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=== Description (from pull-request) ===
This makes running lxcfs way more reliable. It is opt-in for now.
Signed-off-by: Christian Brauner <christian.brau...@ubuntu.com>
From 20400f482bb66a5312a2dfaa2be4220184f590e5 Mon Sep 17 00:00:00 2001
From: Christian Brauner <christian.brau...@ubuntu.com>
Date: Wed, 26 Feb 2020 14:08:08 +0100
Subject: [PATCH] lxcfs: add --pidfd option
This makes running lxcfs way more reliable. It is opt-in for now.
Signed-off-by: Christian Brauner <christian.brau...@ubuntu.com>
---
Makefile.am | 2 +-
bindings.c | 210 +++++++++++++++++++++++++++++++--------------------
bindings.h | 5 +-
configure.ac | 10 +++
lxcfs.c | 4 +
utils.h | 23 ++++++
6 files changed, 171 insertions(+), 83 deletions(-)
diff --git a/Makefile.am b/Makefile.am
index 41f3249..5f64cfb 100644
--- a/Makefile.am
+++ b/Makefile.am
@@ -7,7 +7,7 @@ AM_CFLAGS = -Wall -ggdb -D_GNU_SOURCE -DSBINDIR=\"$(SBINDIR)\"
-pthread
AM_CFLAGS += $(FUSE_CFLAGS)
AM_CFLAGS += -DLIBDIR=\"$(LIBDIR)\"
AM_LDFLAGS = $(FUSE_LIBS) -pthread
-#AM_CFLAGS += -DDEBUG
+AM_CFLAGS += -DDEBUG
#AM_CFLAGS += -DVERBOSE
AM_CFLAGS += -DRUNTIME_PATH=\"$(RUNTIME_PATH)\"
diff --git a/bindings.c b/bindings.c
index 7bf5d28..f5a6415 100644
--- a/bindings.c
+++ b/bindings.c
@@ -53,6 +53,8 @@
#include "proc_cpuview.h"
#include "utils.h"
+static bool can_use_pidfd;
+
/* Define pivot_root() if missing from the C library */
#ifndef HAVE_PIVOT_ROOT
static int pivot_root(const char *new_root, const char *put_old)
@@ -83,9 +85,10 @@ extern int pivot_root(const char *new_root, const char
*put_old);
* cached initpid.
*/
struct pidns_init_store {
- ino_t ino; // inode number for /proc/$pid/ns/pid
- pid_t initpid; // the pid of nit in that ns
- long int ctime; // the time at which /proc/$initpid was created
+ ino_t ino; /* inode number for /proc/$pid/ns/pid */
+ pid_t initpid; /* the pid of nit in that ns */
+ int init_pidfd;
+ long int ctime; /* the time at which /proc/$initpid was created */
struct pidns_init_store *next;
long int lastcheck;
};
@@ -127,47 +130,62 @@ static void store_unlock(void)
unlock_mutex(&pidns_store_mutex);
}
+/* /proc/ = 6
+ * +
+ * <pid-as-str> = INTTYPE_TO_STRLEN(pid_t)
+ * +
+ * \0 = 1
+ */
+#define LXCFS_PROC_PID_LEN \
+ (STRLITERALLEN("/proc/") + INTTYPE_TO_STRLEN(uint64_t) + +1)
+
/* Must be called under store_lock */
-static bool initpid_still_valid(struct pidns_init_store *e, struct stat
*nsfdsb)
+static bool initpid_still_valid(struct pidns_init_store *entry)
{
- struct stat initsb;
- char fnam[100];
+ bool valid = true;
- snprintf(fnam, 100, "/proc/%d", e->initpid);
- if (stat(fnam, &initsb) < 0)
- return false;
+ if (entry->init_pidfd >= 0) {
+ if (pidfd_send_signal(entry->init_pidfd, 0, NULL, 0))
+ valid = false;
+ } else {
+ struct stat st;
+ char path[LXCFS_PROC_PID_LEN];
- lxcfs_debug("Comparing ctime %ld == %ld for pid %d.\n", e->ctime,
