linux-kernel - [PATCH net] bpf: cpumap: use GFP_KERNEL instead of GFP_ATOMIC in __cpu_map_entry

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Date:   Wed, 14 Feb 2018 22:17:34 +0800
From:   Jason Wang <jasowang@...hat.com>
To:     ast@...nel.org, daniel@...earbox.net, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org
Cc:     mst@...hat.com, Jason Wang <jasowang@...hat.com>,
        Michal Hocko <mhocko@...nel.org>,
        Matthew Wilcox <willy@...radead.org>,
        Jesper Dangaard Brouer <brouer@...hat.com>,
        akpm@...ux-foundation.org, dhowells@...hat.com, hannes@...xchg.org
Subject: [PATCH net] bpf: cpumap: use GFP_KERNEL instead of GFP_ATOMIC in __cpu_map_entry_alloc()

There're several implications after commit 0bf7800f1799 ("ptr_ring:
try vmalloc() when kmalloc() fails") with the using of vmalloc() since
can't allow GFP_ATOMIC but mandate GFP_KERNEL. This will lead a WARN
since cpumap try to call with GFP_ATOMIC. Fortunately, entry
allocation of cpumap can only be done through syscall path which means
GFP_ATOMIC is not necessary, so fixing this by replacing GFP_ATOMIC
with GFP_KERNEL.

Reported-by: syzbot+1a240cdb1f4cc88819df@...kaller.appspotmail.com
Fixes: 0bf7800f1799 ("ptr_ring: try vmalloc() when kmalloc() fails")
Cc: Michal Hocko <mhocko@...nel.org>
Cc: Daniel Borkmann <daniel@...earbox.net>
Cc: Matthew Wilcox <willy@...radead.org>
Cc: Jesper Dangaard Brouer <brouer@...hat.com>
Cc: akpm@...ux-foundation.org
Cc: dhowells@...hat.com
Cc: hannes@...xchg.org
Signed-off-by: Jason Wang <jasowang@...hat.com>
---
 kernel/bpf/cpumap.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/bpf/cpumap.c b/kernel/bpf/cpumap.c
index fbfdada6..a4bb0b3 100644
--- a/kernel/bpf/cpumap.c
+++ b/kernel/bpf/cpumap.c
@@ -334,7 +334,7 @@ static int cpu_map_kthread_run(void *data)
 static struct bpf_cpu_map_entry *__cpu_map_entry_alloc(u32 qsize, u32 cpu,
 						       int map_id)
 {
-	gfp_t gfp = GFP_ATOMIC|__GFP_NOWARN;
+	gfp_t gfp = GFP_KERNEL | __GFP_NOWARN;
 	struct bpf_cpu_map_entry *rcpu;
 	int numa, err;
 
-- 
2.7.4