[OE-core][wrynose][PATCH v2 07/10] expat: fix CVE-2026-56409

["Deepak Rathore -X (deeratho - E INFOCHIPS PRIVATE LIMITED at Cisco)" <deeratho@cisco.com>]

From: Deepak Rathore <deeratho@cisco.com>

This patch applies the upstream fix shown in [1] as referenced by [2].

[1] https://github.com/libexpat/libexpat/commit/61f7cdda22546c4bee38dd2d3fa3d6e4aa64d33e
[2] https://nvd.nist.gov/vuln/detail/CVE-2026-56409

Signed-off-by: Deepak Rathore <deeratho@cisco.com>
---
- Changes from v1 to v2: Refresh the patch on top of
latest wrynose branch merged commits.
 .../expat/expat/CVE-2026-56409.patch          | 53 +++++++++++++++++++
 meta/recipes-core/expat/expat_2.7.5.bb        |  1 +
 2 files changed, 54 insertions(+)
 create mode 100644 meta/recipes-core/expat/expat/CVE-2026-56409.patch

diff --git a/meta/recipes-core/expat/expat/CVE-2026-56409.patch b/meta/recipes-core/expat/expat/CVE-2026-56409.patch
new file mode 100644
index 0000000000..ff0e650a2a
--- /dev/null
+++ b/meta/recipes-core/expat/expat/CVE-2026-56409.patch
@@ -0,0 +1,53 @@
+From 10938bc2cef7573087566b5b1c948061baa68b98 Mon Sep 17 00:00:00 2001
+From: netliomax25-code <netliomax25@gmail.com>
+Date: Mon, 1 Jun 2026 11:53:19 +0530
+Subject: [PATCH] xmlwf: protect output path join from integer overflow
+
+CVE: CVE-2026-56409
+Upstream-Status: Backport [https://github.com/libexpat/libexpat/commit/61f7cdda22546c4bee38dd2d3fa3d6e4aa64d33e]
+
+Backport Changes:
+- Adapt the allocation hunk to the explicit cast used by Expat 2.7.5.
+
+(cherry picked from commit 61f7cdda22546c4bee38dd2d3fa3d6e4aa64d33e)
+Signed-off-by: Deepak Rathore <deeratho@cisco.com>
+---
+ expat/xmlwf/xmlwf.c | 22 ++++++++++++++++++++--
+ 1 file changed, 20 insertions(+), 2 deletions(-)
+
+diff --git a/expat/xmlwf/xmlwf.c b/expat/xmlwf/xmlwf.c
+index 06416454..6a0a707a 100644
+--- a/expat/xmlwf/xmlwf.c
++++ b/expat/xmlwf/xmlwf.c
+@@ -1236,8 +1236,26 @@ tmain(int argc, XML_Char **argv) {
+         }
+ #endif
+       }
+-      outName = (XML_Char *)malloc((tcslen(outputDir) + tcslen(file) + 2)
+-                                   * sizeof(XML_Char));
++      const size_t outputDirLen = tcslen(outputDir);
++      const size_t fileLen = tcslen(file);
++
++      /* Detect and prevent integer overflow in the addition (without
++         risking underflow) and the multiplication, mirroring the guards
++         in xcsdup() and resolveSystemId() */
++      if (outputDirLen > SIZE_MAX - fileLen
++          || outputDirLen > SIZE_MAX - fileLen - 2) {
++        tperror(T("Could not allocate memory"));
++        exit(XMLWF_EXIT_INTERNAL_ERROR);
++      }
++
++      const size_t charsRequired = outputDirLen + fileLen + 2;
++
++      if (charsRequired > SIZE_MAX / sizeof(XML_Char)) {
++        tperror(T("Could not allocate memory"));
++        exit(XMLWF_EXIT_INTERNAL_ERROR);
++      }
++
++      outName = malloc(charsRequired * sizeof(XML_Char));
+       if (! outName) {
+         tperror(T("Could not allocate memory"));
+         exit(XMLWF_EXIT_INTERNAL_ERROR);
+-- 
+2.43.7
+
diff --git a/meta/recipes-core/expat/expat_2.7.5.bb b/meta/recipes-core/expat/expat_2.7.5.bb
index f14e39c00b..cb8f9dd1ac 100644
--- a/meta/recipes-core/expat/expat_2.7.5.bb
+++ b/meta/recipes-core/expat/expat_2.7.5.bb
@@ -28,6 +28,7 @@ SRC_URI = "${GITHUB_BASE_URI}/download/R_${VERSION_TAG}/expat-${PV}.tar.bz2  \
            file://CVE-2026-56410_p2.patch;striplevel=2 \
            file://CVE-2026-56406-dependent.patch;striplevel=2 \
            file://CVE-2026-56406.patch;striplevel=2 \
+           file://CVE-2026-56409.patch;striplevel=2 \
            "
 
 GITHUB_BASE_URI = "https://github.com/libexpat/libexpat/releases/"
-- 
2.35.6