Keep original flags for create in SafeHardlinks.

When open(2) is used with flags O_CREAT|O_RDWR, the file descriptor
must be readable. Unfortunately O_RDWR was not passed which made
read fail with EBADF and mmap to signal SIGBUS.

This issue happened with man-db for example.

Fixes #143.

2 files changed, 7 insertions, 3 deletions

diff --git a/buildstream/_fuse/fuse.py b/buildstream/_fuse/fuse.py
index 58febcba0..4ff6b9903 100644
--- a/buildstream/_fuse/fuse.py
+++ b/buildstream/_fuse/fuse.py
@@ -757,7 +757,11 @@ class FUSE(object):
         if self.raw_fi:
             return self.operations('create', path, mode, fi)
         else:
-            fi.fh = self.operations('create', path, mode)
+            # This line is different from upstream to fix issues
+            # reading file opened with O_CREAT|O_RDWR.
+            # See issue #143.
+            fi.fh = self.operations('create', path, mode, fi.flags)
+            # END OF MODIFICATION
             return 0
 
     def ftruncate(self, path, length, fip):
diff --git a/buildstream/_fuse/hardlinks.py b/buildstream/_fuse/hardlinks.py
index 4da51bb22..1386f14cf 100644
--- a/buildstream/_fuse/hardlinks.py
+++ b/buildstream/_fuse/hardlinks.py
@@ -185,12 +185,12 @@ class SafeHardlinkOps(Operations):
 
         return os.open(full_path, flags)
 
-    def create(self, path, mode, fi=None):
+    def create(self, path, mode, flags):
         full_path = self._full_path(path)
 
         # If it already exists, ensure it's a copy first
         self._ensure_copy(full_path)
-        return os.open(full_path, os.O_WRONLY | os.O_CREAT, mode)
+        return os.open(full_path, flags, mode)
 
     def read(self, path, length, offset, fh):
         os.lseek(fh, offset, os.SEEK_SET)