linux-kernel - [PATCH] module: clean up initialization of variable

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Date:	Mon, 5 Jan 2009 15:30:25 -0500 (EST)
From:	Steven Rostedt <rostedt@...dmis.org>
To:	Sam Ravnborg <sam@...nborg.org>
cc:	LKML <linux-kernel@...r.kernel.org>,
	Steven Rostedt <srostedt@...hat.com>,
	Ingo Molnar <mingo@...e.hu>,
	"David S. Miller" <davem@...emloft.net>,
	sparclinux <sparclinux@...r.kernel.org>,
	Rusty Russell <rusty@...tcorp.com.au>,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: [PATCH] module: clean up initialization of variable



Impact: clean up

On Mon, 5 Jan 2009, Sam Ravnborg wrote:
> 
> Fully ageed on the readability.
> I happen to trigger this as an error in the sparc code.
> But I see the same warning also in generic code.
> 
> >From kernel/module.c:
>         /* Suck in entire file: we'll want most of it. */
>         /* vmalloc barfs on "unusual" numbers.  Check here */
>         if (len > 64 * 1024 * 1024 || (hdr = vmalloc(len)) == NULL)
>                 return ERR_PTR(-ENOMEM);
> 
> 
> This gives following warning:
> kernel/module.c: In function `load_module':
> kernel/module.c:1842: warning: 'hdr' might be used uninitialized in this function

The above is caused by having the branch tracer on and the following type 
of initialization:

	if (x || !(y = init_me())
		return;

	use_me(y);

This is sloppy initialization because it initializes, not only in an
if condition, but also as the second part of a complex conditional.

This patch makes the code a bit easier to read.

Signed-off-by: Steven Rostedt <srostedt@...hat.com>
Reported-by: Sam Ravnborg <sam@...nborg.org>

diff --git a/kernel/module.c b/kernel/module.c
index 9712c52..112d6cd 100644
--- a/kernel/module.c
+++ b/kernel/module.c
@@ -1864,7 +1864,10 @@ static noinline struct module *load_module(void __user *umod,
 
 	/* Suck in entire file: we'll want most of it. */
 	/* vmalloc barfs on "unusual" numbers.  Check here */
-	if (len > 64 * 1024 * 1024 || (hdr = vmalloc(len)) == NULL)
+	if (len > 64 * 1024 * 1024)
+		return ERR_PTR(-ENOMEM);
+	hdr = vmalloc(len);
+	if (hdr == NULL)
 		return ERR_PTR(-ENOMEM);
 	if (copy_from_user(hdr, umod, len) != 0) {
 		err = -EFAULT;
--
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