RFR: 8330615: avoid signed integer overflows in zip_util.c readCen / hashN

[Lutz Schmidt]

On Tue, 23 Apr 2024 07:51:28 GMT, Matthias Baesken <mbaesken at openjdk.org> wrote:

> In the hashN usages of readCen from zip_util.c we see a lot of signed integer overflows.
> For example in the java/util jtreg tests those are easily reproducable when compiling with -ftrapv (clang/gcc toolchains).
> While those overflows never seem to cause crashes or similar errors, they are unwanted because
> signed integer overflows in C cause undefined behavior.
> See
> https://www.gnu.org/software/c-intro-and-ref/manual/html_node/Signed-Overflow.html
>>
>> For signed integers, the result of overflow in C is in principle undefined, meaning that anything whatsoever could happen.
>> Therefore, C compilers can do optimizations that treat the overflow case with total unconcern.
> 
> So we might still get unwanted results (maybe bad/strange hashing, depending on compiler and optimization level).
> 
> Compilation with -ftrapv causes/triggers this SIGILL on macOS showing the issue :
> # Problematic frame:
> # C [libzip.dylib+0x6362] hashN+0x32
> #
> 
> Stack: [0x000070000c496000,0x000070000c596000], sp=0x000070000c5957e0, free space=1021k
> Native frames: (J=compiled Java code, j=interpreted, Vv=VM code, C=native code)
> C [libzip.dylib+0x6362] hashN+0x32
> C [libzip.dylib+0x5d5e] readCEN+0xd2e
> C [libzip.dylib+0x4ee0] ZIP_Put_In_Cache0+0x160
> V [libjvm.dylib+0x544b1e] ClassLoader::open_zip_file(char const*, char**, JavaThread*)+0x3e
> V [libjvm.dylib+0x543fec] ClassLoader::create_class_path_entry(JavaThread*, char const*, stat const*, bool, bool)+0x6c
> V [libjvm.dylib+0x543833] ClassLoader::setup_bootstrap_search_path_impl(JavaThread*, char const*)+0xf3
> V [libjvm.dylib+0x54819b] classLoader_init1()+0x1b
> V [libjvm.dylib+0x92602a] init_globals()+0x3a
> V [libjvm.dylib+0x12b3b74] Threads::create_vm(JavaVMInitArgs*, bool*)+0x314
> V [libjvm.dylib+0xa848f4] JNI_CreateJavaVM+0x64
> C [libjli.dylib+0x4483] JavaMain+0x123
> C [libjli.dylib+0x7529] ThreadJavaMain+0x9
> C [libsystem_pthread.dylib+0x68fc] _pthread_start+0xe0
> C [libsystem_pthread.dylib+0x2443] thread_start+0xf

LGTM.

-------------

Marked as reviewed by lucy (Reviewer).

PR Review: https://git.openjdk.org/jdk/pull/18908#pullrequestreview-2019585061