From: Chuck Lever III <chuck.lever@oracle.com>
To: Jeff Layton <jlayton@kernel.org>
Cc: Steve Dickson <steved@redhat.com>,
Linux NFS Mailing List <linux-nfs@vger.kernel.org>,
JianHong Yin <jiyin@redhat.com>
Subject: Re: [nfs-utils PATCH] Don't allow junction tests to trigger automounts
Date: Tue, 13 Dec 2022 16:25:56 +0000 [thread overview]
Message-ID: <52DA8A58-FF23-4528-B094-D8849D1DE54A@oracle.com> (raw)
In-Reply-To: <20221213160104.198237-1-jlayton@kernel.org>
> On Dec 13, 2022, at 11:01 AM, Jeff Layton <jlayton@kernel.org> wrote:
>
> JianHong reported some strange behavior with automounts on an nfs server
> without an explicit pseudoroot. When clients issued a readdir in the
> pseudoroot, automounted directories that were not yet mounted would show
> up even if they weren't exported, though the clients wouldn't be able to
> do anything with them.
>
> The issue was that triggering the automount on a directory would cause
> the mountd upcall to time out, which would cause nfsd to include the
> automounted dentry in the readdir response. Eventually, the automount
> would work and report that it wasn't exported and subsequent attempts to
> access the dentry would (properly) fail.
>
> We never want mountd to trigger an automount. The kernel should do that
> if it wants to use it. Change the junction checks to do an O_PATH open
> and use fstatat with AT_NO_AUTOMOUNT.
>
> Cc: Chuck Lever <chuck.lever@oracle.com>
> Link: https://bugzilla.redhat.com/show_bug.cgi?id=2148353
And also https://bugzilla.kernel.org/show_bug.cgi?id=216777 ?
> Reported-by: JianHong Yin <jiyin@redhat.com>
> Signed-off-by: Jeff Layton <jlayton@kernel.org>
> ---
> support/junction/junction.c | 10 +++++-----
> 1 file changed, 5 insertions(+), 5 deletions(-)
>
> diff --git a/support/junction/junction.c b/support/junction/junction.c
> index 41cce261cb52..0628bb0ffffb 100644
> --- a/support/junction/junction.c
> +++ b/support/junction/junction.c
> @@ -63,7 +63,7 @@ junction_open_path(const char *pathname, int *fd)
> if (pathname == NULL || fd == NULL)
> return FEDFS_ERR_INVAL;
>
> - tmp = open(pathname, O_DIRECTORY);
> + tmp = open(pathname, O_PATH|O_DIRECTORY);
> if (tmp == -1) {
> switch (errno) {
> case EPERM:
> @@ -93,7 +93,7 @@ junction_is_directory(int fd, const char *path)
> {
> struct stat stb;
>
> - if (fstat(fd, &stb) == -1) {
> + if (fstatat(fd, "", &stb, AT_NO_AUTOMOUNT|AT_EMPTY_PATH) == -1) {
> xlog(D_GENERAL, "%s: failed to stat %s: %m",
> __func__, path);
> return FEDFS_ERR_ACCESS;
> @@ -121,7 +121,7 @@ junction_is_sticky_bit_set(int fd, const char *path)
> {
> struct stat stb;
>
> - if (fstat(fd, &stb) == -1) {
> + if (fstatat(fd, "", &stb, AT_NO_AUTOMOUNT|AT_EMPTY_PATH) == -1) {
> xlog(D_GENERAL, "%s: failed to stat %s: %m",
> __func__, path);
> return FEDFS_ERR_ACCESS;
> @@ -155,7 +155,7 @@ junction_set_sticky_bit(int fd, const char *path)
> {
> struct stat stb;
>
> - if (fstat(fd, &stb) == -1) {
> + if (fstatat(fd, "", &stb, AT_NO_AUTOMOUNT|AT_EMPTY_PATH) == -1) {
> xlog(D_GENERAL, "%s: failed to stat %s: %m",
> __func__, path);
> return FEDFS_ERR_ACCESS;
> @@ -393,7 +393,7 @@ junction_get_mode(const char *pathname, mode_t *mode)
> if (retval != FEDFS_OK)
> return retval;
>
> - if (fstat(fd, &stb) == -1) {
> + if (fstatat(fd, "", &stb, AT_NO_AUTOMOUNT|AT_EMPTY_PATH) == -1) {
> xlog(D_GENERAL, "%s: failed to stat %s: %m",
> __func__, pathname);
> (void)close(fd);
> --
> 2.38.1
>
--
Chuck Lever
next prev parent reply other threads:[~2022-12-13 16:26 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-12-13 16:01 [nfs-utils PATCH] Don't allow junction tests to trigger automounts Jeff Layton
2022-12-13 16:25 ` Chuck Lever III [this message]
2022-12-13 16:41 ` Jeff Layton
2023-01-04 12:23 ` Jeff Layton
2023-01-11 15:55 ` Steve Dickson
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