klibc: patch CVE-2021-31873

Details: https://nvd.nist.gov/vuln/detail/CVE-2021-31873

Pick the patch mentioned by the nvd report.

Signed-off-by: Gyorgy Sarvari <skandigraun@gmail.com>

meta-initramfs/recipes-devtools/klibc/files/CVE-2021-31873.patch

@@ -0,0 +1,43 @@
+From 34f6170eca948ad221effc79db1f38c51e20329f Mon Sep 17 00:00:00 2001
+From: Ben Hutchings <ben@decadent.org.uk>
+Date: Wed, 28 Apr 2021 04:03:49 +0200
+Subject: [PATCH] malloc: Fail if requested size > PTRDIFF_MAX
+
+malloc() adds some overhead to the requested size, which may result in
+an integer overflow and subsequent buffer overflow if it is close to
+SIZE_MAX.  It should fail if size is large enough for this to happen.
+
+Further, it's not legal for a C object to be larger than
+PTRDIFF_MAX (half of SIZE_MAX) as pointer arithmetic within it could
+overflow.  So return failure immediately if size is greater than that.
+
+CVE-2021-31873
+
+CVE: CVE-2021-31873
+Upstream-Status: Backport [https://git.kernel.org/pub/scm/libs/klibc/klibc.git/commit/?id=a31ae8c508fc8d1bca4f57e9f9f88127572d5202]
+
+Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
+---
+ usr/klibc/malloc.c | 9 +++++++++
+ 1 file changed, 9 insertions(+)
+
+diff --git a/usr/klibc/malloc.c b/usr/klibc/malloc.c
+index 413b733..14bfa63 100644
+--- a/usr/klibc/malloc.c
++++ b/usr/klibc/malloc.c
+@@ -146,6 +146,15 @@ void *malloc(size_t size)
+ 	if (size == 0)
+ 		return NULL;
+ 
++	/* Various additions below will overflow if size is close to
++	   SIZE_MAX.  Further, it's not legal for a C object to be
++	   larger than PTRDIFF_MAX (half of SIZE_MAX) as pointer
++	   arithmetic within it could overflow. */
++	if (size > PTRDIFF_MAX) {
++		errno = ENOMEM;
++		return NULL;
++	}
++
+ 	/* Add the obligatory arena header, and round up */
+ 	size = (size + 2 * sizeof(struct arena_header) - 1) & ARENA_SIZE_MASK;
+ 

meta-initramfs/recipes-devtools/klibc/klibc.inc

@@ -24,6 +24,7 @@ SRC_URI = "${KERNELORG_MIRROR}/linux/libs/klibc/2.0/klibc-${PV}.tar.xz \
            file://CVE-2021-31870.patch \
            file://CVE-2021-31871.patch \
            file://CVE-2021-31872.patch \
+           file://CVE-2021-31873.patch \
            "
 
 ARMPATCHES ?= ""