netfilter: nft_compat: use refcnt_t type for nft_xt reference count
Using standard integer type was fine while all operations on it were
guarded by the nftnl subsys mutex.
This isn't true anymore:
1. transactions are guarded only by a pernet mutex, so concurrent
rule manipulation in different netns is racy
2. the ->destroy hook runs from a work queue after the transaction
mutex has been released already.
cpu0 cpu1 (net 1) cpu2 (net 2)
nft_compat->destroy nft_compat->init nft_compat->init
if (--nft_xt->ref == 0) nft_xt->ref++ nft_xt->ref++
Switch to refcount_t. Doing this however only fixes a minor aspect,
nft_compat also performs linked-list operations in an unsafe way.
This is addressed in the next two patches.
Fixes: f102d66b335a ("netfilter: nf_tables: use dedicated mutex to guard transactions")
Fixes: 0935d5588400 ("netfilter: nf_tables: asynchronous release")
Reported-by: Taehee Yoo <firstname.lastname@example.org>
Signed-off-by: Florian Westphal <email@example.com>
Signed-off-by: Pablo Neira Ayuso <firstname.lastname@example.org>
1 file changed