net: caif: Fix a sleep-in-atomic bug in cfpkt_create_pfx

The kernel may sleep under a rcu read lock in cfpkt_create_pfx, and the
function call path is:
cfcnfg_linkup_rsp (acquire the lock by rcu_read_lock)
  cfctrl_linkdown_req
    cfpkt_create
      cfpkt_create_pfx
        alloc_skb(GFP_KERNEL) --> may sleep
cfserl_receive (acquire the lock by rcu_read_lock)
  cfpkt_split
    cfpkt_create_pfx
      alloc_skb(GFP_KERNEL) --> may sleep

There is "in_interrupt" in cfpkt_create_pfx to decide use "GFP_KERNEL" or
"GFP_ATOMIC". In this situation, "GFP_KERNEL" is used because the function
is called under a rcu read lock, instead in interrupt.

To fix it, only "GFP_ATOMIC" is used in cfpkt_create_pfx.

Signed-off-by: Jia-Ju Bai <baijiaju1990@163.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/net/caif/cfpkt_skbuff.c b/net/caif/cfpkt_skbuff.c
index 59ce1fcc220ce0a71fb57733be7cc91e6b8ac7fc..71b6ab240dea26b228be35ba24ec3f43772f19f7 100644 (file)
--- a/net/caif/cfpkt_skbuff.c
+++ b/net/caif/cfpkt_skbuff.c
@@ -81,11 +81,7 @@ static struct cfpkt *cfpkt_create_pfx(u16 len, u16 pfx)
 {
        struct sk_buff *skb;
 
-       if (likely(in_interrupt()))
-               skb = alloc_skb(len + pfx, GFP_ATOMIC);
-       else
-               skb = alloc_skb(len + pfx, GFP_KERNEL);
-
+       skb = alloc_skb(len + pfx, GFP_ATOMIC);
        if (unlikely(skb == NULL))
                return NULL;