liblxcfs: handle broken upgrade gracefully

Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>
lxc · Mar 13, 2020 · 920f887 · 920f887
1 parent 2c7dd60
commit 920f887
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Showing 7 changed files with 129 additions and 11 deletions.
diff --git a/src/bindings.c b/src/bindings.c
@@ -50,6 +50,12 @@
 #include "utils.h"
 
 static bool can_use_pidfd;
+static bool reload_successful;
+
+bool liblxcfs_functional(void)
+{
+	return reload_successful;
+}
 
 /* Define pivot_root() if missing from the C library */
 #ifndef HAVE_PIVOT_ROOT
@@ -722,7 +728,7 @@ static void __attribute__((constructor)) lxcfs_init(void)
 	int i = 0;
 	pid_t pid;
 
-	lxcfs_info("Running constructor %s to reload liblxcfs with count", __func__);
+	lxcfs_info("Running constructor %s to reload liblxcfs", __func__);
 
 	cgroup_ops = cgroup_init();
 	if (!cgroup_ops) {
@@ -782,9 +788,11 @@ static void __attribute__((constructor)) lxcfs_init(void)
 	else if (fchdir(root_fd) < 0)
 		lxcfs_info("%s - Failed to change to root directory", strerror(errno));
 
+	reload_successful = true;
 	return;
 
 broken_upgrade:
+	reload_successful = false;
 	lxcfs_info("Failed to run constructor %s to reload liblxcfs", __func__);
 }
 

diff --git a/src/bindings.h b/src/bindings.h
@@ -39,17 +39,34 @@
 enum lxcfs_virt_t {
 	LXC_TYPE_CGDIR,
 	LXC_TYPE_CGFILE,
+
 	LXC_TYPE_PROC_MEMINFO,
+#define LXC_TYPE_PROC_MEMINFO_PATH "/proc/meminfo"
+
 	LXC_TYPE_PROC_CPUINFO,
+#define LXC_TYPE_PROC_CPUINFO_PATH "/proc/cpuinfo"
+
 	LXC_TYPE_PROC_UPTIME,
+#define LXC_TYPE_PROC_UPTIME_PATH "/proc/uptime"
+
 	LXC_TYPE_PROC_STAT,
+#define LXC_TYPE_PROC_STAT_PATH "/proc/stat"
+
 	LXC_TYPE_PROC_DISKSTATS,
+#define LXC_TYPE_PROC_DISKSTATS_PATH "/proc/diskstats"
+
 	LXC_TYPE_PROC_SWAPS,
+#define LXC_TYPE_PROC_SWAPS_PATH "/proc/swaps"
+
 	LXC_TYPE_PROC_LOADAVG,
+#define LXC_TYPE_PROC_LOADAVG_PATH "/proc/loadavg"
+
 	LXC_TYPE_SYS_DEVICES,
 	LXC_TYPE_SYS_DEVICES_SYSTEM,
 	LXC_TYPE_SYS_DEVICES_SYSTEM_CPU,
+
 	LXC_TYPE_SYS_DEVICES_SYSTEM_CPU_ONLINE,
+#define LXC_TYPE_SYS_DEVICES_SYSTEM_CPU_ONLINE_PATH "/sys/devices/system/cpu/online"
 };
 
 struct file_info {
@@ -72,5 +89,6 @@ struct lxcfs_opts {
 extern pid_t lookup_initpid_in_store(pid_t qpid);
 extern void prune_init_slice(char *cg);
 extern bool supports_pidfd(void);
+extern bool liblxcfs_functional(void);
 
 #endif /* __LXCFS_BINDINGS_H */
diff --git a/src/cgroup_fuse.c b/src/cgroup_fuse.c
@@ -510,6 +510,8 @@ __lxcfs_fuse_ops int cg_getattr(const char *path, struct stat *sb)
 	const char *controller = NULL;
 	int ret = -ENOENT;
 
+	if (!liblxcfs_functional())
+		return -EIO;
 
 	if (!fc || !cgroup_ops || pure_unified_layout(cgroup_ops))
 		return -EIO;
@@ -689,6 +691,9 @@ __lxcfs_fuse_ops int cg_mkdir(const char *path, mode_t mode)
 	const char *cgroup;
 	int ret;
 
+	if (!liblxcfs_functional())
+		return -EIO;
+
 	if (!fc || !cgroup_ops || pure_unified_layout(cgroup_ops))
 		return -EIO;
 
@@ -829,6 +834,9 @@ __lxcfs_fuse_ops int cg_rmdir(const char *path)
 	const char *cgroup;
 	int ret;
 
