Commit 2310035f authored Jan 22, 2018 by Yonghong Song Committed by Daniel Borkmann Jan 23, 2018

bpf: fix incorrect kmalloc usage in lpm_trie MAP_GET_NEXT_KEY rcu region

In commit b471f2f1 ("bpf: implement MAP_GET_NEXT_KEY command for LPM_TRIE map"),
the implemented MAP_GET_NEXT_KEY callback function is guarded with rcu read lock.
In the function body, "kmalloc(size, GFP_USER | __GFP_NOWARN)" is used which may
sleep and violate rcu read lock region requirements. This patch fixed the issue
by using GFP_ATOMIC instead to avoid blocking kmalloc. Tested with
CONFIG_DEBUG_ATOMIC_SLEEP=y as suggested by Eric Dumazet.

Fixes: b471f2f1 ("bpf: implement MAP_GET_NEXT_KEY command for LPM_TRIE map")
Signed-off-by: Yonghong Song <yhs@fb.com>
Reported-by: syzbot <syzkaller@googlegroups.com>
Reviewed-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>

parent e8a22b5f

kernel/bpf/lpm_trie.c

+1 −1

Original line number	Diff line number	Diff line
		@@ -624,7 +624,7 @@ static int trie_get_next_key(struct bpf_map map, void _key, void *_next_key)
		}

		node_stack = kmalloc(trie->max_prefixlen * sizeof(struct lpm_trie_node *),
		GFP_USER \| __GFP_NOWARN);
		GFP_ATOMIC \| __GFP_NOWARN);
		if (!node_stack)
		return -ENOMEM;