From 3819bb0d79f50b05910db5bdc6d9ef512184e3b1 Mon Sep 17 00:00:00 2001 From: Al Viro Date: Fri, 11 May 2018 17:03:19 -0400 Subject: [PATCH] nfsd: vfs_mkdir() might succeed leaving dentry negative unhashed That can (and does, on some filesystems) happen - ->mkdir() (and thus vfs_mkdir()) can legitimately leave its argument negative and just unhash it, counting upon the lookup to pick the object we'd created next time we try to look at that name. Some vfs_mkdir() callers forget about that possibility... Acked-by: J. Bruce Fields Signed-off-by: Al Viro --- fs/nfsd/vfs.c | 22 ++++++++++++++++++++++ 1 file changed, 22 insertions(+) diff --git a/fs/nfsd/vfs.c b/fs/nfsd/vfs.c index 2410b09..b0555d7 100644 --- a/fs/nfsd/vfs.c +++ b/fs/nfsd/vfs.c @@ -1201,6 +1201,28 @@ nfsd_create_locked(struct svc_rqst *rqstp, struct svc_fh *fhp, break; case S_IFDIR: host_err = vfs_mkdir(dirp, dchild, iap->ia_mode); + if (!host_err && unlikely(d_unhashed(dchild))) { + struct dentry *d; + d = lookup_one_len(dchild->d_name.name, + dchild->d_parent, + dchild->d_name.len); + if (IS_ERR(d)) { + host_err = PTR_ERR(d); + break; + } + if (unlikely(d_is_negative(d))) { + dput(d); + err = nfserr_serverfault; + goto out; + } + dput(resfhp->fh_dentry); + resfhp->fh_dentry = dget(d); + err = fh_update(resfhp); + dput(dchild); + dchild = d; + if (err) + goto out; + } break; case S_IFCHR: case S_IFBLK: -- 2.7.4