From fe2d35ff0d18a2c93993b0d7d46f846ff4331b72 Mon Sep 17 00:00:00 2001 From: Al Viro Date: Sat, 5 Mar 2011 22:58:25 -0500 Subject: [PATCH] switch non-create side of open() to use of do_last() Instead of path_lookupat() doing trailing symlink resolution, use the same scheme as on the O_CREAT side. Walk with LOOKUP_PARENT, then (in do_last()) look the final component up, then either open it or return error or, if it's a symlink, give the symlink back to path_openat() to be resolved there. The really messy complication here is RCU. We don't want to drop out of RCU mode before the final lookup, since we don't want to bounce parent directory ->d_count without a good reason. Result is _not_ pretty; later in the series we'll clean it up. For now we are roughly back where we'd been before the revert done by Nick's series - top-level logics of path_openat() is cleaned up, do_last() does actual opening, symlink resolution is done uniformly. Signed-off-by: Al Viro --- fs/namei.c | 100 +++++++++++++++++++++++++++++++++++------------------ 1 file changed, 67 insertions(+), 33 deletions(-) diff --git a/fs/namei.c b/fs/namei.c index a260a306daf..9595b4a55c3 100644 --- a/fs/namei.c +++ b/fs/namei.c @@ -2178,13 +2178,14 @@ exit: } /* - * Handle O_CREAT case for do_filp_open + * Handle the last step of open() */ static struct file *do_last(struct nameidata *nd, struct path *path, const struct open_flags *op, const char *pathname) { struct dentry *dir = nd->path.dentry; struct file *filp; + struct inode *inode; int error; nd->flags &= ~LOOKUP_PARENT; @@ -2192,17 +2193,27 @@ static struct file *do_last(struct nameidata *nd, struct path *path, switch (nd->last_type) { case LAST_DOTDOT: - follow_dotdot(nd); - dir = nd->path.dentry; case LAST_DOT: + error = handle_dots(nd, nd->last_type); + if (error) + return ERR_PTR(error); /* fallthrough */ case LAST_ROOT: + if (nd->flags & LOOKUP_RCU) { + if (nameidata_drop_rcu_last(nd)) + return ERR_PTR(-ECHILD); + } error = handle_reval_path(nd); if (error) goto exit; - error = -EISDIR; - goto exit; + audit_inode(pathname, nd->path.dentry); + if (op->open_flag & O_CREAT) { + error = -EISDIR; + goto exit; + } + goto ok; case LAST_BIND: + /* can't be RCU mode here */ error = handle_reval_path(nd); if (error) goto exit; @@ -2210,6 +2221,51 @@ static struct file *do_last(struct nameidata *nd, struct path *path, goto ok; } + if (!(op->open_flag & O_CREAT)) { + if (nd->last.name[nd->last.len]) + nd->flags |= LOOKUP_FOLLOW | LOOKUP_DIRECTORY; + /* we _can_ be in RCU mode here */ + error = do_lookup(nd, &nd->last, path, &inode); + if (error) { + terminate_walk(nd); + return ERR_PTR(error); + } + if (!inode) { + path_to_nameidata(path, nd); + terminate_walk(nd); + return ERR_PTR(-ENOENT); + } + if (unlikely(inode->i_op->follow_link)) { + /* We drop rcu-walk here */ + if (nameidata_dentry_drop_rcu_maybe(nd, path->dentry)) + return ERR_PTR(-ECHILD); + return NULL; + } + path_to_nameidata(path, nd); + nd->inode = inode; + /* sayonara */ + if (nd->flags & LOOKUP_RCU) { + if (nameidata_drop_rcu_last(nd)) + return ERR_PTR(-ECHILD); + } + + error = -ENOTDIR; + if (nd->flags & LOOKUP_DIRECTORY) { + if (!inode->i_op->lookup) + goto exit; + } + audit_inode(pathname, nd->path.dentry); + goto ok; + } + + /* create side of things */ + + if (nd->flags & LOOKUP_RCU) { + if (nameidata_drop_rcu_last(nd)) + return ERR_PTR(-ECHILD); + } + + audit_inode(pathname, dir); error = -EISDIR; /* trailing slashes? */ if (nd->last.name[nd->last.len]) @@ -2303,6 +2359,7 @@ exit: static struct file *path_openat(int dfd, const char *pathname, const struct open_flags *op, int flags) { + struct file *base = NULL; struct file *filp; struct nameidata nd; struct path path; @@ -2318,39 +2375,15 @@ static struct file *path_openat(int dfd, const char *pathname, nd.intent.open.flags = open_to_namei_flags(op->open_flag); nd.intent.open.create_mode = op->mode; - if (op->open_flag & O_CREAT) - goto creat; - - /* !O_CREAT, simple open */ - error = path_lookupat(dfd, pathname, flags | op->intent, &nd); + error = path_init(dfd, pathname, flags | LOOKUP_PARENT, &nd, &base); if (unlikely(error)) goto out_filp; - error = -ELOOP; - if (!(nd.flags & LOOKUP_FOLLOW)) { - if (nd.inode->i_op->follow_link) - goto out_path; - } - error = -ENOTDIR; - if (nd.flags & LOOKUP_DIRECTORY) { - if (!nd.inode->i_op->lookup) - goto out_path; - } - audit_inode(pathname, nd.path.dentry); - filp = finish_open(&nd, op->open_flag, op->acc_mode); - release_open_intent(&nd); - return filp; -creat: - /* OK, have to create the file. Find the parent. */ - error = path_lookupat(dfd, pathname, LOOKUP_PARENT | flags, &nd); + current->total_link_count = 0; + error = link_path_walk(pathname, &nd); if (unlikely(error)) goto out_filp; - if (unlikely(!audit_dummy_context())) - audit_inode(pathname, nd.path.dentry); - /* - * We have the parent and last component. - */ filp = do_last(&nd, &path, op, pathname); while (unlikely(!filp)) { /* trailing symlink */ struct path link = path; @@ -2386,12 +2419,13 @@ creat: out: if (nd.root.mnt) path_put(&nd.root); + if (base) + fput(base); release_open_intent(&nd); return filp; exit_dput: path_put_conditional(&path, &nd); -out_path: path_put(&nd.path); out_filp: filp = ERR_PTR(error); -- 2.41.0