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-rw-r--r--fs/namei.c45
1 files changed, 45 insertions, 0 deletions
diff --git a/fs/namei.c b/fs/namei.c
index a765e7a741f4..d2783c8a770b 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -414,6 +414,46 @@ do_revalidate(struct dentry *dentry, struct nameidata *nd)
}
/*
+ * force_reval_path - force revalidation of a dentry
+ *
+ * In some situations the path walking code will trust dentries without
+ * revalidating them. This causes problems for filesystems that depend on
+ * d_revalidate to handle file opens (e.g. NFSv4). When FS_REVAL_DOT is set
+ * (which indicates that it's possible for the dentry to go stale), force
+ * a d_revalidate call before proceeding.
+ *
+ * Returns 0 if the revalidation was successful. If the revalidation fails,
+ * either return the error returned by d_revalidate or -ESTALE if the
+ * revalidation it just returned 0. If d_revalidate returns 0, we attempt to
+ * invalidate the dentry. It's up to the caller to handle putting references
+ * to the path if necessary.
+ */
+static int
+force_reval_path(struct path *path, struct nameidata *nd)
+{
+ int status;
+ struct dentry *dentry = path->dentry;
+
+ /*
+ * only check on filesystems where it's possible for the dentry to
+ * become stale. It's assumed that if this flag is set then the
+ * d_revalidate op will also be defined.
+ */
+ if (!(dentry->d_sb->s_type->fs_flags & FS_REVAL_DOT))
+ return 0;
+
+ status = dentry->d_op->d_revalidate(dentry, nd);
+ if (status > 0)
+ return 0;
+
+ if (!status) {
+ d_invalidate(dentry);
+ status = -ESTALE;
+ }
+ return status;
+}
+
+/*
* Short-cut version of permission(), for calling on directories
* during pathname resolution. Combines parts of permission()
* and generic_permission(), and tests ONLY for MAY_EXEC permission.
@@ -529,6 +569,11 @@ static __always_inline int __do_follow_link(struct path *path, struct nameidata
error = 0;
if (s)
error = __vfs_follow_link(nd, s);
+ else if (nd->last_type == LAST_BIND) {
+ error = force_reval_path(&nd->path, nd);
+ if (error)
+ path_put(&nd->path);
+ }
if (dentry->d_inode->i_op->put_link)
dentry->d_inode->i_op->put_link(dentry, nd, cookie);
}