CVE-2024-42109

In the Linux kernel, the following vulnerability has been resolved:<br /> <br /> netfilter: nf_tables: unconditionally flush pending work before notifier<br /> <br /> syzbot reports:<br /> <br /> KASAN: slab-uaf in nft_ctx_update include/net/netfilter/nf_tables.h:1831<br /> KASAN: slab-uaf in nft_commit_release net/netfilter/nf_tables_api.c:9530<br /> KASAN: slab-uaf int nf_tables_trans_destroy_work+0x152b/0x1750 net/netfilter/nf_tables_api.c:9597<br /> Read of size 2 at addr ffff88802b0051c4 by task kworker/1:1/45<br /> [..]<br /> Workqueue: events nf_tables_trans_destroy_work<br /> Call Trace:<br /> nft_ctx_update include/net/netfilter/nf_tables.h:1831 [inline]<br /> nft_commit_release net/netfilter/nf_tables_api.c:9530 [inline]<br /> nf_tables_trans_destroy_work+0x152b/0x1750 net/netfilter/nf_tables_api.c:9597<br /> <br /> Problem is that the notifier does a conditional flush, but its possible<br /> that the table-to-be-removed is still referenced by transactions being<br /> processed by the worker, so we need to flush unconditionally.<br /> <br /> We could make the flush_work depend on whether we found a table to delete<br /> in nf-next to avoid the flush for most cases.<br /> <br /> AFAICS this problem is only exposed in nf-next, with<br /> commit e169285f8c56 ("netfilter: nf_tables: do not store nft_ctx in transaction objects"),<br /> with this commit applied there is an unconditional fetch of<br /> table-&gt;family which is whats triggering the above splat.