481939 - _PR_ImplicitInitialization sends uninitialized bytes to getsockopt

Status: RESOLVED INVALID

(NSPR :: NSPR, defect)

Description

[Jesse Ruderman]

Mozilla/5.0 (Macintosh; U; Intel Mac OS X 10.5; en-US; rv:1.9.2a1pre) Gecko/20090304 Minefield/3.2a1pre

Starting Firefox (Mac, mozilla-central, opt) under Valgrind gives me:

==4831== Syscall param socketcall.getsockopt(optlen) points to uninitialised byte(s)
==4831==    at 0x7C7302: getsockopt (in /usr/lib/libSystem.B.dylib)
==4831==    by 0x57BFD: _PR_ImplicitInitialization (in /Users/jruderman/central/opt-obj/nsprpub/pr/src/libnspr4.dylib)
==4831==    by 0x4D721: PR_NewLogModule (in /Users/jruderman/central/opt-obj/nsprpub/pr/src/libnspr4.dylib)
==4831==    by 0x20080CB: __static_initialization_and_destruction_0(int, int) (in /Users/jruderman/central/opt-obj/toolkit/library/XUL)
==4831==    by 0x8FE12F35: ImageLoaderMachO::doModInitFunctions(ImageLoader::LinkContext const&) (in /usr/lib/dyld)
==4831==    by 0x8FE0E7E2: ImageLoader::recursiveInitialization(ImageLoader::LinkContext const&, unsigned int) (in /usr/lib/dyld)
==4831==    by 0x8FE0E774: ImageLoader::recursiveInitialization(ImageLoader::LinkContext const&, unsigned int) (in /usr/lib/dyld)
==4831==    by 0x8FE0E8C8: ImageLoader::runInitializers(ImageLoader::LinkContext const&) (in /usr/lib/dyld)
==4831==    by 0x8FE04101: dyld::initializeMainExecutable() (in /usr/lib/dyld)
==4831==    by 0x8FE07BCE: dyld::_main(mach_header const*, unsigned long, int, char const**, char const**, char const**) (in /usr/lib/dyld)
==4831==    by 0x8FE01871: dyldbootstrap::start(mach_header const*, int, char const**, long) (in /usr/lib/dyld)
==4831==    by 0x8FE01036: _dyld_start (in /usr/lib/dyld)
==4831==  Address 0xbfffe25c is on thread 1's stack
==4831==  Uninitialised value was created by a stack allocation
==4831==    at 0x62A00: _PR_InitIO (in /Users/jruderman/central/opt-obj/nsprpub/pr/src/libnspr4.dylib)

Comment 1

[Wan-Teh Chang]

Here is the code in question:

1161 #ifdef _PR_IPV6_V6ONLY_PROBE
1162     /* In Mac OS X v10.3 Panther Beta the IPV6_V6ONLY socket option
1163      * is turned on by default, contrary to what RFC 3493, Section
1164      * 5.3 says.  So we have to turn it off.  Find out whether we
1165      * are running on such a system.
1166      */
1167     {
1168         int osfd;
1169         osfd = socket(AF_INET6, SOCK_STREAM, 0);
1170         if (osfd != -1) {
1171             int on;  <=== UNINITIALIZED
1172             int optlen = sizeof(on);
1173             if (getsockopt(osfd, IPPROTO_IPV6, IPV6_V6ONLY,
1174                     &on, &optlen) == 0) {
1175                 _pr_ipv6_v6only_on_by_default = on;
1176             }
1177             close(osfd);
1178         }
1179     }
1180 #endif

The variable 'on' is uninitialized because it will receive
output from getsockopt.

Does Valgrind blindly require all output arguments to be
initialized?

Comment 2

[Wan-Teh Chang]

Sorry, I didn't read the Valgrind message carefully.

Valgrind says:
Syscall param socketcall.getsockopt(optlen) points to uninitialised
byte(s)

But optlen is initialized!

Comment 3

[Jesse Ruderman]

Nicholas, can you help wtc figure this out?

Comment 4

[Nicholas Nethercote [inactive]]

It might be a bug in Valgrind.  I'll take a closer look on Tuesday (Monday's a public holiday in Australia...)

Comment 5

[Nicholas Nethercote [inactive]]

Sorry for the delay.  It was a bug in Valgrind's getsockopt() wrapper for Darwin.
If you update your version of Valgrind from the DARWIN branch it should be fixed.