fuse: dax: set fc->dax to NULL in fuse_dax_conn_free()

commit 7f8ed28d1401320bcb02dda81b3c23ab2dc5a6d8 upstream.

fuse_dax_conn_free() will be called when fuse_fill_super_common() fails
after fuse_dax_conn_alloc(). Then deactivate_locked_super() in
virtio_fs_get_tree() will call virtio_kill_sb() to release the discarded
superblock. This will call fuse_dax_conn_free() again in fuse_conn_put(),
resulting in a possible double free.

Fixes: 1dd539577c42 ("virtiofs: add a mount option to enable dax")
Signed-off-by: Hangyu Hua <hbh25y@gmail.com>
Acked-by: Vivek Goyal <vgoyal@redhat.com>
Reviewed-by: Jingbo Xu <jefflexu@linux.alibaba.com>
Cc: <stable@vger.kernel.org> # v5.10
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/fs/fuse/dax.c b/fs/fuse/dax.c
index 23904a6a9a96f74a45eb8c2f9bf72d795e05ac60..12ef91d170bb3091ac35a33d2b9dc38330b00948 100644 (file)
--- a/fs/fuse/dax.c
+++ b/fs/fuse/dax.c
@@ -1222,6 +1222,7 @@ void fuse_dax_conn_free(struct fuse_conn *fc)
        if (fc->dax) {
                fuse_free_dax_mem_ranges(&fc->dax->free_ranges);
                kfree(fc->dax);
+               fc->dax = NULL;
        }
 }