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SubjectRE: [PATCH V3 3/7] Drivers: hv: vmbus: add APIs to send/recv hvsock packet and get the r/w-ability
Date
> From: Dan Carpenter
> Sent: Thursday, July 23, 2015 18:25
> On Thu, Jul 23, 2015 at 01:10:57PM +0300, Dan Carpenter wrote:
> > In this specific case, writing it as "if (ret != 0)" caused the bug. If
> > we had written it as "if (ret) return ret;" then there are no zeroes so
> > wouldn't have been any temptation to return the zero instead of the ret.
>
> I did a search to see if returning the zero instead of the ret was a
> common mistake and it seems like it might be. I did:
>
> grep 'if (ret != 0)' drivers/ -r -A1 -n | grep "return 0;" | perl -ne 's/.c-(\d+)-/.c:$1/;
> print'
>
> drivers/gpu/drm/nouveau/nouveau_display.c:111 return 0;
> drivers/regulator/wm8400-regulator.c:47 return 0;
> drivers/platform/x86/dell-laptop.c:859 return 0;
> drivers/media/dvb-frontends/dibx000_common.c:213 return 0;
> drivers/media/dvb-frontends/dibx000_common.c:217 return 0;
> drivers/media/dvb-frontends/dibx000_common.c:235 return 0;
> drivers/media/dvb-frontends/dibx000_common.c:239 return 0;
> drivers/hv/channel.c:898 return 0;
> drivers/hv/channel.c:944 return 0;
>
> A bunch of those look suspicious but I don't know the subsystems well
> enough to be sure. Can you check the last two?
>
> dan carpenter

Thanks, Dan!

After I checked the code, I think there is no issue for the last two:
in the case of "if (ret != 0) return 0;", the output parameter buffer_actual_len is
zero and it is explicitly checked by the callers.
This may seem not natural and I think we can improve it in future.

BTW, at the end of vmbus_recvpacket(), the "return 0;" should be "return ret;", but
since the output parameter buffer_actual_len is checked by the callers, I think it's
OK for now.

Thanks,
-- Dexuan


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