From: Hiroshi Shimamoto <h-shimamoto@ct.jp.nec.com>
Date: Thu, 14 Feb 2008 18:26:24 +0000 (-0800)
Subject: latencytop: fix kernel panic while reading latency proc file
X-Git-Tag: v2.6.25-rc4~160^2~2
X-Git-Url: https://err.no/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=ae0027869db7d28563cd783865fab04ffd18419c;p=linux-2.6

latencytop: fix kernel panic while reading latency proc file

Reading /proc/<pid>/latency or /proc/<pid>/task/<tid>/latency could cause
NULL pointer dereference.

In lstats_open(), get_proc_task() can return NULL, in which case the kernel
will oops at lstats_show_proc() because m->private is NULL.

When get_proc_task() returns NULL, the kernel should return -ENOENT.

This can be reproduced by the following script.
while :
do
        date
        bash -c 'ls > ls.$$' &
        pid=$!
        cat /proc/$pid/latency &
        cat /proc/$pid/latency &
        cat /proc/$pid/latency &
        cat /proc/$pid/latency
done

Signed-off-by: Hiroshi Shimamoto <h-shimamoto@ct.jp.nec.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
---

diff --git a/fs/proc/base.c b/fs/proc/base.c
index 96ee899d65..989e3078d7 100644
--- a/fs/proc/base.c
+++ b/fs/proc/base.c
@@ -350,6 +350,8 @@ static int lstats_open(struct inode *inode, struct file *file)
 	struct seq_file *m;
 	struct task_struct *task = get_proc_task(inode);
 
+	if (!task)
+		return -ENOENT;
 	ret = single_open(file, lstats_show_proc, NULL);
 	if (!ret) {
 		m = file->private_data;