+	if (!liblxcfs_functional())
+		return -EIO;
+
 	if (!fc || !cgroup_ops || pure_unified_layout(cgroup_ops))
 		return -EIO;
 
@@ -912,6 +920,9 @@ __lxcfs_fuse_ops int cg_chmod(const char *path, mode_t mode)
 	const char *cgroup;
 	int ret;
 
+	if (!liblxcfs_functional())
+		return -EIO;
+
 	if (!fc || !cgroup_ops || pure_unified_layout(cgroup_ops))
 		return -EIO;
 
@@ -1032,6 +1043,9 @@ __lxcfs_fuse_ops int cg_chown(const char *path, uid_t uid, gid_t gid)
 	const char *cgroup;
 	int ret;
 
+	if (!liblxcfs_functional())
+		return -EIO;
+
 	if (!fc || !cgroup_ops || pure_unified_layout(cgroup_ops))
 		return -EIO;
 
@@ -1099,6 +1113,9 @@ __lxcfs_fuse_ops int cg_open(const char *path, struct fuse_file_info *fi)
 	struct fuse_context *fc = fuse_get_context();
 	int ret;
 
+	if (!liblxcfs_functional())
+		return -EIO;
+
 	if (!fc || !cgroup_ops || pure_unified_layout(cgroup_ops))
 		return -EIO;
 
@@ -1364,6 +1381,9 @@ __lxcfs_fuse_ops int cg_read(const char *path, char *buf, size_t size,
 	int ret, s;
 	bool r;
 
+	if (!liblxcfs_functional())
+		return -EIO;
+
 	if (!fc || !cgroup_ops || pure_unified_layout(cgroup_ops))
 		return -EIO;
 
@@ -1428,6 +1448,9 @@ __lxcfs_fuse_ops int cg_opendir(const char *path, struct fuse_file_info *fi)
 	struct file_info *dir_info;
 	char *controller = NULL;
 
+	if (!liblxcfs_functional())
+		return -EIO;
+
 	if (!fc || !cgroup_ops || pure_unified_layout(cgroup_ops))
 		return -EIO;
 
@@ -1814,6 +1837,9 @@ __lxcfs_fuse_ops int cg_write(const char *path, const char *buf, size_t size,
 	struct file_info *f = INTTYPE_TO_PTR(fi->fh);
 	bool r;
 
+	if (!liblxcfs_functional())
+		return -EIO;
+
 	if (!fc || !cgroup_ops || pure_unified_layout(cgroup_ops))
 		return -EIO;
 
@@ -1985,6 +2011,9 @@ __lxcfs_fuse_ops int cg_readdir(const char *path, void *buf,
 	struct fuse_context *fc = fuse_get_context();
 	char **clist = NULL;
 
+	if (!liblxcfs_functional())
+		return -EIO;
+
 	if (!fc || !cgroup_ops || pure_unified_layout(cgroup_ops))
 		return -EIO;
 
@@ -2075,6 +2104,9 @@ __lxcfs_fuse_ops int cg_access(const char *path, int mode)
 	struct cgfs_files *k = NULL;
 	struct fuse_context *fc = fuse_get_context();
 
+	if (!liblxcfs_functional())
+		return -EIO;
+
 	if (!fc || !cgroup_ops || pure_unified_layout(cgroup_ops))
 		return -EIO;
 

diff --git a/src/proc_fuse.c b/src/proc_fuse.c
@@ -398,7 +398,7 @@ static int proc_diskstats_read(char *buf, size_t size, off_t offset,
 	int ret;
 	char dev_name[72];
 
-	if (offset){
+	if (offset) {
 		int left;
 
 		if (offset > d->size)
@@ -510,7 +510,8 @@ static int proc_diskstats_read(char *buf, size_t size, off_t offset,
 
 	d->cached = 1;
 	d->size = total_len;
-	if (total_len > size ) total_len = size;
+	if (total_len > size)
+		total_len = size;
 	memcpy(buf, d->buf, total_len);
 
 	return total_len;
@@ -1256,19 +1257,47 @@ __lxcfs_fuse_ops int proc_read(const char *path, char *buf, size_t size,
 
