Hide OpenSSL tricks from Valgrind far-reaching initialization errors.

This change has no effect unless ./configured --with-valgrind-debug.

OpenSSL, including its Assembly code, contains many optimizations and
timing defenses that Valgrind misinterprets as uninitialized value
usage. Most of those tricks can be disabled by #defining PURIFY when
building OpenSSL, but some are not protected with PURIFY and most
OpenSSL libraries are (and should be) built without that #define.

To make matters worse, once Valgrind misdetects uninitialized memory, it
will complain about every usage of that memory. Those complaints create
a lot of noise, complicate triage, and effectively mask true bugs.
AFAICT, they cannot be suppressed by listing the source of that memory.

For example, this OpenSSL Assembly trick:
    Uninitialised value was created by a stack allocation
       at 0x556C2F7: aesni_cbc_encrypt (aesni-x86_64.s:2081)

Triggers many false errors like this one:
    Conditional jump or move depends on uninitialised value(s)
       by 0x750838: Debug::Finish()
       by 0x942E68: Http::One::ResponseParser::parse(SBuf const&)
       ...

This change marks OpenSSL-returned decrypted bytes as initialized. This
might miss some true OpenSSL bugs, but we should focus on Squid bugs.

diff --git a/src/ssl/support.cc b/src/ssl/support.cc
index 075bfd7a30136f9733f58379d67b624224ab567f..26eeb17d21ce014f090c0dfda9ff1561f101ff51 100644 (file)
--- a/src/ssl/support.cc
+++ b/src/ssl/support.cc
@@ -707,6 +707,9 @@ ssl_read_method(int fd, char *buf, int len)
 #endif
 
     int i = SSL_read(ssl, buf, len);
+    if (i > 0) {
+        (void)VALGRIND_MAKE_MEM_DEFINED(buf, i);
+    }
 
     if (i > 0 && SSL_pending(ssl) > 0) {
         debugs(83, 2, "SSL FD " << fd << " is pending");