Commit b2c0cea6 authored by J. Bruce Fields's avatar J. Bruce Fields
Browse files

nfsd4: check for negative dentry before use in nfsv4 readdir 



After 2f9092e1 "Fix i_mutex vs.  readdir
handling in nfsd" (and 14f7dd63 "Copy XFS readdir hack into nfsd code"),
an entry may be removed between the first mutex_unlock and the second
mutex_lock. In this case, lookup_one_len() will return a negative
dentry.  Check for this case to avoid a NULL dereference.

Signed-off-by: default avatarJ. Bruce Fields <bfields@citi.umich.edu>
Reviewed-by: default avatarJ. R. Okajima <hooanon05@yahoo.co.jp>
Cc: stable@kernel.org
parent ccecee1e

fs/nfsd/nfs4xdr.c

+15 −1
Original line number Diff line number Diff line
@@ -2214,6 +2214,15 @@ nfsd4_encode_dirent_fattr(struct nfsd4_readdir *cd, 
	dentry = lookup_one_len(name, cd->rd_fhp->fh_dentry, namlen);

	if (IS_ERR(dentry))

		return nfserrno(PTR_ERR(dentry));

	if (!dentry->d_inode) {

		/*

		 * nfsd_buffered_readdir drops the i_mutex between

		 * readdir and calling this callback, leaving a window

		 * where this directory entry could have gone away.

		 */

		dput(dentry);

		return nfserr_noent;

	}



	exp_get(exp);

	/*
@@ -2276,6 +2285,7 @@ nfsd4_encode_dirent(void *ccdv, const char *name, int namlen, 
	struct nfsd4_readdir *cd = container_of(ccd, struct nfsd4_readdir, common);

	int buflen;

	__be32 *p = cd->buffer;

	__be32 *cookiep;

	__be32 nfserr = nfserr_toosmall;



	/* In nfsv4, "." and ".." never make it onto the wire.. */
@@ -2292,7 +2302,7 @@ nfsd4_encode_dirent(void *ccdv, const char *name, int namlen, 
		goto fail;



	*p++ = xdr_one;                             /* mark entry present */

	cd->offset = p;                             /* remember pointer */

	cookiep = p;

	p = xdr_encode_hyper(p, NFS_OFFSET_MAX);    /* offset of next entry */

	p = xdr_encode_array(p, name, namlen);      /* name length & name */
@@ -2306,6 +2316,8 @@ nfsd4_encode_dirent(void *ccdv, const char *name, int namlen, 
		goto fail;

	case nfserr_dropit:

		goto fail;

	case nfserr_noent:

		goto skip_entry;

	default:

		/*

		 * If the client requested the RDATTR_ERROR attribute,
@@ -2324,6 +2336,8 @@ nfsd4_encode_dirent(void *ccdv, const char *name, int namlen, 
	}

	cd->buflen -= (p - cd->buffer);

	cd->buffer = p;

	cd->offset = cookiep;

skip_entry:

	cd->common.err = nfs_ok;

	return 0;

fail:

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