- initsb.st_ctime, e->initpid);
+ snprintf(path, sizeof(path), "/proc/%d", entry->initpid);
- if (e->ctime != initsb.st_ctime)
- return false;
- return true;
+ if (stat(path, &st) || entry->ctime != st.st_ctime)
+ valid = false;
+ }
+
+ return valid;
}
/* Must be called under store_lock */
-static void remove_initpid(struct pidns_init_store *e)
+static void remove_initpid(struct pidns_init_store *entry)
{
- struct pidns_init_store *tmp;
- int h;
+ struct pidns_init_store *it;
+ int ino_hash;
- lxcfs_debug("Remove_initpid: removing entry for %d.\n", e->initpid);
+ lxcfs_debug("Removing cached entry for pid %d from init pid cache",
+ entry->initpid);
- h = HASH(e->ino);
- if (pidns_hash_table[h] == e) {
- pidns_hash_table[h] = e->next;
- free_disarm(e);
+ ino_hash = HASH(entry->ino);
+ if (pidns_hash_table[ino_hash] == entry) {
+ pidns_hash_table[ino_hash] = entry->next;
+ close_prot_errno_disarm(entry->init_pidfd);
+ free_disarm(entry);
return;
}
- tmp = pidns_hash_table[h];
- while (tmp) {
- if (tmp->next == e) {
- tmp->next = e->next;
- free_disarm(e);
+ it = pidns_hash_table[ino_hash];
+ while (it) {
+ if (it->next == entry) {
+ it->next = entry->next;
+ close_prot_errno_disarm(entry->init_pidfd);
+ free_disarm(entry);
return;
}
- tmp = tmp->next;
+ it = it->next;
}
}
@@ -176,39 +194,39 @@ static void remove_initpid(struct pidns_init_store *e)
static void prune_initpid_store(void)
{
static long int last_prune = 0;
- struct pidns_init_store *e, *prev, *delme;
long int now, threshold;
- int i;
if (!last_prune) {
last_prune = time(NULL);
return;
}
+
now = time(NULL);
if (now < last_prune + PURGE_SECS)
return;
- lxcfs_debug("%s\n", "Pruning.");
+ lxcfs_debug("Pruning init pid cache");
last_prune = now;
threshold = now - 2 * PURGE_SECS;
- for (i = 0; i < PIDNS_HASH_SIZE; i++) {
- for (prev = NULL, e = pidns_hash_table[i]; e; ) {
- if (e->lastcheck < threshold) {
+ for (int i = 0; i < PIDNS_HASH_SIZE; i++) {
+ for (struct pidns_init_store *entry = pidns_hash_table[i],
*prev = NULL; entry;) {
+ if (entry->lastcheck < threshold) {
+ struct pidns_init_store *cur = entry;
- lxcfs_debug("Removing cached entry for %d.\n",
e->initpid);
+ lxcfs_debug("Removed cache entry for pid %d to
init pid cache", cur->initpid);
- delme = e;
if (prev)
- prev->next = e->next;
+ prev->next = entry->next;
else
- pidns_hash_table[i] = e->next;
- e = e->next;
- free_disarm(delme);
+ pidns_hash_table[i] = entry->next;
+ entry = entry->next;
+ close_prot_errno_disarm(cur->init_pidfd);
+ free_disarm(cur);
} else {
- prev = e;
- e = e->next;
+ prev = entry;
+ entry = entry->next;
}
}
}
@@ -217,26 +235,37 @@ static void prune_initpid_store(void)
/* Must be called under store_lock */
static void save_initpid(struct stat *sb, pid_t pid)
{
- struct pidns_init_store *e;
- char fpath[100];
- struct stat procsb;
- int h;
