fuse: do not allow mapping a non-regular backing file

We do not support passthrough operations other than read/write on
regular file, so allowing non-regular backing files makes no sense.

Fixes: efad7153bf93 ("fuse: allow O_PATH fd for FUSE_DEV_IOC_BACKING_OPEN")
Cc: stable@vger.kernel.org
Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Reviewed-by: Bernd Schubert <bschubert@ddn.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>

diff --git a/fs/fuse/passthrough.c b/fs/fuse/passthrough.c
index 607ef735ad4ab387c2b431eb989f4319dd65d7a6..eb97ac009e75d97f0cabb0652b65a21ddaa913ad 100644 (file)
--- a/fs/fuse/passthrough.c
+++ b/fs/fuse/passthrough.c
@@ -237,6 +237,11 @@ int fuse_backing_open(struct fuse_conn *fc, struct fuse_backing_map *map)
        if (!file)
                goto out;
 
+       /* read/write/splice/mmap passthrough only relevant for regular files */
+       res = d_is_dir(file->f_path.dentry) ? -EISDIR : -EINVAL;
+       if (!d_is_reg(file->f_path.dentry))
+               goto out_fput;
+
        backing_sb = file_inode(file)->i_sb;
        res = -ELOOP;
        if (backing_sb->s_stack_depth >= fc->max_stack_depth)