From 5d38f049cee1e1c4a7ac55aa79d37d01ddcc3860 Mon Sep 17 00:00:00 2001 From: Ian Kent Date: Wed, 29 Nov 2017 16:11:26 -0800 Subject: [PATCH] autofs: revert "autofs: fix AT_NO_AUTOMOUNT not being honored" Commit 42f461482178 ("autofs: fix AT_NO_AUTOMOUNT not being honored") allowed the fstatat(2) system call to properly honor the AT_NO_AUTOMOUNT flag but introduced a semantic change. In order to honor AT_NO_AUTOMOUNT a semantic change was made to the negative dentry case for stat family system calls in follow_automount(). This changed the unconditional triggering of an automount in this case to no longer be done and an error returned instead. This has caused more problems than I expected so reverting the change is needed. In a discussion with Neil Brown it was concluded that the automount(8) daemon can implement this change without kernel modifications. So that will be done instead and the autofs module documentation updated with a description of the problem and what needs to be done by module users for this specific case. Link: http://lkml.kernel.org/r/151174730120.6162.3848002191530283984.stgit@pluto.themaw.net Fixes: 42f4614821 ("autofs: fix AT_NO_AUTOMOUNT not being honored") Signed-off-by: Ian Kent Cc: Neil Brown Cc: Al Viro Cc: David Howells Cc: Colin Walters Cc: Ondrej Holy Cc: [4.11+] Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- fs/namei.c | 15 +++------------ include/linux/fs.h | 3 ++- 2 files changed, 5 insertions(+), 13 deletions(-) diff --git a/fs/namei.c b/fs/namei.c index f0c7a7b9b6ca..9cc91fb7f156 100644 --- a/fs/namei.c +++ b/fs/namei.c @@ -1129,18 +1129,9 @@ static int follow_automount(struct path *path, struct nameidata *nd, * of the daemon to instantiate them before they can be used. */ if (!(nd->flags & (LOOKUP_PARENT | LOOKUP_DIRECTORY | - LOOKUP_OPEN | LOOKUP_CREATE | - LOOKUP_AUTOMOUNT))) { - /* Positive dentry that isn't meant to trigger an - * automount, EISDIR will allow it to be used, - * otherwise there's no mount here "now" so return - * ENOENT. - */ - if (path->dentry->d_inode) - return -EISDIR; - else - return -ENOENT; - } + LOOKUP_OPEN | LOOKUP_CREATE | LOOKUP_AUTOMOUNT)) && + path->dentry->d_inode) + return -EISDIR; if (path->dentry->d_sb->s_user_ns != &init_user_ns) return -EACCES; diff --git a/include/linux/fs.h b/include/linux/fs.h index 9dc498d16cc1..511fbaabf624 100644 --- a/include/linux/fs.h +++ b/include/linux/fs.h @@ -3088,7 +3088,8 @@ static inline int vfs_lstat(const char __user *name, struct kstat *stat) static inline int vfs_fstatat(int dfd, const char __user *filename, struct kstat *stat, int flags) { - return vfs_statx(dfd, filename, flags, stat, STATX_BASIC_STATS); + return vfs_statx(dfd, filename, flags | AT_NO_AUTOMOUNT, + stat, STATX_BASIC_STATS); } static inline int vfs_fstat(int fd, struct kstat *stat) {