From: Jia-Ju Bai <baijiaju1...@gmail.com> Date: Fri, 26 Jan 2018 22:17:08 +0800
> > > On 2018/1/26 21:56, Jia-Ju Bai wrote: >> >> >> On 2018/1/26 20:05, Al Viro wrote: >>> On Fri, Jan 26, 2018 at 04:00:27PM +0800, Jia-Ju Bai wrote: >>>> After checking all possible call chains to fs_send() here, >>>> my tool finds that fs_send() is never called in atomic context. >>>> And this function is assigned to a function pointer "dev->ops->send", >>>> which is only called by vcc_sendmsg() (net/atm/common.c) >>>> through vcc->dev->ops->send(), and vcc_sendmsg() calls schedule(), >>>> it indicates that fs_send() can call functions which may sleep. >>>> 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. >>> The trouble is, places like >>> net/atm/raw.c:65: vcc->send = atm_send_aal0; >>> net/atm/raw.c:74: vcc->send = vcc->dev->ops->send; >>> net/atm/raw.c:83: vcc->send = vcc->dev->ops->send; >>> mean extra call chains. It's *not* just vcc_sendmsg(), and e.g. >>> ret = ATM_SKB(skb)->vcc->send(ATM_SKB(skb)->vcc, skb) >>> ? DROP_PACKET : 1; >>> bh_unlock_sock(sk_atm(vcc)); >>> in pppoatm_send() definitely is called under a spinlock. >>> >>> Looking through the driver (in advanced bitrot, as usual for >>> drivers/atm), >>> I'd say that submit_queue() is fucked in head in the "queue full" >>> case. >>> And judging by the history, had been thus since the original merge... >> >> Thanks for reply :) >> >> I am sorry for this false positive. >> I think other ATM related patches that I submitted are also false >> positives, sorry. >> My tool did not handle this situation of passing function pointer, and >> I will improve the tool... >> >> >> Thanks, >> Jia-Ju Bai > > I check the code again, and confirm only my patches about "send" are > false positives. > I think other my patches that are about "open" does not has this > problem: > https://marc.info/?l=linux-kernel&m=151693791432626&w=2 > https://marc.info/?l=linux-kernel&m=151695475503314&w=2 > https://marc.info/?l=linux-kernel&m=151693150131512&w=2 > > I hope you can have a check :) No, _you_ have a check. All of these patches will be dropped, sorry.
