fix musl's CVE-2025-26519

Author: pietroalbini

src/ci/docker/scripts/musl.sh

@@ -31,8 +31,49 @@ MUSL=musl-1.2.3
 if [ ! -d $MUSL ]; then
   curl https://www.musl-libc.org/releases/$MUSL.tar.gz | tar xzf -
 fi
-
 cd $MUSL
+
+# Apply patches for CVE-2025-26519. At the time of adding these patches no release containing them
+# has been published by the musl project, so we just apply them directly on top of the version we
+# were distributing already. The patches should be removed once we upgrade to musl >= 1.2.6.
+#
+# Advisory: https://www.openwall.com/lists/musl/2025/02/13/1
+#
+# Patches applied:
+# - https://www.openwall.com/lists/musl/2025/02/13/1/1
+# - https://www.openwall.com/lists/musl/2025/02/13/1/2
+#
+# ignore-tidy-tab
+# ignore-tidy-linelength
+patch -p1 <<EOF
+--- a/src/locale/iconv.c
++++ b/src/locale/iconv.c
+@@ -502,7 +502,7 @@ size_t iconv(iconv_t cd, char **restrict in, size_t *restrict inb, char **restri
+ 			if (c >= 93 || d >= 94) {
+ 				c += (0xa1-0x81);
+ 				d += 0xa1;
+-				if (c >= 93 || c>=0xc6-0x81 && d>0x52)
++				if (c > 0xc6-0x81 || c==0xc6-0x81 && d>0x52)
+ 					goto ilseq;
+ 				if (d-'A'<26) d = d-'A';
+ 				else if (d-'a'<26) d = d-'a'+26;
+EOF
+patch -p1 <<EOF
+--- a/src/locale/iconv.c
++++ b/src/locale/iconv.c
+@@ -545,6 +545,10 @@ size_t iconv(iconv_t cd, char **restrict in, size_t *restrict inb, char **restri
+ 				if (*outb < k) goto toobig;
+ 				memcpy(*out, tmp, k);
+ 			} else k = wctomb_utf8(*out, c);
++			/* This failure condition should be unreachable, but
++			 * is included to prevent decoder bugs from translating
++			 * into advancement outside the output buffer range. */
++			if (k>4) goto ilseq;
+ 			*out += k;
+ 			*outb -= k;
+ 			break;
+EOF
+
 ./configure --enable-debug --disable-shared --prefix=/musl-$TAG "$@"
 if [ "$TAG" = "i586" -o "$TAG" = "i686" ]; then
   hide_output make -j$(nproc) AR=ar RANLIB=ranlib