RFR: 8275640 (win) java.net.NetworkInterface issues with IPv6-only environments [v3]

[Mark Sheppard]

On Sat, 8 Jan 2022 09:11:05 GMT, Daniel Jelinski <duke at openjdk.java.net> wrote:

>> Clean up of various issues related to error handling and memory management
>
> Daniel Jelinski has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Address problems reported by clang-tidy

src/java.base/windows/native/libnet/NetworkInterface_winXP.c line 271:

> 269:     curr = *netifPP;
> 270:     ret = lookupIPAddrTable(env, &tableP);
> 271:     if (ret == -1) {

on the face of it, this change looks reasonable as one might think "let the processing continue for IPv6", however it introduces some problems in subsequent processing. Most notably, it assigns a NULL value to tableP , which is then fed to the function enumAddresses_win_ipaddrtable and this performs a sanity check for tableP == NULL and returns 0. Also enumAddresses_win_ipaddrtable takes the inout parameter netaddr *netaddrP; which is a local variable (stack variable) which hasn't been properly initialized and only has a valid value assigned for a successful return from enumAddresses_win_ipaddrtable. Thus, this inout varaiable has indeterminates values (i.e. what ever is on the stack) which are then assigned in the else block (for the return 0 case)
 else{
            curr->addrs = netaddrP;
            curr->naddrs += ret;
            curr = curr->next;
        }
and so subsequent indeterminate processing and potental crash is significant as the netif data structures spurious pointer assignments

I think the current coded return policy is good, but should probably include *netifPP = NULL as nothing is being returned.

The function getAllInterfacesAndAddresses also inconsistently handles the out value of *netifPP as it is not always assigned a value in enumAddresses_win_ipaddrtable. As such the addition of call to free_netif  on this pointer may lead to indeterminate behavious -- Thus the assignment and update of netifPP needs to be addressed

src/java.base/windows/native/libnet/NetworkInterface_winXP.c line 285:

> 283:         ret = enumAddresses_win_ipaddrtable(env, curr, &netaddrP, tableP);
> 284:         if (ret < 0) {
> 285:             free_netif(*netifPP);

seems like the right thing to do, but *netifPP may not be properly assigned a valid pointer

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PR: https://git.openjdk.java.net/jdk/pull/6090