Commit f39c0104 authored Sep 11, 2014 by NeilBrown Committed by Trond Myklebust Sep 12, 2014

NFS: remove BUG possibility in nfs4_open_and_get_state



commit 4fa2c54b
    NFS: nfs4_do_open should add negative results to the dcache.

used "d_drop(); d_add();" to ensure that a dentry was hashed
as a negative cached entry.
This is not safe if the dentry has an non-NULL ->d_inode.
It will trigger a BUG_ON in d_instantiate().
In that case, d_delete() is needed.

Also, only d_add if the dentry is currently unhashed, it seems
pointless removed and re-adding it unchanged.

Reported-by: Christoph Hellwig <hch@infradead.org>
Fixes: 4fa2c54b
Cc: Jeff Layton <jeff.layton@primarydata.com>
Link: http://lkml.kernel.org/r/20140908144525.GB19811@infradead.org


Signed-off-by: NeilBrown <neilb@suse.de>
Acked-by: Jeff Layton <jlayton@primarydata.com>
Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>

parent 224ecbf5

fs/nfs/nfs4proc.c

+7 −3

Original line number	Diff line number	Diff line
		@@ -2226,9 +2226,13 @@ static int _nfs4_open_and_get_state(struct nfs4_opendata *opendata,
		ret = _nfs4_proc_open(opendata);
		if (ret != 0) {
		if (ret == -ENOENT) {
		d_drop(opendata->dentry);
		d_add(opendata->dentry, NULL);
		nfs_set_verifier(opendata->dentry,
		dentry = opendata->dentry;
		if (dentry->d_inode)
		d_delete(dentry);
		else if (d_unhashed(dentry))
		d_add(dentry, NULL);

		nfs_set_verifier(dentry,
		nfs_save_change_attribute(opendata->dir->d_inode));
		}
		goto out;

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