From 0287c6b14c77eeb3e3c61996330850d43d937a2b Mon Sep 17 00:00:00 2001 From: Jonathan Davies Date: Thu, 22 Feb 2024 16:24:01 +0000 Subject: [PATCH] shim: don't set second_stage to the empty string When LoadOptions is either L" " or L"shim.efi ", parse_load_options sets second_stage to the empty string. This is unlikely to be what is intended, and typically leads to a non-obvious failure mode. The failure happens because parse_load_options's call to split_load_options (after eating shim's own filename, if present) returns the empty string. Since init_grub typically passes second_stage to start_image, this causes read_image to concatenate the empty string onto the directory name. This means PathName refers to the directory, not the path to a pe image. Then load_image successfully opens a handle on the directory and reads "data" from it. It only eventually fails when handle_image calls read_header which finds that this data isn't in fact a pe header, reporting "Invalid image". This scenario has been seen when shim is loaded via rEFInd 0.11.5, which sets LoadOptions to the name of the shim program followed by a space character. Instead, modify parse_load_options to leave second_stage set to its default value rather than the empty string. Signed-off-by: Jonathan Davies --- load-options.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) diff --git a/load-options.c b/load-options.c index a8c6e1a3d..8b92e37f9 100644 --- a/load-options.c +++ b/load-options.c @@ -447,10 +447,12 @@ parse_load_options(EFI_LOADED_IMAGE *li) /* * Set up the name of the alternative loader and the LoadOptions for - * the loader + * the loader if it's not the empty string. */ if (loader_str) { - second_stage = loader_str; + if (*loader_str) { + second_stage = loader_str; + } load_options = remaining; load_options_size = remaining_size; }