From 0bf7060a966f91ed6251386bb6281648e416a03a Mon Sep 17 00:00:00 2001
From: j4nn <531585+j4nn@users.noreply.github.com>
Date: Sat, 17 Jan 2026 22:29:02 +0100
Subject: [PATCH] fix segfault bug that could happen in rare fail code path of
 test5

Thread 1 "xperable" received signal SIGSEGV, Segmentation fault.
0x0814d191 in memcpy ()
---
 xperable.c | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/xperable.c b/xperable.c
index c46f2f7..ca6ac02 100644
--- a/xperable.c
+++ b/xperable.c
@@ -531,9 +531,11 @@ static int test5(struct fbusb *dev, int size, int offset, const char *fname)
     if (res != FASTBOOT_DATA) {
         if (*(uint32_t *)rxbuff != 0)
             return -1;
-        i -= 4;
-        memmove(rxbuff, rxbuff + 4, i);
-        memset(rxbuff + i, 0, 4);
+        if (i > 4) {
+            i -= 4;
+            memmove(rxbuff, rxbuff + 4, i);
+            memset(rxbuff + i, 0, 4);
+        }
     }
     size = 0;
     addr = 0;