From c94c09535c4debcc439f55b5b6d9ebe57bd4665a Mon Sep 17 00:00:00 2001 From: Al Viro Date: Tue, 5 Jul 2016 09:49:21 -0400 Subject: [PATCH] nfs_atomic_open(): prevent parallel nfs_lookup() on a negative hashed Signed-off-by: Al Viro --- fs/nfs/dir.c | 28 +++++++++++++++++++++++++--- 1 file changed, 25 insertions(+), 3 deletions(-) diff --git a/fs/nfs/dir.c b/fs/nfs/dir.c index 3d5eb5edbf50..19d93d0cd400 100644 --- a/fs/nfs/dir.c +++ b/fs/nfs/dir.c @@ -1485,11 +1485,13 @@ int nfs_atomic_open(struct inode *dir, struct dentry *dentry, struct file *file, unsigned open_flags, umode_t mode, int *opened) { + DECLARE_WAIT_QUEUE_HEAD_ONSTACK(wq); struct nfs_open_context *ctx; struct dentry *res; struct iattr attr = { .ia_valid = ATTR_OPEN }; struct inode *inode; unsigned int lookup_flags = 0; + bool switched = false; int err; /* Expect a negative dentry */ @@ -1528,6 +1530,17 @@ int nfs_atomic_open(struct inode *dir, struct dentry *dentry, attr.ia_size = 0; } + if (!(open_flags & O_CREAT) && !d_in_lookup(dentry)) { + d_drop(dentry); + switched = true; + dentry = d_alloc_parallel(dentry->d_parent, + &dentry->d_name, &wq); + if (IS_ERR(dentry)) + return PTR_ERR(dentry); + if (unlikely(!d_in_lookup(dentry))) + return finish_no_open(file, dentry); + } + ctx = create_nfs_open_context(dentry, open_flags); err = PTR_ERR(ctx); if (IS_ERR(ctx)) @@ -1563,14 +1576,23 @@ int nfs_atomic_open(struct inode *dir, struct dentry *dentry, trace_nfs_atomic_open_exit(dir, ctx, open_flags, err); put_nfs_open_context(ctx); out: + if (unlikely(switched)) { + d_lookup_done(dentry); + dput(dentry); + } return err; no_open: res = nfs_lookup(dir, dentry, lookup_flags); - err = PTR_ERR(res); + if (switched) { + d_lookup_done(dentry); + if (!res) + res = dentry; + else + dput(dentry); + } if (IS_ERR(res)) - goto out; - + return PTR_ERR(res); return finish_no_open(file, res); } EXPORT_SYMBOL_GPL(nfs_atomic_open); -- 2.20.1