_start, arg_end, env_start, env_end;
         unsigned long pos, len;
-        char *page;
+        char *page, c;
 
         /* Check if process spawned far enough to have cmdline. */
         if (!mm->env_end)
@@ -223,14 +264,46 @@ static ssize_t get_mm_cmdline(struct mm_struct *mm, char __user *buf,
         spin_lock(&mm->arg_lock);
         arg_start = mm->arg_start;
         arg_end = mm->arg_end;
+        env_start = mm->env_start;
+        env_end = mm->env_end;
         spin_unlock(&mm->arg_lock);
 
         if (arg_start >= arg_end)
                 return 0;
 
+        /*
+         * We allow setproctitle() to overwrite the argument
+         * strings, and overflow past the original end. But
+         * only when it overflows into the environment area.
+         */
+        if (env_start != arg_end || env_end < env_start)
+                env_start = env_end = arg_end;
+        len = env_end - arg_start;
+
         /* We're not going to care if "*ppos" has high bits set */
-        /* .. but we do check the result is in the proper range */
-        pos = arg_start + *ppos;
+        pos = *ppos;
+        if (pos >= len)
+                return 0;
+        if (count > len - pos)
+                count = len - pos;
+        if (!count)
+                return 0;
+
+        /*
+         * Magical special case: if the argv[] end byte is not
+         * zero, the user has overwritten it with setproctitle(3).
+         *
+         * Possible future enhancement: do this only once when
+         * pos is 0, and set a flag in the 'struct file'.
+         */
+        if (access_remote_vm(mm, arg_end-1, &c, 1, FOLL_ANON) == 1 && c)
+                return get_mm_proctitle(mm, buf, count, pos, arg_start);
+
+        /*
+         * For the non-setproctitle() case we limit things strictly
+         * to the [arg_start, arg_end[ range.
+         */
+        pos += arg_start;
         if (pos < arg_start || pos >= arg_end)
                 return 0;
         if (count > arg_end - pos)