From: Daniël Trujillo fib_table_lookup() checks the child index against the bounds before passing it to get_child_rcu(). The index is derived from the lookup key, which in turn is derived from flp->daddr. A userspace process can therefore influence the index by triggering lookups for chosen destination IPv4 addresses. If this bounds check is mispredicted as in-bounds, an out-of-bounds index can be transiently passed to get_child_rcu(). The value loaded beyond the child array is then treated as a node pointer. The next loop iteration dereferences that transient pointer through get_cindex(), causing a page-table walk whose cache footprint can leak (parts of) the pointer. Sanitize the index with array_index_nospec() before accessing the child array. Fixes: 9f9e636d4f89 ("fib_trie: Optimize fib_table_lookup to avoid wasting time on loops/variables") Cc: stable@vger.kernel.org Signed-off-by: Daniël Trujillo --- net/ipv4/fib_trie.c | 2 ++ 1 file changed, 2 insertions(+) diff --git a/net/ipv4/fib_trie.c b/net/ipv4/fib_trie.c index 248514dce0cd..bd8a368c5502 100644 --- a/net/ipv4/fib_trie.c +++ b/net/ipv4/fib_trie.c @@ -61,6 +61,7 @@ #include #include #include +#include #include #include #include @@ -1474,6 +1475,7 @@ int fib_table_lookup(struct fib_table *tb, const struct flowi4 *flp, cindex = index; } + index = array_index_nospec(index, 1ul << n->bits); n = get_child_rcu(n, index); if (unlikely(!n)) goto backtrace; --- base-commit: 37f12441f557468a56c1e27790413aa78c82afa2 change-id: 20261008-fib-trie-nospec-5c76028c8e7c Best regards, -- Daniël Trujillo