Add one extra page to avoid overlapping with next page if its rounded down

Author: brenoguim

src/patchelf.cc

@@ -985,7 +985,9 @@ void ElfFile<ElfFileParamNames>::rewriteSectionsExecutable()
 
         /* Calculate how many bytes are needed out of the additional pages. */
         size_t extraSpace = neededSpace - startOffset; 
-        unsigned int neededPages = roundUp(extraSpace, getPageSize()) / getPageSize();
+        // Always give one extra page to avoid colliding with segments that start at
+        // unaligned addresses and will be rounded down when loaded
+        unsigned int neededPages = 1 + roundUp(extraSpace, getPageSize()) / getPageSize();
         debug("needed pages is %d\n", neededPages);
         if (neededPages * getPageSize() > firstPage)
             error("virtual address space underrun!");

tests/Makefile.am

@@ -47,14 +47,16 @@ src_TESTS = \
   print-execstack.sh \
   modify-execstack.sh \
   rename-dynamic-symbols.sh \
+  overlapping-segments-after-rounding.sh \
   empty-note.sh
 
 build_TESTS = \
   $(no_rpath_arch_TESTS)
 
 TESTS = $(src_TESTS) $(build_TESTS)
 
-EXTRA_DIST = no-rpath-prebuild $(src_TESTS) no-rpath-prebuild.sh invalid-elf endianness empty-note
+EXTRA_DIST = no-rpath-prebuild $(src_TESTS) no-rpath-prebuild.sh invalid-elf endianness empty-note \
+			 overlapping-segments-after-rounding
 
 TESTS_ENVIRONMENT = PATCHELF_DEBUG=1 STRIP=$(STRIP) OBJDUMP=$(OBJDUMP) READELF=$(READELF) OBJCOPY=$(OBJCOPY)
 

tests/overlapping-segments-after-rounding

@@ -0,0 +1,23 @@
+#! /bin/sh -e
+
+PATCHELF=$(readlink -f "../src/patchelf")
+SCRATCH="scratch/$(basename "$0" .sh)"
+READELF=${READELF:-readelf}
+
+EXEC_NAME="overlapping-segments-after-rounding"
+
+if test "$(uname -i)" = x86_64 && test "$(uname)" = Linux; then
+    rm -rf "${SCRATCH}"
+    mkdir -p "${SCRATCH}"
+
+    cp "${srcdir}/${EXEC_NAME}" "${SCRATCH}/"
+    cd "${SCRATCH}"
+
+    ${PATCHELF} --force-rpath --remove-rpath --output modified1 "${EXEC_NAME}"
+
+    ldd modified1
+
+    ${PATCHELF} --force-rpath --set-rpath "xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx" --output modified2 modified1
+
+    ldd modified2
+fi