Re: [PATCH v1 1/3] MdeModulePkg/Dhcp4Dxe: Remove unnecessary NULL pointer check.

["Wu, Jiaxin" <jiaxin.wu@intel.com>]

Thanks Siyuan, I will double check that.



> -----Original Message-----
> From: Fu, Siyuan
> Sent: Friday, January 18, 2019 10:00 AM
> To: Wu, Jiaxin <jiaxin.wu@intel.com>; edk2-devel@lists.01.org
> Cc: Ye, Ting <ting.ye@intel.com>; Wu, Hao A <hao.a.wu@intel.com>; Gao,
> Liming <liming.gao@intel.com>
> Subject: RE: [PATCH v1 1/3] MdeModulePkg/Dhcp4Dxe: Remove
> unnecessary NULL pointer check.
> 
> Hi, Jiaxin
> 
> > -----Original Message-----
> > From: Wu, Jiaxin
> > Sent: Thursday, January 17, 2019 9:01 AM
> > To: edk2-devel@lists.01.org
> > Cc: Ye, Ting <ting.ye@intel.com>; Fu, Siyuan <siyuan.fu@intel.com>; Wu,
> Hao A
> > <hao.a.wu@intel.com>; Gao, Liming <liming.gao@intel.com>; Wu, Jiaxin
> > <jiaxin.wu@intel.com>
> > Subject: [PATCH v1 1/3] MdeModulePkg/Dhcp4Dxe: Remove unnecessary
> NULL pointer
> > check.
> >
> > REF: https://bugzilla.tianocore.org/show_bug.cgi?id=1469
> >
> > Since the value of Instance is retrieved from the list Entry,
> > it can't be the NULL pointer, so just remove the unnecessary
> > check.
> >
> > Cc: Ye Ting <ting.ye@intel.com>
> > Cc: Fu Siyuan <siyuan.fu@intel.com>
> > Cc: Wu Hao A <hao.a.wu@intel.com>
> > Cc: Gao Liming <liming.gao@intel.com>
> > Contributed-under: TianoCore Contribution Agreement 1.1
> > Signed-off-by: Wu Jiaxin <jiaxin.wu@intel.com>
> > ---
> >  MdeModulePkg/Universal/Network/Dhcp4Dxe/Dhcp4Io.c | 15 ++++++----
> -----
> >  1 file changed, 6 insertions(+), 9 deletions(-)
> >
> > diff --git a/MdeModulePkg/Universal/Network/Dhcp4Dxe/Dhcp4Io.c
> > b/MdeModulePkg/Universal/Network/Dhcp4Dxe/Dhcp4Io.c
> > index 98a22a77b4..04d47e0759 100644
> > --- a/MdeModulePkg/Universal/Network/Dhcp4Dxe/Dhcp4Io.c
> > +++ b/MdeModulePkg/Universal/Network/Dhcp4Dxe/Dhcp4Io.c
> > @@ -1,9 +1,9 @@
> >  /** @file
> >    EFI DHCP protocol implementation.
> >
> > -Copyright (c) 2006 - 2018, Intel Corporation. All rights reserved.<BR>
> > +Copyright (c) 2006 - 2019, Intel Corporation. All rights reserved.<BR>
> >  This program and the accompanying materials
> >  are licensed and made available under the terms and conditions of the BSD
> > License
> >  which accompanies this distribution.  The full text of the license may be
> > found at
> >  http://opensource.org/licenses/bsd-license.php
> >
> > @@ -1493,15 +1493,15 @@ DhcpOnTimerTick (
> >    IN EFI_EVENT              Event,
> >    IN VOID                   *Context
> >    )
> >  {
> >    LIST_ENTRY                *Entry;
> > -  LIST_ENTRY                *Next;
> >    DHCP_SERVICE              *DhcpSb;
> >    DHCP_PROTOCOL             *Instance;
> >    EFI_STATUS                Status;
> >
> > +  Entry    = NULL;
> >    DhcpSb   = (DHCP_SERVICE *) Context;
> >    Instance = DhcpSb->ActiveChild;
> >
> >    //
> >    // 0xffff is the maximum supported value for elapsed time according to
> RFC.
> > @@ -1644,18 +1644,15 @@ DhcpOnTimerTick (
> >
> >  ON_EXIT:
> >    //
> >    // Iterate through all the DhcpSb Children.
> >    //
> > -  NET_LIST_FOR_EACH_SAFE (Entry, Next, &DhcpSb->Children) {
> > +  NET_LIST_FOR_EACH (Entry, &DhcpSb->Children) {
> 
> The DHCP Instance might be destroyed in PxeDhcpDone (it singals upper
> layer that the DHCP is completed), and the NET_LIST_FOR_EACH is not
> delete-safe, you should not replace it with NET_LIST_FOR_EACH.
> 
> >      Instance = NET_LIST_USER_STRUCT (Entry, DHCP_PROTOCOL, Link);
> > -
> > -    if ((Instance != NULL) && (Instance->Token != NULL)) {
> > -      Instance->Timeout--;
> > -      if (Instance->Timeout == 0) {
> > -        PxeDhcpDone (Instance);
> > -      }
> > +    Instance->Timeout--;
> > +    if (Instance->Timeout == 0) {
> > +      PxeDhcpDone (Instance);
> >      }
> >    }
> >
> >    return ;
> >
> > --
> > 2.17.1.windows.2