> On Dec 13, 2022, at 11:01 AM, Jeff Layton <jlayton@xxxxxxxxxx> 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@xxxxxxxxxx> > 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@xxxxxxxxxx> > Signed-off-by: Jeff Layton <jlayton@xxxxxxxxxx> > --- > 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
