Merge tag 'block-pull-request' of https://gitlab.com/stefanha/qemu into staging

Pull request

Fix for an fd leak in the blkio block driver.

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# gpg: Signature made Thu 03 Aug 2023 08:55:41 AM PDT
# gpg:                using RSA key 8695A8BFD3F97CDAAC35775A9CA4ABB381AB73C8
# gpg: Good signature from "Stefan Hajnoczi <stefanha@redhat.com>" [full]
# gpg:                 aka "Stefan Hajnoczi <stefanha@gmail.com>" [full]

* tag 'block-pull-request' of https://gitlab.com/stefanha/qemu:
  block/blkio: add more comments on the fd passing handling
  block/blkio: close the fd when blkio_connect() fails

Signed-off-by: Richard Henderson <richard.henderson@linaro.org>

1 files changed, 20 insertions, 6 deletions

diff --git a/block/blkio.c b/block/blkio.c
index 8e7ce42..1dd4956 100644
--- a/block/blkio.c
+++ b/block/blkio.c
@@ -678,7 +678,7 @@ static int blkio_virtio_blk_connect(BlockDriverState *bs, QDict *options,
     const char *path = qdict_get_try_str(options, "path");
     BDRVBlkioState *s = bs->opaque;
     bool fd_supported = false;
-    int fd, ret;
+    int fd = -1, ret;
 
     if (!path) {
         error_setg(errp, "missing 'path' option");
@@ -713,12 +713,19 @@ static int blkio_virtio_blk_connect(BlockDriverState *bs, QDict *options,
          */
         fd = qemu_open(path, O_RDWR, NULL);
         if (fd < 0) {
+            /*
+             * qemu_open() can fail if the user specifies a path that is not
+             * a file or device, for example in the case of Unix Domain Socket
+             * for the virtio-blk-vhost-user driver. In such cases let's have
+             * libblkio open the path directly.
+             */
             fd_supported = false;
         } else {
             ret = blkio_set_int(s->blkio, "fd", fd);
             if (ret < 0) {
                 fd_supported = false;
                 qemu_close(fd);
+                fd = -1;
             }
         }
     }
@@ -733,14 +740,21 @@ static int blkio_virtio_blk_connect(BlockDriverState *bs, QDict *options,
     }
 
     ret = blkio_connect(s->blkio);
+    if (ret < 0 && fd >= 0) {
+        /* Failed to give the FD to libblkio, close it */
+        qemu_close(fd);
+        fd = -1;
+    }
+
     /*
-     * If the libblkio driver doesn't support the `fd` property, blkio_connect()
-     * will fail with -EINVAL. So let's try calling blkio_connect() again by
-     * directly setting `path`.
+     * Before https://gitlab.com/libblkio/libblkio/-/merge_requests/208
+     * (libblkio <= v1.3.0), setting the `fd` property is not enough to check
+     * whether the driver supports the `fd` property or not. In that case,
+     * blkio_connect() will fail with -EINVAL.
+     * So let's try calling blkio_connect() again by directly setting `path`
+     * to cover this scenario.
      */
     if (fd_supported && ret == -EINVAL) {
-        qemu_close(fd);
-
         /*
          * We need to clear the `fd` property we set previously by setting
          * it to -1.