Re: [ANNOUNCE] 2.6.33-rc8-rt1

[Carsten Emde]

On 02/22/2010 02:29 PM, Dan Carpenter wrote:
> kernel/trace/latency_hist.c
>    373  static ssize_t
>    374  latency_hist_show_maxlatproc(struct file *filp, char __user *ubuf,
>    375                        size_t cnt, loff_t *ppos)
>    376  {
>    377          char buf[1024];
> 
> This is a large buffer to put on the stack.
Thanks!

Remove stack allocation of buffer space, use dyn memory instead.
Use a better assumption to estimate the required buffer space.

Signed-off-by: Carsten Emde <C.Emde@xxxxxxxxx>

Subject: histogram-maxlatproc-use-dyn-mem.patch
From: Carsten Emde <C.Emde@xxxxxxxxx>
Date: Wed, 24 Feb 2010 07:49:33 +0100

Remove stack allocation of buffer space, use dyn memory instead.
Use a better assumption to estimate the required buffer space. 

Reported-by: Dan Carpenter <error27@xxxxxxxxx>
Signed-off-by: Carsten Emde <C.Emde@xxxxxxxxx>

Index: head/kernel/trace/latency_hist.c
===================================================================
--- head.orig/kernel/trace/latency_hist.c
+++ head/kernel/trace/latency_hist.c
@@ -442,13 +442,19 @@ static ssize_t do_pid(struct file *file,
 static ssize_t
 show_maxlatproc(struct file *file, char __user *ubuf, size_t cnt, loff_t *ppos)
 {
-	char buf[1024];
 	int r;
 	struct maxlatproc_data *mp = file->private_data;
+	int strmaxlen = TASK_COMM_LEN + 32;
+	char *buf = kmalloc(strmaxlen, GFP_KERNEL);
 
-	r = snprintf(buf, sizeof(buf), "%d %d %ld %s\n",
+	if (buf == NULL)
+		return -ENOMEM;
+
+	r = snprintf(buf, strmaxlen, "%d %d %ld %s\n",
 	    mp->pid, MAX_RT_PRIO-1 - mp->prio, mp->latency, mp->comm);
-	return simple_read_from_buffer(ubuf, cnt, ppos, buf, r);
+	r = simple_read_from_buffer(ubuf, cnt, ppos, buf, r);
+	kfree(buf);
+	return r;
 }
 #endif