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From: Al Viro <viro@ZenIV.linux.org.uk>
To: linux-fsdevel@vger.kernel.org
Cc: David Sterba <dsterba@suse.com>, Fabian Frederick <fabf@skynet.be>
Subject: [RFC][PATCH] affs_lookup: switch to d_splice_alias()
Date: Sun, 13 May 2018 17:03:42 +0100	[thread overview]
Message-ID: <20180513160341.GN30522@ZenIV.linux.org.uk> (raw)

Making something exportable takes more than providing ->s_export_ops.
In particular, ->lookup() *MUST* use d_splice_alias() instead of
d_add().

Reading Documentation/filesystems/nfs/Exporting would've been a good idea;
as it is, exporting AFFS is badly (and exploitably) broken.

Partially-Fixes: ed4433d72394 "fs/affs: make affs exportable"
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

diff --git a/fs/affs/namei.c b/fs/affs/namei.c
index 1ed0fa4c4d48..41c5749f4db7 100644
--- a/fs/affs/namei.c
+++ b/fs/affs/namei.c
@@ -201,6 +201,7 @@ affs_lookup(struct inode *dir, struct dentry *dentry, unsigned int flags)
 	struct super_block *sb = dir->i_sb;
 	struct buffer_head *bh;
 	struct inode *inode = NULL;
+	struct dentry *res;
 
 	pr_debug("%s(\"%pd\")\n", __func__, dentry);
 
@@ -223,14 +224,12 @@ affs_lookup(struct inode *dir, struct dentry *dentry, unsigned int flags)
 		}
 		affs_brelse(bh);
 		inode = affs_iget(sb, ino);
-		if (IS_ERR(inode)) {
-			affs_unlock_dir(dir);
-			return ERR_CAST(inode);
-		}
 	}
-	d_add(dentry, inode);
+	res = d_splice_alias(inode, dentry);
+	if (!IS_ERR_OR_NULL(res))
+		res->d_fsdata = dentry->d_fsdata;
 	affs_unlock_dir(dir);
-	return NULL;
+	return res;
 }
 
 int

             reply	other threads:[~2018-05-13 16:03 UTC|newest]

Thread overview: 3+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-05-13 16:03 Al Viro [this message]
2018-05-21 13:46 ` [RFC][PATCH] affs_lookup: switch to d_splice_alias() David Sterba
2018-10-29 16:45 ` Fabian Frederick

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