linux-kernel - Re: 2.6.21-rc7-mm2 crash: Eeek! page_mapcount(page) went negative! (-1)

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Date:	Wed, 2 May 2007 00:52:38 -0700
From:	Greg KH <gregkh@...e.de>
To:	Tilman Schmidt <tilman@...p.cc>
Cc:	Kay Sievers <kay.sievers@...y.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	linux-kernel@...r.kernel.org, linux-mm@...ck.org,
	Nick Piggin <nickpiggin@...oo.com.au>,
	Hugh Dickins <hugh@...itas.com>
Subject: Re: 2.6.21-rc7-mm2 crash: Eeek! page_mapcount(page) went negative!
	(-1)

On Wed, May 02, 2007 at 12:10:00AM -0700, Andrew Morton wrote:
> On Wed, 02 May 2007 09:01:22 +0200 Tilman Schmidt <tilman@...p.cc> wrote:
> 
> > Am 30.04.2007 21:46 schrieb Andrew Morton:
> > > Not really - everything's tangled up.  A bisection search on the
> > > 2.6.21-rc7-mm2 driver tree would be the best bet.
> > 
> > And the winner is:
> > 
> > gregkh-driver-driver-core-make-uevent-environment-available-in-uevent-file.patch
> > 
> > Reverting only that from 2.6.21-rc7-mm2 gives me a working kernel
> > again.
> 
> cripes.
> 
> +static ssize_t show_uevent(struct device *dev, struct device_attribute *attr,
> +                          char *buf)
> +{
> +       struct kobject *top_kobj;
> +       struct kset *kset;
> +       char *envp[32];
> +       char data[PAGE_SIZE];
> 
> That won't work too well with 4k stacks.

Tilman, here's a patch, can you try this on top of your tree that dies?

thanks,

greg k-h

---
 drivers/base/core.c |    7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

--- a/drivers/base/core.c
+++ b/drivers/base/core.c
@@ -252,7 +252,7 @@ static ssize_t show_uevent(struct device
 	struct kobject *top_kobj;
 	struct kset *kset;
 	char *envp[32];
-	char data[PAGE_SIZE];
+	char *data = NULL;
 	char *pos;
 	int i;
 	size_t count = 0;
@@ -276,6 +276,10 @@ static ssize_t show_uevent(struct device
 		if (!kset->uevent_ops->filter(kset, &dev->kobj))
 			goto out;
 
+	data = (char *)get_zeroed_page(GFP_KERNEL);
+	if (!data)
+		return -ENOMEM;
+
 	/* let the kset specific function add its keys */
 	pos = data;
 	retval = kset->uevent_ops->uevent(kset, &dev->kobj,
@@ -290,6 +294,7 @@ static ssize_t show_uevent(struct device
 		count += sprintf(pos, "%s\n", envp[i]);
 	}
 out:
+	free_page((unsigned long)data);
 	return count;
 }
 
-
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