From b8d7519352ba8c6df83259295d4a3bad093cae90 Mon Sep 17 00:00:00 2001 From: Jakub Kicinski Date: Fri, 15 May 2026 15:13:25 -0700 Subject: net: shaper: rework the VALID marking (again) Recent commit changed the semantics from NOT_VALID to VALID. I didn't realize that the flags are not stored atomically with the entry in XArray. There's still a race of reader observing a VALID mark for a slot, getting interrupted, writer replacing the entry with a different one, reader continuing, fetching the entry which is now a different pointer than the pointer for which VALID was meant. The biggest consequence of this is that we may see a UAF since net_shaper_rollback() assumed that entries without VALID can be freed without observing RCU. Looks like the XArray marks are buying us nothing at this point. Let's convert the code to an explicit valid field. The smp_load_acquire() / smp_store_release() barriers are marginally cleaner. Reported-by: Sashiko Fixes: 93954b40f6a4 ("net-shapers: implement NL set and delete operations") Reviewed-by: Simon Horman Link: https://patch.msgid.link/20260515221325.1685455-3-kuba@kernel.org Signed-off-by: Jakub Kicinski --- include/net/net_shaper.h | 1 + 1 file changed, 1 insertion(+) (limited to 'include') diff --git a/include/net/net_shaper.h b/include/net/net_shaper.h index 5c3f49b52fe9..3939b816b001 100644 --- a/include/net/net_shaper.h +++ b/include/net/net_shaper.h @@ -53,6 +53,7 @@ struct net_shaper { /* private: */ u32 leaves; /* accounted only for NODE scope */ + bool valid; struct rcu_head rcu; }; -- cgit v1.2.3