[PATCH 4.9 009/172] net: caif: Fix a sleep-in-atomic bug in cfpkt_create_pfx

From: Greg Kroah-Hartman
Date: Mon Jul 03 2017 - 10:35:55 EST

4.9-stable review patch. If anyone has any objections, please let me know.


From: Jia-Ju Bai <baijiaju1990@xxxxxxx>

[ Upstream commit f146e872eb12ebbe92d8e583b2637e0741440db3 ]

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)
alloc_skb(GFP_KERNEL) --> may sleep
cfserl_receive (acquire the lock by rcu_read_lock)
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@xxxxxxx>
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
net/caif/cfpkt_skbuff.c | 6 +-----
1 file changed, 1 insertion(+), 5 deletions(-)

--- a/net/caif/cfpkt_skbuff.c
+++ b/net/caif/cfpkt_skbuff.c
@@ -81,11 +81,7 @@ static struct cfpkt *cfpkt_create_pfx(u1
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;