proc: prevent accessing /proc/<PID>/environ until it's ready

[deliverable/linux.git] / fs / proc / base.c

diff --git a/fs/proc/base.c b/fs/proc/base.c
index b1755b23893e5e34513582d51d7a9cf9ed6b7227..92e37e224cd22d66d0b9675f1790e110d5e7b415 100644 (file)
--- a/fs/proc/base.c
+++ b/fs/proc/base.c
@@ -955,7 +955,8 @@ static ssize_t environ_read(struct file *file, char __user *buf,
        struct mm_struct *mm = file->private_data;
        unsigned long env_start, env_end;
 
-       if (!mm)
+       /* Ensure the process spawned far enough to have an environment. */
+       if (!mm || !mm->env_end)
                return 0;
 
        page = (char *)__get_free_page(GFP_TEMPORARY);