[PATCH] kvmtool: don't rely on $HOME

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kvm__set_dir() called in main() and kvm__get_dir() rely on $HOME. But in
some environments (such as starting lkvm through systemd-run), $HOME is
undefined. This causes bind() to use a socket path containing "(null)"
and this fails. The current code does not check errors returned by
realpath().

Symptoms:

| bind: No such file or directory
|   Error: Failed adding socket to epoll
|  Warning: Failed init: kvm_ipc__init
|
|  Fatal: Initialisation failed

This bug was first reported on https://github.com/coreos/rkt/issues/1393

Instead of using "$HOME/.lkvm/" (i.e. "/root/.lkvm/"), this patch uses
"/var/lib/lkvm/". This also improve the error reporting by printing the
socket filename.

Signed-off-by: Alban Crequy <alban.crequy@xxxxxxxxx>
---
 include/kvm/kvm.h |  5 ++---
 kvm-ipc.c         |  1 +
 kvm.c             | 26 ++++++++------------------
 main.c            |  6 +++++-
 4 files changed, 16 insertions(+), 22 deletions(-)

diff --git a/include/kvm/kvm.h b/include/kvm/kvm.h
index 37155db..368f256 100644
--- a/include/kvm/kvm.h
+++ b/include/kvm/kvm.h
@@ -16,8 +16,7 @@
 #define SIGKVMEXIT		(SIGRTMIN + 0)
 #define SIGKVMPAUSE		(SIGRTMIN + 1)
 
-#define KVM_PID_FILE_PATH	"/.lkvm/"
-#define HOME_DIR		getenv("HOME")
+#define KVM_PID_FILE_PATH	"/var/lib/lkvm/"
 #define KVM_BINARY_NAME		"lkvm"
 
 #ifndef PAGE_SIZE
@@ -70,7 +69,7 @@ struct kvm {
 	int			vm_state;
 };
 
-void kvm__set_dir(const char *fmt, ...);
+int kvm__set_dir(void);
 const char *kvm__get_dir(void);
 
 int kvm__init(struct kvm *kvm);
diff --git a/kvm-ipc.c b/kvm-ipc.c
index 857b0dc..d94456c 100644
--- a/kvm-ipc.c
+++ b/kvm-ipc.c
@@ -60,6 +60,7 @@ static int kvm__create_socket(struct kvm *kvm)
 	r = bind(s, (struct sockaddr *)&local, len);
 	if (r < 0) {
 		perror("bind");
+		pr_err("Cannot bind on %s", full_name);
 		goto fail;
 	}
 
diff --git a/kvm.c b/kvm.c
index 10ed230..482f47b 100644
--- a/kvm.c
+++ b/kvm.c
@@ -63,31 +63,21 @@ extern struct kvm_ext kvm_req_ext[];
 
 static char kvm_dir[PATH_MAX];
 
-static int set_dir(const char *fmt, va_list args)
+int kvm__set_dir(void)
 {
-	char tmp[PATH_MAX];
+	int err;
 
-	vsnprintf(tmp, sizeof(tmp), fmt, args);
-
-	mkdir(tmp, 0777);
-
-	if (!realpath(tmp, kvm_dir))
-		return -errno;
+	err = mkdir(KVM_PID_FILE_PATH, 0700);
+	if (err != 0 && errno != EEXIST) {
+		perror("mkdir " KVM_PID_FILE_PATH);
+		return 1;
+	}
 
-	strcat(kvm_dir, "/");
+	snprintf(kvm_dir, sizeof(kvm_dir), KVM_PID_FILE_PATH);
 
 	return 0;
 }
 
-void kvm__set_dir(const char *fmt, ...)
-{
-	va_list args;
-
-	va_start(args, fmt);
-	set_dir(fmt, args);
-	va_end(args);
-}
-
 const char *kvm__get_dir(void)
 {
 	return kvm_dir;
diff --git a/main.c b/main.c
index 05bc82c..22cc4e2 100644
--- a/main.c
+++ b/main.c
@@ -13,7 +13,11 @@ static int handle_kvm_command(int argc, char **argv)
 
 int main(int argc, char *argv[])
 {
-	kvm__set_dir("%s/%s", HOME_DIR, KVM_PID_FILE_PATH);
+	int ret;
+
+	ret = kvm__set_dir();
+	if (ret != 0)
+		return ret;
 
 	return handle_kvm_command(argc - 1, &argv[1]);
 }
-- 
2.4.3

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