Messages in this thread | | | Subject | Re: [PATCH] block: aoenet: Replace GFP_ATOMIC with GFP_KERNEL in aoenet_rcv | From | Ed Cashin <> | Date | Sun, 28 Jan 2018 10:40:36 -0500 |
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Good luck in your efforts, and thanks for your work on static analysis.
> On Jan 27, 2018, at 9:12 PM, Jia-Ju Bai <baijiaju1990@gmail.com> wrote: > > > >> On 2018/1/28 1:48, Ed Cashin wrote: >> If the tool cannot tell whether the protected state is manipulated by *another* piece of code called in atomic context, then it's insufficient. >> >>> On Jan 26, 2018, at 4:37 AM, Jia-Ju Bai <baijiaju1990@gmail.com> wrote: >>> >>> After checking all possible call chains to aoenet_rcv(), >>> my tool finds that aoenet_rcv() is never called in atomic context, >>> namely never in an interrupt handler or holding a spinlock. >>> Thus GFP_ATOMIC is not necessary, and it can be replaced with GFP_KERNEL. >>> >>> This is found by a static analysis tool named DCNS written by myself. >>> >>> Signed-off-by: Jia-Ju Bai <baijiaju1990@gmail.com> >>> --- >>> drivers/block/aoe/aoenet.c | 2 +- >>> 1 file changed, 1 insertion(+), 1 deletion(-) >>> >>> diff --git a/drivers/block/aoe/aoenet.c b/drivers/block/aoe/aoenet.c >>> index 63773a9..d5fff7a 100644 >>> --- a/drivers/block/aoe/aoenet.c >>> +++ b/drivers/block/aoe/aoenet.c >>> @@ -138,7 +138,7 @@ static int __init aoe_iflist_setup(char *str) >>> if (dev_net(ifp) != &init_net) >>> goto exit; >>> >>> - skb = skb_share_check(skb, GFP_ATOMIC); >>> + skb = skb_share_check(skb, GFP_KERNEL); >>> if (skb == NULL) >>> return 0; >>> if (!is_aoe_netif(ifp)) >>> -- >>> 1.7.9.5 >>> >>> > > Sorry, I find my report is false positive after I manually check the code. > aoenet_rcv() is used as function pointer via "->func", and it is called in dev_queue_xmit_nit() in net/core/dev.c. > dev_queue_xmit_nit() calls a rcu_read_lock() before it calls pt_prev->func(). > Thus it is right to use GFP_ATOMIC in aoenet_rcv(). > Sorry again for my incorrect report... > > Thanks, > Jia-Ju Bai
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