grub: fix wrong handling of argc == 0

This change fixes wrong handling of argc == 0 causing a memory leak.
It is a part of a security series [1].

[1] https://lists.gnu.org/archive/html/grub-devel/2021-03/msg00007.html

(From OE-Core rev: 8e537ef16bc1ef4bc807cc165d3b7eb1301578de)

Signed-off-by: Marta Rybczynska <marta.rybczynska@huawei.com>
Signed-off-by: Steve Sakoman <steve@sakoman.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

meta/recipes-bsp/grub/files/0004-kern-parser-Fix-resource-leak-if-argc-0.patch

@@ -0,0 +1,50 @@
+From 8861fa6226f7229105722ba669465e879b56ee2b Mon Sep 17 00:00:00 2001
+From: Darren Kenny <darren.kenny@oracle.com>
+Date: Fri, 22 Jan 2021 12:32:41 +0000
+Subject: [PATCH] kern/parser: Fix resource leak if argc == 0
+
+After processing the command-line yet arriving at the point where we are
+setting argv, we are allocating memory, even if argc == 0, which makes
+no sense since we never put anything into the allocated argv.
+
+The solution is to simply return that we've successfully processed the
+arguments but that argc == 0, and also ensure that argv is NULL when
+we're not allocating anything in it.
+
+There are only 2 callers of this function, and both are handling a zero
+value in argc assuming nothing is allocated in argv.
+
+Fixes: CID 96680
+
+Signed-off-by: Darren Kenny <darren.kenny@oracle.com>
+Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>
+
+Upstream-Status: Backport [https://git.savannah.gnu.org/cgit/grub.git/commit/?id=d06161b035dde4769199ad65aa0a587a5920012b]
+Signed-off-by: Marta Rybczynska <marta.rybczynska@huawei.com>
+---
+ grub-core/kern/parser.c | 5 +++++
+ 1 file changed, 5 insertions(+)
+
+diff --git a/grub-core/kern/parser.c b/grub-core/kern/parser.c
+index 619db31..d1cf061 100644
+--- a/grub-core/kern/parser.c
++++ b/grub-core/kern/parser.c
+@@ -146,6 +146,7 @@ grub_parser_split_cmdline (const char *cmdline,
+   int i;
+ 
+   *argc = 0;
++  *argv = NULL;
+   do
+     {
+       if (!rd || !*rd)
+@@ -207,6 +208,10 @@ grub_parser_split_cmdline (const char *cmdline,
+       (*argc)++;
+     }
+ 
++  /* If there are no args, then we're done. */
++  if (!*argc)
++    return 0;
++
+   /* Reserve memory for the return values.  */
+   args = grub_malloc (bp - buffer);
+   if (!args)

meta/recipes-bsp/grub/grub2.inc

@@ -50,6 +50,7 @@ SRC_URI = "${GNU_MIRROR}/grub/grub-${PV}.tar.gz \
            file://0001-mmap-Fix-memory-leak-when-iterating-over-mapped-memo.patch \
            file://0002-net-net-Fix-possible-dereference-to-of-a-NULL-pointe.patch \
            file://0003-net-tftp-Fix-dangling-memory-pointer.patch \
+           file://0004-kern-parser-Fix-resource-leak-if-argc-0.patch \
            "
 SRC_URI[md5sum] = "5ce674ca6b2612d8939b9e6abed32934"
 SRC_URI[sha256sum] = "f10c85ae3e204dbaec39ae22fa3c5e99f0665417e91c2cb49b7e5031658ba6ea"