 	switch (f->type) {
 	case LXC_TYPE_PROC_MEMINFO:
-		return proc_meminfo_read(buf, size, offset, fi);
+		if (liblxcfs_functional())
+			return proc_meminfo_read(buf, size, offset, fi);
+
+		return read_file_fuse_with_offset(LXC_TYPE_PROC_MEMINFO_PATH,
+						  buf, size, offset, f);
 	case LXC_TYPE_PROC_CPUINFO:
-		return proc_cpuinfo_read(buf, size, offset, fi);
+		if (liblxcfs_functional())
+			return proc_cpuinfo_read(buf, size, offset, fi);
+
+		return read_file_fuse_with_offset(LXC_TYPE_PROC_CPUINFO_PATH,
+						  buf, size, offset, f);
 	case LXC_TYPE_PROC_UPTIME:
-		return proc_uptime_read(buf, size, offset, fi);
+		if (liblxcfs_functional())
+			return proc_uptime_read(buf, size, offset, fi);
+
+		return read_file_fuse_with_offset(LXC_TYPE_PROC_UPTIME_PATH,
+						  buf, size, offset, f);
 	case LXC_TYPE_PROC_STAT:
-		return proc_stat_read(buf, size, offset, fi);
+		if (liblxcfs_functional())
+			return proc_stat_read(buf, size, offset, fi);
+
+		return read_file_fuse_with_offset(LXC_TYPE_PROC_STAT_PATH, buf,
+						  size, offset, f);
 	case LXC_TYPE_PROC_DISKSTATS:
-		return proc_diskstats_read(buf, size, offset, fi);
+		if (liblxcfs_functional())
+			return proc_diskstats_read(buf, size, offset, fi);
+
+		return read_file_fuse_with_offset(LXC_TYPE_PROC_DISKSTATS_PATH,
+						  buf, size, offset, f);
 	case LXC_TYPE_PROC_SWAPS:
-		return proc_swaps_read(buf, size, offset, fi);
+		if (liblxcfs_functional())
+			return proc_swaps_read(buf, size, offset, fi);
+
+		return read_file_fuse_with_offset(LXC_TYPE_PROC_SWAPS_PATH, buf,
+						  size, offset, f);
 	case LXC_TYPE_PROC_LOADAVG:
-		return proc_loadavg_read(buf, size, offset, fi);
+		if (liblxcfs_functional())
+			return proc_loadavg_read(buf, size, offset, fi);
+
+		return read_file_fuse_with_offset(LXC_TYPE_PROC_LOADAVG_PATH,
+						  buf, size, offset, f);
 	}
 
 	return -EINVAL;

diff --git a/src/sysfs_fuse.c b/src/sysfs_fuse.c
@@ -295,7 +295,11 @@ __lxcfs_fuse_ops int sys_read(const char *path, char *buf, size_t size,
 
 	switch (f->type) {
 	case LXC_TYPE_SYS_DEVICES_SYSTEM_CPU_ONLINE:
-		return sys_devices_system_cpu_online_read(buf, size, offset, fi);
+		if (liblxcfs_functional())
+			return sys_devices_system_cpu_online_read(buf, size, offset, fi);
+
+		return read_file_fuse_with_offset(LXC_TYPE_SYS_DEVICES_SYSTEM_CPU_ONLINE_PATH,
+						  buf, size, offset, f);
 	case LXC_TYPE_SYS_DEVICES:
 		break;
 	case LXC_TYPE_SYS_DEVICES_SYSTEM:

diff --git a/src/utils.c b/src/utils.c
@@ -344,9 +344,34 @@ int read_file_fuse(const char *path, char *buf, size_t size, struct file_info *d
 
 	if (d->size > total_len)
 		d->cached = d->size - total_len;
+
 	return total_len;
 }
 
+int read_file_fuse_with_offset(const char *path, char *buf, size_t size,
+			       off_t offset, struct file_info *d)
+{
+	if (offset) {
+		ssize_t total_len = 0;
+		char *cache = d->buf;
+		int left;
+
+		if (offset > d->size)
+			return -EINVAL;
+
+		if (!d->cached)
+			return 0;
+
+		left = d->size - offset;
+		total_len = left > size ? size : left;
+		memcpy(buf, cache + offset, total_len);
+
+		return total_len;
+	}
+
+	return read_file_fuse(path, buf, size, d);
+}
+
 #define INITSCOPE "/init.scope"
 void prune_init_slice(char *cg)
 {

diff --git a/src/utils.h b/src/utils.h
@@ -45,6 +45,8 @@ extern int send_creds(int sock, struct ucred *cred, char v, bool pingfirst);
 extern bool wait_for_sock(int sock, int timeout);
 extern int read_file_fuse(const char *path, char *buf, size_t size,
 			  struct file_info *d);
+extern int read_file_fuse_with_offset(const char *path, char *buf, size_t size,
+				      off_t offset, struct file_info *d);
 extern void prune_init_slice(char *cg);
 extern int wait_for_pid(pid_t pid);