linux-kernel - [PATCH 07/25] dynamic_debug: enlarge command/query write buffer

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Date:	Mon, 25 Jul 2011 15:42:32 -0600
From:	Jim Cromie <jim.cromie@...il.com>
To:	jbaron@...hat.com
Cc:	bvanassche@....org, joe@...ches.com, gregkh@...e.de,
	linux-kernel@...r.kernel.org, gnb@...h.org,
	Jim Cromie <jim.cromie@...il.com>
Subject: [PATCH 07/25] dynamic_debug: enlarge command/query write buffer

Current write buffer is 256 bytes, on stack.  Allocate it off heap,
to fit the size passed by user.   This makes it play nicely with:

 $> cat debug-queries-file > /dbg/dynamic_debug/control

Signed-off-by: Jim Cromie <jim.cromie@...il.com>
---
 lib/dynamic_debug.c |   13 ++++++++-----
 1 files changed, 8 insertions(+), 5 deletions(-)

diff --git a/lib/dynamic_debug.c b/lib/dynamic_debug.c
index 2539517..8ce941a 100644
--- a/lib/dynamic_debug.c
+++ b/lib/dynamic_debug.c
@@ -555,20 +555,23 @@ __setup("ddebug_query=", ddebug_setup_query);
 static ssize_t ddebug_proc_write(struct file *file, const char __user *ubuf,
 				  size_t len, loff_t *offp)
 {
-	char tmpbuf[256];
+	char *tmpbuf;
 	int ret;
 
 	if (len == 0)
 		return 0;
-	/* we don't check *offp -- multiple writes() are allowed */
-	if (len > sizeof(tmpbuf)-1)
-		return -E2BIG;
-	if (copy_from_user(tmpbuf, ubuf, len))
+	tmpbuf = kmalloc(len, GFP_KERNEL);
+	if (!tmpbuf)
+		return -ENOMEM;
+	if (copy_from_user(tmpbuf, ubuf, len)) {
+		kfree(tmpbuf);
 		return -EFAULT;
+	}
 	tmpbuf[len] = '\0';
 	pr_debug("read %d bytes from userspace\n", (int)len);
 
 	ret = ddebug_exec_queries(tmpbuf);
+	kfree(tmpbuf);
 	if (ret)
 		return ret;
 
-- 
1.7.4.1

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