From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
From: Zhongling He <zhonglingh@linux.alibaba.com>
Date: Tue, 29 Mar 2022 17:27:13 +0800
Subject: [PATCH] Fix a bug in bls_make_list, blscfg

We have encountered a bug while running LifseaOS aarch64 version without
initrd. This commit fixes this bug. It may have fixed some potential
bugs as well.

There are 4 partitions in a LifseaOS disk image:
- The 1st partition is for BIOS bootloader
- The 2nd partition is for UEFI booting, which contains grub binary
  compiled from this source code, grubaa64.efi
- The 3rd partition contains grub.cfg files and
  loader/entries/ostree-1-LifseaOS.conf
- The 4th partition contains rootfs

Since x86_64 supports both BIOS and UEFI booting and we employ BIOS
booting for x86_64 (w/o initrd) image, we don't put the grub2 binary
compiled into the 2nd partition. As a result, this bug was not observed.
However, aarch64 only supports UEFI booting. In other words, we are
using this grub2 to boot LifseaOS (w/o initrd).

grubaa64.efi from the 2nd partition will read `/grub2/grub.cfg` in the
3rd partition.

```
...
    set ignition_firstboot="ignition.firstboot
${ignition_network_kcmdline}"
fi

blscfg
```

`blscfg` is a command to convert `loader/entries/ostree-1-LifseaOS.conf`
into a typical grub.cfg. However, here comes the bug. While booting, an
error message will appear.

```
error: ../../grub-core/loader/arm64/linux.c:292:filename expected.
Press any key to continue.
```

This is because the bug in `blscfg` unexpectedly add a line, `initrd`,
into the generated grub.cfg file. Grub2 will expect an initrd file path
after `initrd`. As a result, the error occurs.

In grub-core/command/blscfg.c:676, if `initrds` is a non-NULL pointer,
then `src` will contain a `initrd` line.

```
static void create_entry (struct bls_entry *entry){
    ...
    initrds = bls_make_list (entry, "initrd", NULL); //
    ...
    if (initrds){
        ...
        tmp = grub_stpcpy(initrd, "initrd ");
        ...
    }
    ...
    src = grub_xasprintf ("load_video\n"
        "set gfx_payload=keep\n"
        "insmod gzio\n"
        "linux %s%s%s%s\n"
        "%s",
        GRUB_BOOT_DEVICE, clinux, options ? " " : "", options ? options
: "",
        initrd ? initrd : "");
```

In grub-core/command/blscfg.c:562, `bls_make_list` will always return a
non-NULL pointer except for a `grub_malloc` error.

```
static char **bls_make_list (struct bls_entry *entry, const char *key,
int *num)
{
  ...
  list = grub_malloc (sizeof (char *));
  if (!list)
    return NULL;
  list[0] = NULL;
  ...
  return list;
}
```

Therefore, `initrd` like will be appended into the auto-generated
grub.cfg if `grub_malloc` succeed, regardless of whether initrd is
stated in config file. Our bug fix, same as upstream, modifies the
behaviour of `bls_make_list`. `bls_make_list` will now return a non-NULL
pointer only if the required field actually exists.

---
 grub-core/commands/blscfg.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/grub-core/commands/blscfg.c b/grub-core/commands/blscfg.c
index 795a9f9..bf18270 100644
--- a/grub-core/commands/blscfg.c
+++ b/grub-core/commands/blscfg.c
@@ -589,6 +589,12 @@ static char **bls_make_list (struct bls_entry *entry, const char *key, int *num)
       list[nlist] = NULL;
   }
 
+  if (!nlist)
+    {
+      grub_free (list);
+      return NULL;
+    }
+
   if (num)
     *num = nlist;
 
-- 
2.27.0