glibc: Fix CVE-2023-4911 "Looney Tunables"

Take the patch from the source for Debian's glibc 2.31-13+deb11u7
package, the changelog for which starts with:

 glibc (2.31-13+deb11u7) bullseye-security; urgency=medium

   * debian/patches/any/local-CVE-2023-4911.patch: Fix a buffer overflow in the
     dynamic loader's processing of the GLIBC_TUNABLES environment variable
     (CVE-2023-4911).

This addresses the "Looney Tunables" vulnerability described at
https://www.qualys.com/2023/10/03/cve-2023-4911/looney-tunables-local-privilege-escalation-glibc-ld-so.txt

(From OE-Core rev: 9a800a2e2c2b14eab8c1f83cb4ac3b94a70dd23c)

Signed-off-by: Mike Crowe <mac@mcrowe.com>
Signed-off-by: Steve Sakoman <steve@sakoman.com>

meta/recipes-core/glibc/glibc/CVE-2023-4911.patch

@@ -0,0 +1,63 @@
+From d2b77337f734fcacdfc8e0ddec14cf31a746c7be Mon Sep 17 00:00:00 2001
+From: Siddhesh Poyarekar <siddhesh@redhat.com>
+Date: Mon, 11 Sep 2023 18:53:15 -0400
+Subject: [PATCH v2] tunables: Terminate immediately if end of input is reached
+
+The string parsing routine may end up writing beyond bounds of tunestr
+if the input tunable string is malformed, of the form name=name=val.
+This gets processed twice, first as name=name=val and next as name=val,
+resulting in tunestr being name=name=val:name=val, thus overflowing
+tunestr.
+
+Terminate the parsing loop at the first instance itself so that tunestr
+does not overflow.
+---
+Changes from v1:
+
+- Also null-terminate tunestr before exiting.
+
+ elf/dl-tunables.c | 17 ++++++++++-------
+ 1 file changed, 10 insertions(+), 7 deletions(-)
+
+Upstream-Status: Backport [git://sourceware.org/git/glibc.git]
+CVE: CVE-2023-4911
+
+diff --git a/elf/dl-tunables.c b/elf/dl-tunables.c
+index 8e7ee9df10..76cf8b9da3 100644
+--- a/elf/dl-tunables.c
++++ b/elf/dl-tunables.c
+@@ -187,11 +187,7 @@ parse_tunables (char *tunestr, char *valstring)
+       /* If we reach the end of the string before getting a valid name-value
+ 	 pair, bail out.  */
+       if (p[len] == '\0')
+-	{
+-	  if (__libc_enable_secure)
+-	    tunestr[off] = '\0';
+-	  return;
+-	}
++	break;
+ 
+       /* We did not find a valid name-value pair before encountering the
+ 	 colon.  */
+@@ -251,9 +247,16 @@ parse_tunables (char *tunestr, char *valstring)
+ 	    }
+ 	}
+ 
+-      if (p[len] != '\0')
+-	p += len + 1;
++      /* We reached the end while processing the tunable string.  */
++      if (p[len] == '\0')
++	break;
++
++      p += len + 1;
+     }
++
++  /* Terminate tunestr before we leave.  */
++  if (__libc_enable_secure)
++    tunestr[off] = '\0';
+ }
+ #endif
+ 
+-- 
+2.41.0
+

meta/recipes-core/glibc/glibc_2.31.bb

@@ -80,6 +80,7 @@ SRC_URI =  "${GLIBC_GIT_URI};branch=${SRCBRANCH};name=glibc \
            file://0036-i386-Avoid-lazy-relocation-of-tlsdesc-BZ-27137.patch \
            file://0037-Avoid-deadlock-between-pthread_create-and-ctors.patch \
            file://CVE-2023-0687.patch \
+           file://CVE-2023-4911.patch \
            "
 S = "${WORKDIR}/git"
 B = "${WORKDIR}/build-${TARGET_SYS}"