+ __do_free struct pidns_init_store *e = NULL;
+ __do_close_prot_errno int pidfd = -EBADF;
+ char path[LXCFS_PROC_PID_LEN];
+ struct lxcfs_opts *opts = fuse_get_context()->private_data;
+ struct stat st;
+ int ino_hash;
+
+ if (opts->use_pidfd && can_use_pidfd) {
+ pidfd = pidfd_open(pid, 0);
+ if (pidfd < 0)
+ return;
+ }
- lxcfs_debug("Save_initpid: adding entry for %d.\n", pid);
+ snprintf(path, sizeof(path), "/proc/%d", pid);
+ if (stat(path, &st))
+ return;
- snprintf(fpath, 100, "/proc/%d", pid);
- if (stat(fpath, &procsb) < 0)
+ e = malloc(sizeof(*e));
+ if (!e)
return;
- do {
- e = malloc(sizeof(*e));
- } while (!e);
+
e->ino = sb->st_ino;
e->initpid = pid;
- e->ctime = procsb.st_ctime;
- h = HASH(e->ino);
- e->next = pidns_hash_table[h];
+ e->ctime = st.st_ctime;
+ ino_hash = HASH(e->ino);
+ e->next = pidns_hash_table[ino_hash];
e->lastcheck = time(NULL);
- pidns_hash_table[h] = e;
+ e->init_pidfd = move_fd(pidfd);
+ pidns_hash_table[ino_hash] = move_ptr(e);
+
+ lxcfs_debug("Added cache entry %d for pid %d to init pid cache",
ino_hash, pid);
}
/*
@@ -248,19 +277,19 @@ static void save_initpid(struct stat *sb, pid_t pid)
*/
static struct pidns_init_store *lookup_verify_initpid(struct stat *sb)
{
- int h = HASH(sb->st_ino);
- struct pidns_init_store *e = pidns_hash_table[h];
-
- while (e) {
- if (e->ino == sb->st_ino) {
- if (initpid_still_valid(e, sb)) {
- e->lastcheck = time(NULL);
- return e;
+ struct pidns_init_store *entry = pidns_hash_table[HASH(sb->st_ino)];
+
+ while (entry) {
+ if (entry->ino == sb->st_ino) {
+ if (initpid_still_valid(entry)) {
+ entry->lastcheck = time(NULL);
+ return entry;
}
- remove_initpid(e);
+
+ remove_initpid(entry);
return NULL;
}
- e = e->next;
+ entry = entry->next;
}
return NULL;
@@ -358,31 +387,42 @@ static pid_t get_init_pid_for_task(pid_t task)
return ret;
}
-pid_t lookup_initpid_in_store(pid_t qpid)
+#define LXCFS_PROC_PID_NS_LEN \
+ (STRLITERALLEN("/proc/") + INTTYPE_TO_STRLEN(uint64_t) + \
+ STRLITERALLEN("/ns/pid") + 1)
+
+pid_t lookup_initpid_in_store(pid_t pid)
{
pid_t answer = 0;
- struct stat sb;
- struct pidns_init_store *e;
- char fnam[100];
+ char path[LXCFS_PROC_PID_NS_LEN];
+ struct stat st;
+ struct pidns_init_store *entry;
+
+ snprintf(path, sizeof(path), "/proc/%d/ns/pid", pid);
- snprintf(fnam, 100, "/proc/%d/ns/pid", qpid);
store_lock();
- if (stat(fnam, &sb) < 0)
+ if (stat(path, &st))
goto out;
- e = lookup_verify_initpid(&sb);
- if (e) {
- answer = e->initpid;
+
+ entry = lookup_verify_initpid(&st);
+ if (entry) {
+ answer = entry->initpid;
goto out;
}
- answer = get_init_pid_for_task(qpid);
+
+ answer = get_init_pid_for_task(pid);
if (answer > 0)
- save_initpid(&sb, answer);
+ save_initpid(&st, answer);
out:
- /* we prune at end in case we are returning
- * the value we were about to return */
+ /*
+ * Prune at the end in case we're returning the value we were about to
+ * return.
