From: Sebastian Hasler <sebastian.has...@stuvus.uni-stuttgart.de>
With the current implementation, blocking flock can lead to
deadlock. Thus, it's better to return EOPNOTSUPP if a user attempts
to perform a blocking flock request.
Signed-off-by: Sebastian Hasler <sebastian.has...@stuvus.uni-stuttgart.de>
Message-Id: <20220113153249.710216-1-sebastian.has...@stuvus.uni-stuttgart.de>
Signed-off-by: Dr. David Alan Gilbert <dgilb...@redhat.com>
Reviewed-by: Vivek Goyal <vgo...@redhat.com>
Reviewed-by: Greg Kurz <gr...@kaod.org>
---
tools/virtiofsd/passthrough_ll.c | 9 +++++++++
1 file changed, 9 insertions(+)
diff --git a/tools/virtiofsd/passthrough_ll.c b/tools/virtiofsd/passthrough_ll.c
index b3d0674f6d..3e56d1cd95 100644
--- a/tools/virtiofsd/passthrough_ll.c
+++ b/tools/virtiofsd/passthrough_ll.c
@@ -2467,6 +2467,15 @@ static void lo_flock(fuse_req_t req, fuse_ino_t ino,
struct fuse_file_info *fi,
int res;
(void)ino;
+ if (!(op & LOCK_NB)) {
+ /*
+ * Blocking flock can deadlock as there is only one thread
+ * serving the queue.
+ */
+ fuse_reply_err(req, EOPNOTSUPP);
+ return;
+ }
+
res = flock(lo_fi_fd(req, fi), op);
fuse_reply_err(req, res == -1 ? errno : 0);
--
2.35.1
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