On Thu, 13 Jun 2024 at 03:32, Youzhong Yang <youzhong@xxxxxxxxx> wrote: > I analyzed the crash dump, here is what I figured out: > - The overlay fs is mounted with only 2 lowerdirs, and nfs_export=on > - When ovl_dentry_to_fid() is called on the root dentry: > - ovl_check_encode_origin(dentry) returns 0 as euc_lower (I believe > it should return 1 in this case) > - "enc_lower ? ovl_dentry_lower(dentry) : ovl_dentry_upper(dentry)" > evaluates to NULL > - NULL is passed as the second argument to ovl_encode_real_fh(), so > it crashes Thank you for the excellent report. The attached patch (untested) should fix it. Thanks, Miklos
--- fs/overlayfs/export.c | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-) --- a/fs/overlayfs/export.c +++ b/fs/overlayfs/export.c @@ -181,6 +181,10 @@ static int ovl_check_encode_origin(struc struct ovl_fs *ofs = OVL_FS(dentry->d_sb); bool decodable = ofs->config.nfs_export; + /* No upper layer? */ + if (!ovl_upper_mnt(ofs)) + return 1; + /* Lower file handle for non-upper non-decodable */ if (!ovl_dentry_upper(dentry) && !decodable) return 1; @@ -209,7 +213,7 @@ static int ovl_check_encode_origin(struc * ovl_connect_layer() will try to make origin's layer "connected" by * copying up a "connectable" ancestor. */ - if (d_is_dir(dentry) && ovl_upper_mnt(ofs) && decodable) + if (d_is_dir(dentry) && decodable) return ovl_connect_layer(dentry); /* Lower file handle for indexed and non-upper dir/non-dir */
