From: Stefan Hajnoczi <stefanha@redhat.com>

Date: Mon, 27 Jan 2020 19:02:06 +0000

Subject: [PATCH] virtiofsd: make lo_release() atomic

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Hold the lock across both lo_map_get() and lo_map_remove() to prevent

races between two FUSE_RELEASE requests.  In this case I don't see a

serious bug but it's safer to do things atomically.

Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>

Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>

Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>

(cherry picked from commit baed65c060c0e524530bc243eec427fb408bd477)

---

 tools/virtiofsd/passthrough_ll.c | 12 ++++++++----

 1 file changed, 8 insertions(+), 4 deletions(-)

diff --git a/tools/virtiofsd/passthrough_ll.c b/tools/virtiofsd/passthrough_ll.c

index 9414935b52..690edbc4c5 100644

--- a/tools/virtiofsd/passthrough_ll.c

+++ b/tools/virtiofsd/passthrough_ll.c

@@ -1772,14 +1772,18 @@ static void lo_release(fuse_req_t req, fuse_ino_t ino,

                        struct fuse_file_info *fi)

 {

     struct lo_data *lo = lo_data(req);

-    int fd;

+    struct lo_map_elem *elem;

+    int fd = -1;

     (void)ino;

-    fd = lo_fi_fd(req, fi);

-

     pthread_mutex_lock(&lo->mutex);

-    lo_map_remove(&lo->fd_map, fi->fh);

+    elem = lo_map_get(&lo->fd_map, fi->fh);

+    if (elem) {

+        fd = elem->fd;

+        elem = NULL;

+        lo_map_remove(&lo->fd_map, fi->fh);

+    }

     pthread_mutex_unlock(&lo->mutex);

     close(fd);