From bc1d44460cc92a734b9999042dfeef8c6be3fd9c Mon Sep 17 00:00:00 2001
From: Giuseppe Scrivano <giuseppe@scrivano.org>
Date: Thu, 24 Sep 2020 18:00:18 +0200
Subject: [PATCH] container: truncate pid file before writing it

Closes: https://github.com/containers/crun/issues/504

Signed-off-by: Giuseppe Scrivano <giuseppe@scrivano.org>
---
 src/libcrun/container.c |  4 ++--
 src/libcrun/utils.c     | 10 ++++++++--
 src/libcrun/utils.h     |  2 ++
 3 files changed, 12 insertions(+), 4 deletions(-)

diff --git a/src/libcrun/container.c b/src/libcrun/container.c
index 109f5337a0..927986a467 100644
--- a/src/libcrun/container.c
+++ b/src/libcrun/container.c
@@ -1230,7 +1230,7 @@ wait_for_process (pid_t pid, libcrun_context_t *context, int terminal_fd, int no
     {
       char buf[12];
       size_t buf_len = sprintf (buf, "%d", pid);
-      ret = write_file (context->pid_file, buf, buf_len, err);
+      ret = write_file_with_flags (context->pid_file, O_CREAT | O_TRUNC, buf, buf_len, err);
       if (UNLIKELY (ret < 0))
         return ret;
     }
@@ -2864,7 +2864,7 @@ libcrun_container_restore (libcrun_context_t *context, const char *id, libcrun_c
     {
       char buf[12];
       size_t buf_len = sprintf (buf, "%d", status.pid);
-      ret = write_file (context->pid_file, buf, buf_len, err);
+      ret = write_file_with_flags (context->pid_file, O_CREAT | O_TRUNC, buf, buf_len, err);
       if (UNLIKELY (ret < 0))
         return ret;
     }
diff --git a/src/libcrun/utils.c b/src/libcrun/utils.c
index e2d5991511..b1df0fe288 100644
--- a/src/libcrun/utils.c
+++ b/src/libcrun/utils.c
@@ -111,9 +111,9 @@ write_file_at (int dirfd, const char *name, const void *data, size_t len, libcru
 }
 
 int
-write_file (const char *name, const void *data, size_t len, libcrun_error_t *err)
+write_file_with_flags (const char *name, int flags, const void *data, size_t len, libcrun_error_t *err)
 {
-  cleanup_close int fd = open (name, O_WRONLY | O_CREAT, 0700);
+  cleanup_close int fd = open (name, O_WRONLY | flags, 0700);
   int ret;
   if (UNLIKELY (fd < 0))
     return crun_make_error (err, errno, "opening file `%s` for writing", name);
@@ -125,6 +125,12 @@ write_file (const char *name, const void *data, size_t len, libcrun_error_t *err
   return ret;
 }
 
+int
+write_file (const char *name, const void *data, size_t len, libcrun_error_t *err)
+{
+  return write_file_with_flags (name, O_CREAT, data, len, err);
+}
+
 int
 detach_process ()
 {
diff --git a/src/libcrun/utils.h b/src/libcrun/utils.h
index 8f77820e8a..178a9575b3 100644
--- a/src/libcrun/utils.h
+++ b/src/libcrun/utils.h
@@ -149,6 +149,8 @@ int xasprintf (char **str, const char *fmt, ...);
 
 int crun_path_exists (const char *path, libcrun_error_t *err);
 
+int write_file_with_flags (const char *name, int flags, const void *data, size_t len, libcrun_error_t *err);
+
 int write_file (const char *name, const void *data, size_t len, libcrun_error_t *err);
 
 int write_file_at (int dirfd, const char *name, const void *data, size_t len, libcrun_error_t *err);