On Mon, 2018-01-22 at 22:53 -0800, Yonghong Song wrote:
> In commit b471f2f1de8b ("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: b471f2f1de8b ("bpf: implement MAP_GET_NEXT_KEY command for LPM_TRIE
> map")
> Signed-off-by: Yonghong Song <y...@fb.com>
Reported-by: syzbot <syzkal...@googlegroups.com>
Reviewed-by: Eric Dumazet <eduma...@google.com>
Thanks.
> ---
> kernel/bpf/lpm_trie.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/kernel/bpf/lpm_trie.c b/kernel/bpf/lpm_trie.c
> index d7ea962..8f083ea 100644
> --- a/kernel/bpf/lpm_trie.c
> +++ b/kernel/bpf/lpm_trie.c
> @@ -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;
>
