linux-kernel - [PATCH] lost content of /proc/sys/fs/binfmt

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Date:	Wed, 5 Dec 2007 17:35:18 +0300
From:	"Denis V. Lunev" <den@...nvz.org>
To:	akpm@...ux-foundation.org
Cc:	ebiederm@...ssion.com, marcus@...ter.se, containers@...ts.osdl.org,
	devel@...nvz.org, linux-kernel@...r.kernel.org, den@...nvz.org
Subject: [PATCH] lost content of /proc/sys/fs/binfmt_misc

/proc/sys/fs/binfmt_misc dentry disappeared during d_revalidate.
d_revalidate only dentries from shadowed one and below.
http://bugzilla.kernel.org/show_bug.cgi?id=9504

CC: Eric W. Biederman <ebiederm@...ssion.com>
CC: Marcus Better <marcus@...ter.se>
Signed-off-by: Denis V. Lunev <den@...nvz.org>

diff --git a/fs/proc/generic.c b/fs/proc/generic.c
index 5fccfe2..1497ac4 100644
--- a/fs/proc/generic.c
+++ b/fs/proc/generic.c
@@ -380,12 +380,17 @@ static int proc_revalidate_dentry(struct dentry *dentry, struct nameidata *nd)
 	return 0;
 }
 
-static struct dentry_operations proc_dentry_operations =
+static struct dentry_operations proc_dentry_shadow_operations =
 {
 	.d_delete	= proc_delete_dentry,
 	.d_revalidate	= proc_revalidate_dentry,
 };
 
+static struct dentry_operations proc_dentry_operations =
+{
+	.d_delete	= proc_delete_dentry,
+};
+
 /*
  * Don't create negative dentries here, return -ENOENT by hand
  * instead.
@@ -394,6 +399,7 @@ struct dentry *proc_lookup(struct inode * dir, struct dentry *dentry, struct nam
 {
 	struct inode *inode = NULL;
 	struct proc_dir_entry * de;
+	int use_shadow = 0;
 	int error = -ENOENT;
 
 	lock_kernel();
@@ -406,8 +412,10 @@ struct dentry *proc_lookup(struct inode * dir, struct dentry *dentry, struct nam
 			if (!memcmp(dentry->d_name.name, de->name, de->namelen)) {
 				unsigned int ino;
 
-				if (de->shadow_proc)
+				if (de->shadow_proc) {
 					de = de->shadow_proc(current, de);
+					use_shadow = 1;
+				}
 				ino = de->low_ino;
 				de_get(de);
 				spin_unlock(&proc_subdir_lock);
@@ -423,6 +431,8 @@ struct dentry *proc_lookup(struct inode * dir, struct dentry *dentry, struct nam
 
 	if (inode) {
 		dentry->d_op = &proc_dentry_operations;
+		dentry->d_op = use_shadow ?
+			&proc_dentry_shadow_operations : dentry->d_parent->d_op;
 		d_add(dentry, inode);
 		return NULL;
 	}
--
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