From 41af4459ac47e107093c3f54b6875d54723aa613 Mon Sep 17 00:00:00 2001 From: Sebastian Hasler Date: Thu, 13 Jan 2022 16:32:49 +0100 Subject: [PATCH 2/2] virtiofsd: Do not support blocking flock 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 Message-Id: <20220113153249.710216-1-sebastian.hasler@stuvus.uni-stuttgart.de> Signed-off-by: Dr. David Alan Gilbert Reviewed-by: Vivek Goyal Reviewed-by: Greg Kurz --- 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