In the Linux kernel, the following vulnerability has been resolved:

lockd: fix swapped arguments in nlmsvc match ip()

When releasing locks by server IP address via /proc/fs/nfsd/unlock ip, nlmsvc unlock all by ip() calls nlm traverse files() with the server sockaddr as the opaque @data argument:

nlm traverse files(server addr, nlmsvc match ip, NULL);

The match callback is later invoked from nlm traverse locks() as:

match(lockhost, host);

where the first argument is the nlm host that owns the lock, and the second argument is the @data that was originally passed down (here the server sockaddr). This is the convention every other match callback relies on (nlmsvc mark host(), nlmsvc same host(), nlmsvc is client()): arg1 is the real nlm host, arg2 is the caller-supplied reference value.

nlmsvc match ip() has had these two arguments reversed ever since the unlock-by-IP feature was introduced in commit 4373ea84c84d ("lockd: unlock lockd locks associated with a given server ip"):

return rpc cmp addr(nlm srcaddr(host), datap);

Here @host is actually the server sockaddr, so nlm srcaddr(host) dereferences a struct sockaddr as a struct nlm host and reads garbage at the offset of h srcaddr; meanwhile @datap is actually the lock owner's nlm host but is compared as a sockaddr. As a result the comparison practically never matches and locks are not released for the requested IP.

Swap the arguments so the lock owner's source address is compared against the requested server address:

return rpc cmp addr(nlm srcaddr(datap), (struct sockaddr *)host);

[ cel: fix the misleading typedef parameter names too ]