+ */
prune_initpid_store();
+
store_unlock();
+
return answer;
}
@@ -663,8 +703,9 @@ static bool cgfs_setup_controllers(void)
static void __attribute__((constructor)) lxcfs_init(void)
{
- __do_close_prot_errno int init_ns = -EBADF;
+ __do_close_prot_errno int init_ns = -EBADF, pidfd = -EBADF;
int i = 0;
+ pid_t pid;
char *cret;
char cwd[MAXPATHLEN];
@@ -673,7 +714,8 @@ static void __attribute__((constructor)) lxcfs_init(void)
log_exit("Failed to initialize cgroup support");
/* Preserve initial namespace. */
- init_ns = preserve_ns(getpid(), "mnt");
+ pid = getpid();
+ init_ns = preserve_ns(pid, "mnt");
if (init_ns < 0)
log_exit("Failed to preserve initial mount namespace");
@@ -702,6 +744,12 @@ static void __attribute__((constructor)) lxcfs_init(void)
__do_free char *controllers = lxc_string_join(",", (const char
**)(*h)->controllers, false);
fprintf(stderr, " %2d: fd: %3d: %s\n", i, (*h)->fd, controllers
?: "");
}
+
+ pidfd = pidfd_open(pid, 0);
+ if (pidfd >= 0 && pidfd_send_signal(pidfd, 0, NULL, 0) == 0) {
+ can_use_pidfd = true;
+ lxcfs_error("Kernel supports pidfds");
+ }
}
static void __attribute__((destructor)) lxcfs_exit(void)
diff --git a/bindings.h b/bindings.h
index 8e330ec..777fcd2 100644
--- a/bindings.h
+++ b/bindings.h
@@ -14,15 +14,16 @@
#define _FILE_OFFSET_BITS 64
#include <fuse.h>
+#include <stdbool.h>
#include <stdio.h>
#include <stdlib.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <unistd.h>
+#include "cgroup_fuse.h"
#include "config.h"
#include "macro.h"
-#include "cgroup_fuse.h"
#include "proc_cpuview.h"
#include "proc_fuse.h"
#include "proc_loadavg.h"
@@ -64,9 +65,11 @@ struct file_info {
struct lxcfs_opts {
bool swap_off;
+ bool use_pidfd;
};
extern pid_t lookup_initpid_in_store(pid_t qpid);
extern void prune_init_slice(char *cg);
+extern bool supports_pidfd(void);
#endif /* __LXCFS_BINDINGS_H */
diff --git a/configure.ac b/configure.ac
index 63cd934..e22cf3c 100644
--- a/configure.ac
+++ b/configure.ac
@@ -171,4 +171,14 @@ AC_CHECK_FUNCS([strlcat],
AC_DEFINE(HAVE_STRLCAT,1,[Have strlcat]),
AM_CONDITIONAL(HAVE_STRLCAT, false))
+AC_CHECK_FUNCS([pidfd_open],
+ AM_CONDITIONAL(HAVE_PIDFD_OPEN, true)
+ AC_DEFINE(HAVE_PIDFD_OPEN,1,[Supports pidfd_open]),
+ AM_CONDITIONAL(HAVE_PIDFD_OPEN, false))
+
+AC_CHECK_FUNCS([pidfd_send_signal],
+ AM_CONDITIONAL(HAVE_PIDFD_SEND_SIGNAL, true)
+ AC_DEFINE(HAVE_PIDFD_SEND_SIGNAL,1,[Supports pidfd_send_signal]),
+ AM_CONDITIONAL(HAVE_PIDFD_SEND_SIGNAL, false))
+
AC_OUTPUT
diff --git a/lxcfs.c b/lxcfs.c
index ce5a24b..d825303 100644
--- a/lxcfs.c
+++ b/lxcfs.c
@@ -1102,6 +1102,7 @@ int main(int argc, char *argv[])
goto out;
}
opts->swap_off = false;
+ opts->use_pidfd = false;
/* accomodate older init scripts */
swallow_arg(&argc, argv, "-s");
@@ -1112,6 +1113,9 @@ int main(int argc, char *argv[])
if (swallow_arg(&argc, argv, "-u"))
opts->swap_off = true;
+ if (swallow_arg(&argc, argv, "--pidfd"))
+ opts->use_pidfd = true;
+
if (swallow_option(&argc, argv, "-o", &v)) {
/* Parse multiple values */
for (; (token = strtok_r(v, ",", &saveptr)); v = NULL) {
diff --git a/utils.h b/utils.h
index 6c874b4..d5673ed 100644
--- a/utils.h
+++ b/utils.h
@@ -46,4 +46,27 @@ extern int read_file_fuse(const char *path, char *buf,
size_t size,
extern void prune_init_slice(char *cg);
extern int wait_for_pid(pid_t pid);
+#ifndef HAVE_PIDFD_OPEN
+static inline int pidfd_open(pid_t pid, unsigned int flags)
+{
+#ifdef __NR_pidfd_open
+ return syscall(__NR_pidfd_open, pid, flags);
+#else
+ return ret_errno(ENOSYS);
+#endif
+}
+#endif
+
+#ifndef HAVE_PIDFD_SEND_SIGNAL
+static inline int pidfd_send_signal(int pidfd, int sig, siginfo_t *info,
+ unsigned int flags)
+{
+#ifdef __NR_pidfd_send_signal
+ return syscall(__NR_pidfd_send_signal, pidfd, sig, info, flags);
+#else
+ return ret_errno(ENOSYS);
+#endif
+}
+#endif
+
#endif /* __LXCFS_UTILS_H */
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