From 5f5f298a4a071abf8f1d3b066c39d050ee1a03a7 Mon Sep 17 00:00:00 2001
From: Oran Agra <oran@redislabs.com>
Date: Sun, 7 Jan 2024 12:32:44 +0200
Subject: [PATCH] Fix possible corruption in sdsResize (CVE-2023-41056)

#11766 introduced a bug in sdsResize where it could forget to update
the sds type in the sds header and then cause an overflow in sdsalloc.
it looks like the only implication of that is a possible assertion in HLL,
but it's hard to rule out possible heap corruption issues with clientsCronResizeQueryBuffer
---
 src/sds.c | 28 +++++++++++++++-------------
 1 file changed, 15 insertions(+), 13 deletions(-)

diff --git a/src/sds.c b/src/sds.c
index e383e3caa..2cc5b2316 100644
--- a/src/sds.c
+++ b/src/sds.c
@@ -349,20 +349,22 @@ sds sdsResize(sds s, size_t size, int would_regrow) {
      * type. */
     int use_realloc = (oldtype==type || (type < oldtype && type > SDS_TYPE_8));
     size_t newlen = use_realloc ? oldhdrlen+size+1 : hdrlen+size+1;
-    int alloc_already_optimal = 0;
-    #if defined(USE_JEMALLOC)
-        /* je_nallocx returns the expected allocation size for the newlen.
-         * We aim to avoid calling realloc() when using Jemalloc if there is no
-         * change in the allocation size, as it incurs a cost even if the
-         * allocation size stays the same. */
-        alloc_already_optimal = (je_nallocx(newlen, 0) == zmalloc_size(sh));
-    #endif
 
-    if (use_realloc && !alloc_already_optimal) {
-        newsh = s_realloc(sh, newlen);
-        if (newsh == NULL) return NULL;
-        s = (char*)newsh+oldhdrlen;
-    } else if (!alloc_already_optimal) {
+    if (use_realloc) {
+        int alloc_already_optimal = 0;
+        #if defined(USE_JEMALLOC)
+            /* je_nallocx returns the expected allocation size for the newlen.
+             * We aim to avoid calling realloc() when using Jemalloc if there is no
+             * change in the allocation size, as it incurs a cost even if the
+             * allocation size stays the same. */
+            alloc_already_optimal = (je_nallocx(newlen, 0) == zmalloc_size(sh));
+        #endif
+        if (!alloc_already_optimal) {
+            newsh = s_realloc(sh, newlen);
+            if (newsh == NULL) return NULL;
+            s = (char*)newsh+oldhdrlen;
+        }
+    } else {
         newsh = s_malloc(newlen);
         if (newsh == NULL) return NULL;
         memcpy((char*)newsh+hdrlen, s, len);