I audited gnulib's uses of fstatat and found one fishy one that doesn't
use AT_NO_AUTOMOUNT, namely, in fts.c where the follow-symlink branch
uses 'stat' whereas the no-follow-symlink branch uses fstatat without
AT_NO_AUTOMOUNT. I installed the first patch to cause it be consistent
in using AT_NO_AUTOMOUNT, which is also consistent with what glibc does
(though this doesn't necessarily mean it's right - perhaps fts should
have a new flag to control automounts, depending on what the user wants).
The second attached patch deprecates statat and lstatat, due to the
confusion already mentioned.
I haven't audited Gnulib's uses of 'stat' and 'lstat'.From 44f347ce4009cd0100d0e6562939a032b16d6db1 Mon Sep 17 00:00:00 2001
From: Paul Eggert
Date: Wed, 9 Mar 2022 11:54:13 -0800
Subject: [PATCH 1/2] fts: be consistent about AT_NO_AUTOMOUNT
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit
* lib/fts.c (fts_stat): Use fstatat with AT_NO_AUTOMOUNT
consistently, instead of sometimes using stat (which implies
AT_NO_AUTOMOUNT) and sometimes using fstatat without AT_NO_AUTOMOUNT.
Remove a goto while we’re at it.
---
ChangeLog | 8
lib/fts.c | 34 +-
2 files changed, 25 insertions(+), 17 deletions(-)
diff --git a/ChangeLog b/ChangeLog
index e3f0ed216c..58873a1762 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,11 @@
+2022-03-09 Paul Eggert
+
+ fts: be consistent about AT_NO_AUTOMOUNT
+ * lib/fts.c (fts_stat): Use fstatat with AT_NO_AUTOMOUNT
+ consistently, instead of sometimes using stat (which implies
+ AT_NO_AUTOMOUNT) and sometimes using fstatat without AT_NO_AUTOMOUNT.
+ Remove a goto while we’re at it.
+
2022-03-07 Pádraig Brady
fcntl-h: add AT_NO_AUTOMOUNT
diff --git a/lib/fts.c b/lib/fts.c
index 706c56c597..a1a7c09fdb 100644
--- a/lib/fts.c
+++ b/lib/fts.c
@@ -1766,7 +1766,8 @@ fts_stat(FTS *sp, register FTSENT *p, bool follow)
{
struct stat *sbp = p->fts_statp;
-if (p->fts_level == FTS_ROOTLEVEL && ISSET(FTS_COMFOLLOW))
+if (ISSET (FTS_LOGICAL)
+|| (ISSET (FTS_COMFOLLOW) && p->fts_level == FTS_ROOTLEVEL))
follow = true;
/*
@@ -1774,22 +1775,21 @@ fts_stat(FTS *sp, register FTSENT *p, bool follow)
* a stat(2). If that fails, check for a non-existent symlink. If
* fail, set the errno from the stat call.
*/
-if (ISSET(FTS_LOGICAL) || follow) {
-if (stat(p->fts_accpath, sbp)) {
-if (errno == ENOENT
-&& lstat(p->fts_accpath, sbp) == 0) {
-__set_errno (0);
-return (FTS_SLNONE);
-}
-p->fts_errno = errno;
-goto err;
-}
-} else if (fstatat(sp->fts_cwd_fd, p->fts_accpath, sbp,
- AT_SYMLINK_NOFOLLOW)) {
-p->fts_errno = errno;
-err:memset(sbp, 0, sizeof(struct stat));
-return (FTS_NS);
-}
+int flags = (follow ? 0 : AT_SYMLINK_NOFOLLOW) | AT_NO_AUTOMOUNT;
+if (fstatat (sp->fts_cwd_fd, p->fts_accpath, sbp, flags) < 0)
+ {
+if (follow && errno == ENOENT
+&& 0 <= fstatat (sp->fts_cwd_fd, p->fts_accpath, sbp,
+ AT_SYMLINK_NOFOLLOW | AT_NO_AUTOMOUNT))
+ {
+__set_errno (0);
+return FTS_SLNONE;
+ }
+
+p->fts_errno = errno;
+memset (sbp, 0, sizeof *sbp);
+return FTS_NS;
+ }
if (S_ISDIR(sbp->st_mode)) {
if (ISDOT(p->fts_name)) {
--
2.35.1
From eea9688d521634c58efa81130e509f647bbd9ff9 Mon Sep 17 00:00:00 2001
From: Paul Eggert
Date: Wed, 9 Mar 2022 13:54:53 -0800
Subject: [PATCH 2/2] statat: now obsolete
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit
* lib/openat.h (statat, lstatat): Now deprecated.
All uses removed, and replaced with fstatat.
* modules/statat: Mark as obsolete, because it’s confusing:
it’s not clear whether it should use AT_NO_AUTOMOUNT,
which is implied by stat and by lstat, but not by fstatat.
* tests/test-statat.c: Disable deprecated-declarations warnings.
---
ChangeLog | 8
NEWS| 3 +++
lib/fchownat.c | 2 +-
lib/openat.h| 2 ++
lib/renameatu.c | 15 ---
lib/unlinkat.c | 5 +++--
modules/fchownat| 1 -
modules/renameatu | 1 -
modules/statat | 7 +++
modules/unlinkat| 1 -
tests/test-statat.c | 4
11 files changed, 36 insertions(+), 13 deletions(-)
diff --git a/ChangeLog b/ChangeLog
index 58873a1762..294f6286f3 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,5 +1,13 @@
2022-03-09 Paul Eggert
+ statat: now obsolete
+ * lib/openat.h (statat,
