rootless: provide workaround for missing renameat2

on RHEL 7.7 renameat2 is not implemented for s390x, provide a workaround. Closes: https://bugzilla.redhat.com/show_bug.cgi?id=1768519 Signed-off-by: Giuseppe Scrivano <[email protected]>
mheon · Nov 6, 2019 · 0a8dcd7 · 0a8dcd7
1 parent a114e90
commit 0a8dcd7
Showing 1 changed file with 7 additions and 3 deletions.
diff --git a/pkg/rootless/rootless_linux.c b/pkg/rootless/rootless_linux.c
@@ -27,9 +27,13 @@ int renameat2 (int olddirfd, const char *oldpath, int newdirfd, const char *newp
 # ifdef SYS_renameat2
   return (int) syscall (SYS_renameat2, olddirfd, oldpath, newdirfd, newpath, flags);
 # else
-  /* no way to implement it atomically.  */
-  errno = ENOSYS;
-  return -1;
+  /* This might be an issue if another process is trying to read the file while it is empty.  */
+  int fd = open (newpath, O_EXCL|O_CREAT, 0700);
+  if (fd < 0)
+    return fd;
+  close (fd);
+  /* We are sure we created the file, let's overwrite it.  */
+  return rename (oldpath, newpath);
 # endif
 }
 #endif