close race in /proc/*/environ

Switch to mm_for_maps().  Maybe we ought to make it r--r--r--,
since we do checks on IO anyway...

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

1 files changed, 4 insertions, 6 deletions

diff --git a/fs/proc/base.c b/fs/proc/base.c
index c28281102082..fc471b8766d1 100644
--- a/fs/proc/base.c
+++ b/fs/proc/base.c
@@ -919,20 +919,18 @@ static ssize_t environ_read(struct file *file, char __user *buf,
         if (!task)
                 goto out_no_task;
 
-        if (!ptrace_may_access(task, PTRACE_MODE_READ))
-                goto out;
-
         ret = -ENOMEM;
         page = (char *)__get_free_page(GFP_TEMPORARY);
         if (!page)
                 goto out;
 
-        ret = 0;
 
-        mm = get_task_mm(task);
-        if (!mm)
+        mm = mm_for_maps(task);
+        ret = PTR_ERR(mm);
+        if (!mm || IS_ERR(mm))
                 goto out_free;
 
+        ret = 0;
         while (count > 0) {
                 int this_len, retval, max_len;