ci: add Valgrind memcheck job

- Add valgrind-memcheck job running full pytest suite under memcheck with continue-on-error: true
- Uses --error-exitcode=99 with definite/indirect leak checking
- Currently finding real sshfs-owned leaks (buf_init/sftp_read, buf_init/sftp_send_iov, cache_add_link) — will go green once those are fixed
- Raw Valgrind logs written via --log-file and uploaded as artifacts alongside JUnit XML
- Add VALGRIND_OPTIONS support to test/util.py via shlex.split
- Suppression file covers only third-party libfuse worker-thread teardown leaks
- Fix fusermount/fusermount3 mismatch, scale timeouts 4x under Valgrind
- Set G_DEBUG/G_SLICE for cleaner Valgrind output
- Hard-fail FUSE preflight, workflow-level permissions and concurrency
- All actions pinned to Node 24-capable SHAs, runner pinned to ubuntu-24.04

Author: abhinavagarwal07

test/conftest.py

@@ -1,4 +1,5 @@
 import sys
+import os
 import pytest
 import time
 import re
@@ -85,6 +86,13 @@ def register_output(self, pattern, count=1, flags=re.MULTILINE):
 current_capfd = None
 
 
+_running_with_valgrind = os.environ.get("TEST_WITH_VALGRIND", "no").lower().strip() not in (
+    "no",
+    "false",
+    "0",
+)
+
+
 @pytest.fixture(autouse=True)
 def save_cap_fixtures(request, capfd):
     global current_capfd
@@ -93,6 +101,12 @@ def save_cap_fixtures(request, capfd):
     # Monkeypatch in a function to register false positives
     type(capfd).register_output = register_output
 
+    # When running under Valgrind, its ==pid== summary lines on stderr are
+    # expected. Register them as false positives so check_test_output does
+    # not mistake them for suspicious output.
+    if _running_with_valgrind:
+        capfd.false_positives.append((r"^==[0-9]+==[^\n]*\n", re.MULTILINE, 0))
+
     if request.config.getoption("capture") == "no":
         capfd = None
     current_capfd = capfd

test/util.py

@@ -9,6 +9,14 @@
 
 basename = pjoin(os.path.dirname(__file__), "..")
 
+_valgrind_timeout_multiplier = (
+    4
+    if os.environ.get("TEST_WITH_VALGRIND", "no").lower().strip()
+    not in ("no", "false", "0")
+    else 1
+)
+_mount_timeout = 30 * _valgrind_timeout_multiplier
+
 
 def os_create(name):
     os.close(os.open(name, os.O_CREAT | os.O_RDWR))
@@ -25,7 +33,7 @@ def os_open(name, flags):
 
 def wait_for_mount(mount_process, mnt_dir, test_fn=os.path.ismount):
     elapsed = 0
-    while elapsed < 30:
+    while elapsed < _mount_timeout:
         if test_fn(mnt_dir):
             return True
         if mount_process.poll() is not None:
@@ -37,7 +45,7 @@ def wait_for_mount(mount_process, mnt_dir, test_fn=os.path.ismount):
 
 def cleanup(mount_process, mnt_dir):
     subprocess.call(
-        ["fusermount", "-z", "-u", mnt_dir],
+        ["fusermount3", "-z", "-u", mnt_dir],
         stdout=subprocess.DEVNULL,
         stderr=subprocess.STDOUT,
     )
@@ -55,7 +63,7 @@ def umount(mount_process, mnt_dir):
     # Give mount process a little while to terminate. Popen.wait(timeout)
     # was only added in 3.3...
     elapsed = 0
-    while elapsed < 30:
+    while elapsed < _mount_timeout:
         code = mount_process.poll()
         if code is not None:
             if code == 0:
@@ -93,12 +101,12 @@ def skip(reason: str):
         return pytest.mark.skip(reason=reason)
 
     with subprocess.Popen(
-        ["which", "fusermount"], stdout=subprocess.PIPE, universal_newlines=True
+        ["which", "fusermount3"], stdout=subprocess.PIPE, universal_newlines=True
     ) as which:
         fusermount_path = which.communicate()[0].strip()
 
     if not fusermount_path or which.returncode != 0:
-        return skip("Can't find fusermount executable")
+        return skip("Can't find fusermount3 executable")
 
     if not os.path.exists("/dev/fuse"):
         return skip("FUSE kernel module does not seem to be loaded")
@@ -126,6 +134,11 @@ def skip(reason: str):
     "false",
     "0",
 ):
-    base_cmdline = ["valgrind", "-q", "--"]
+    import shlex
+    valgrind_options_env = os.environ.get("VALGRIND_OPTIONS", "")
+    if valgrind_options_env:
+        base_cmdline = ["valgrind"] + shlex.split(valgrind_options_env) + ["--"]
+    else:
+        base_cmdline = ["valgrind", "-q", "--"]
 else:
     base_cmdline = []

test/valgrind.supp

@@ -0,0 +1,25 @@
+# Valgrind suppression file for sshfs tests.
+#
+# Keep this file minimal. Only suppress stacks that originate entirely in
+# third-party libraries (GLib, libfuse, glibc, pthreads) and have been
+# confirmed as false positives or benign teardown noise.
+#
+# Do NOT suppress any stack frame that includes sshfs.c or cache.c unless
+# there is a documented upstream false positive with a linked note below.
+#
+# To generate candidates locally:
+#   TEST_WITH_VALGRIND=true VALGRIND_OPTIONS="--tool=memcheck --leak-check=full \
+#     --gen-suppressions=all -q --" python3 -m pytest test/test_sshfs.py ...
+
+# libfuse allocates thread-local or worker-thread state inside its shared
+# library during pthread_create. These are not reachable after the threads
+# exit but are never explicitly freed — they are benign teardown leaks in
+# libfuse internals, not sshfs bugs.
+{
+   libfuse-worker-thread-alloc
+   Memcheck:Leak
+   match-leak-kinds: definite,indirect
+   fun:calloc
+   ...
+   obj:*/libfuse3.so*
+}