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From: Miklos Szeredi <miklos@szeredi.hu>
To: Al Viro <viro@zeniv.linux.org.uk>
Cc: linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org,
	linux-unionfs@vger.kernel.org
Subject: [PATCH 2/2] ovl: ignore permissions on underlying lookup
Date: Tue, 22 Mar 2016 14:23:02 +0100	[thread overview]
Message-ID: <20160322132302.GE11906@tucsk> (raw)
In-Reply-To: <20160322132103.GD11906@tucsk>

Generally permission checking is not necessary when overlayfs looks up a
dentry on one of the underlying layers, since search permission on base
directory was already checked in ovl_permission().

More specifically using lookup_one_len() causes a problem when the lower
directory lacks search permission for a specific user while the upper
directory does have search permission.  Since lookups are cached, this
causes inconsistency in behavior: success depends on who did the first
lookup.

So instead use lookup_hash() which doesn't do the permission check.

Reported-by: Ignacy Gawędzki <ignacy.gawedzki@green-communications.fr>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
---
 fs/overlayfs/super.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/fs/overlayfs/super.c
+++ b/fs/overlayfs/super.c
@@ -379,7 +379,7 @@ static inline struct dentry *ovl_lookup_
 	struct dentry *dentry;
 
 	inode_lock(dir->d_inode);
-	dentry = lookup_one_len(name->name, dir, name->len);
+	dentry = lookup_hash(name, dir, 0);
 	inode_unlock(dir->d_inode);
 
 	if (IS_ERR(dentry)) {
--
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WARNING: multiple messages have this Message-ID (diff)
From: Miklos Szeredi <miklos@szeredi.hu>
To: Al Viro <viro@zeniv.linux.org.uk>
Cc: linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org,
	linux-unionfs@vger.kernel.org
Subject: [PATCH 2/2] ovl: ignore permissions on underlying lookup
Date: Tue, 22 Mar 2016 14:23:02 +0100	[thread overview]
Message-ID: <20160322132302.GE11906@tucsk> (raw)
In-Reply-To: <20160322132103.GD11906@tucsk>

Generally permission checking is not necessary when overlayfs looks up a
dentry on one of the underlying layers, since search permission on base
directory was already checked in ovl_permission().

More specifically using lookup_one_len() causes a problem when the lower
directory lacks search permission for a specific user while the upper
directory does have search permission.  Since lookups are cached, this
causes inconsistency in behavior: success depends on who did the first
lookup.

So instead use lookup_hash() which doesn't do the permission check.

Reported-by: Ignacy Gawędzki <ignacy.gawedzki@green-communications.fr>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
---
 fs/overlayfs/super.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/fs/overlayfs/super.c
+++ b/fs/overlayfs/super.c
@@ -379,7 +379,7 @@ static inline struct dentry *ovl_lookup_
 	struct dentry *dentry;
 
 	inode_lock(dir->d_inode);
-	dentry = lookup_one_len(name->name, dir, name->len);
+	dentry = lookup_hash(name, dir, 0);
 	inode_unlock(dir->d_inode);
 
 	if (IS_ERR(dentry)) {

  reply	other threads:[~2016-03-22 13:23 UTC|newest]

Thread overview: 3+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2016-03-22 13:21 [PATCH 1/2] vfs: export lookup_hash() to modules Miklos Szeredi
2016-03-22 13:23 ` Miklos Szeredi [this message]
2016-03-22 13:23   ` [PATCH 2/2] ovl: ignore permissions on underlying lookup Miklos Szeredi

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