From 6868ca795390aeee525210e017bd03f57147e0f7 Mon Sep 17 00:00:00 2001
From: John Reiser <jreiser@BitWagon.com>
Date: Wed, 15 Apr 2020 13:29:01 -0700
Subject: [PATCH] getElfSections concentrates on _Shdr[.e_shstrndx]

https://github.com/upx/upx/issues/363
	modified:   p_vmlinx.cpp
---
 src/p_vmlinx.cpp | 54 ++++++++++++++++++++++--------------------------
 1 file changed, 25 insertions(+), 29 deletions(-)

diff --git a/src/p_vmlinx.cpp b/src/p_vmlinx.cpp
index c8f9a9d0..c6a8f5c1 100644
--- a/src/p_vmlinx.cpp
+++ b/src/p_vmlinx.cpp
@@ -104,42 +104,38 @@ PackVmlinuxBase<T>::compare_Phdr(void const *aa, void const *bb)
 template <class T>
 typename T::Shdr const *PackVmlinuxBase<T>::getElfSections()
 {
-    Shdr const *p, *shstrsec=0;
+    Shdr const *p;
+    unsigned const e_shnum = ehdri.e_shnum;
     if (ehdri.e_shentsize != sizeof(*shdri)
     ||  (unsigned long)file_size < ehdri.e_shoff
-    ||  (unsigned long)file_size < ehdri.e_shoff + ehdri.e_shentsize * ehdri.e_shnum) {
+    ||  (unsigned long)file_size < ehdri.e_shoff + ehdri.e_shentsize * e_shnum) {
         throwCantPack("bad ElfXX_Shdrs");
     }
-    shdri = new Shdr[(unsigned) ehdri.e_shnum];
+    shdri = new Shdr[(unsigned) e_shnum];
     fi->seek(ehdri.e_shoff, SEEK_SET);
-    fi->readx(shdri, ehdri.e_shnum * sizeof(*shdri));
-    unsigned e_shnum = ehdri.e_shnum;
-    unsigned j;
-    for (p = shdri, j = 0; j < e_shnum; ++j, ++p) {
-        if (Shdr::SHT_STRTAB==p->sh_type
-        &&  p->sh_offset  <= ((unsigned long)file_size - sizeof(*shdri))
-        &&  p->sh_size    <= ((unsigned long)file_size - p->sh_offset)
-        &&  p->sh_name    <= ((unsigned long)file_size - p->sh_offset)
-        &&  10            <= ((unsigned long)file_size - p->sh_name)
-            // 10 == (1+ strlen(".shstrtab"))
-        ) {
-            if (p->sh_size <= p->sh_name) {
-                char msg[50]; snprintf(msg, sizeof(msg),
-                    "bad SHT_STRTAB[%u]", j);
-                throwCantPack(msg);
-            }
-            delete [] shstrtab;
-            shstrtab = new char[1+ p->sh_size];
-            fi->seek(p->sh_offset, SEEK_SET);
-            fi->readx(shstrtab, p->sh_size);
-            shstrtab[p->sh_size] = '\0';
-            if (0==strcmp(".shstrtab", shstrtab + p->sh_name)) {
-                shstrsec = p;
-                break;
-            }
+    fi->readx(shdri, e_shnum * sizeof(*shdri));
+    p = &shdri[ehdri.e_shstrndx];  // supposed
+    if (Shdr::SHT_STRTAB==p->sh_type
+    &&  p->sh_offset  <= ((unsigned long)file_size - sizeof(*shdri))
+    &&  p->sh_size    <= ((unsigned long)file_size - p->sh_offset)
+    &&  p->sh_name    <= ((unsigned long)file_size - p->sh_offset)
+    &&  10            <= ((unsigned long)file_size - p->sh_name)
+        // 10 == (1+ strlen(".shstrtab"))
+    ) {
+        if (p->sh_size <= p->sh_name) {
+            char msg[50]; snprintf(msg, sizeof(msg),
+                "bad .shstrtab _Shdr[%u]", (unsigned)ehdri.e_shstrndx);
+            throwCantPack(msg);
+        }
+        shstrtab = new char[1+ p->sh_size];
+        fi->seek(p->sh_offset, SEEK_SET);
+        fi->readx(shstrtab, p->sh_size);
+        shstrtab[p->sh_size] = '\0';
+        if (0==strcmp(".shstrtab", shstrtab + p->sh_name)) {
+            return p;
         }
     }
-    return shstrsec;
+    return 0;
 }
 
 template <class T>