Re: [PATCH] MdePkg/BasePrintLib: Fix incorrect Precision position calculation

["Wang, Jian J" <jian.j.wang@intel.com>]

I revisit the code again. You're right that the commit log is not correct.
The '\0' would be read and even the one pass it.

Regards,
Jian


> -----Original Message-----
> From: Kinney, Michael D
> Sent: Thursday, December 28, 2017 12:38 AM
> To: Wang, Jian J <jian.j.wang@intel.com>; edk2-devel@lists.01.org; Kinney,
> Michael D <michael.d.kinney@intel.com>
> Cc: Yao, Jiewen <jiewen.yao@intel.com>; Zeng, Star <star.zeng@intel.com>;
> Gao, Liming <liming.gao@intel.com>
> Subject: RE: [edk2] [PATCH] MdePkg/BasePrintLib: Fix incorrect Precision
> position calculation
> 
> Is the commit log correct?
> 
> Is the issue that the character past the '\0' could be read?
> 
> Mike
> 
> > -----Original Message-----
> > From: Wang, Jian J
> > Sent: Tuesday, December 26, 2017 6:14 PM
> > To: Wang, Jian J <jian.j.wang@intel.com>; edk2-
> > devel@lists.01.org
> > Cc: Kinney, Michael D <michael.d.kinney@intel.com>; Yao,
> > Jiewen <jiewen.yao@intel.com>; Zeng, Star
> > <star.zeng@intel.com>; Gao, Liming <liming.gao@intel.com>
> > Subject: RE: [edk2] [PATCH] MdePkg/BasePrintLib: Fix
> > incorrect Precision position calculation
> >
> > Mike and Liming,
> >
> > Could you take a look at this patch?
> >
> > Regards,
> > Jian
> >
> >
> > > -----Original Message-----
> > > From: edk2-devel [mailto:edk2-devel-
> > bounces@lists.01.org] On Behalf Of Jian J
> > > Wang
> > > Sent: Monday, December 25, 2017 10:09 AM
> > > To: edk2-devel@lists.01.org
> > > Cc: Kinney, Michael D <michael.d.kinney@intel.com>;
> > Yao, Jiewen
> > > <jiewen.yao@intel.com>; Zeng, Star
> > <star.zeng@intel.com>; Gao, Liming
> > > <liming.gao@intel.com>
> > > Subject: [edk2] [PATCH] MdePkg/BasePrintLib: Fix
> > incorrect Precision position
> > > calculation
> > >
> > > Due to the a potential hole in the stop condition of
> > for-loop, the two
> > > continuous access to ArgumentString (index, index+1)
> > inside the loop
> > > might cause the string ending character ('\0') to be
> > read.
> > >
> > > Cc: Michael D Kinney <michael.d.kinney@intel.com>
> > > Cc: Liming Gao <liming.gao@intel.com>
> > > Cc: Jiewen Yao <jiewen.yao@intel.com>
> > > Cc: Star Zeng <star.zeng@intel.com>
> > > Contributed-under: TianoCore Contribution Agreement 1.1
> > > Signed-off-by: Jian J Wang <jian.j.wang@intel.com>
> > > ---
> > >  MdePkg/Library/BasePrintLib/PrintLibInternal.c | 5
> > ++++-
> > >  1 file changed, 4 insertions(+), 1 deletion(-)
> > >
> > > diff --git
> > a/MdePkg/Library/BasePrintLib/PrintLibInternal.c
> > > b/MdePkg/Library/BasePrintLib/PrintLibInternal.c
> > > index 28d946472f..297d5a05b5 100644
> > > --- a/MdePkg/Library/BasePrintLib/PrintLibInternal.c
> > > +++ b/MdePkg/Library/BasePrintLib/PrintLibInternal.c
> > > @@ -1107,7 +1107,10 @@ BasePrintLibSPrintMarker (
> > >        // Compute the number of characters in
> > ArgumentString and store it in
> > > Count
> > >        // ArgumentString is either null-terminated, or
> > it contains Precision
> > > characters
> > >        //
> > > -      for (Count = 0; Count < Precision || ((Flags &
> > PRECISION) == 0); Count++) {
> > > +      for (Count = 0;
> > > +            ArgumentString[Count *
> > BytesPerArgumentCharacter] != '\0' &&
> > > +            (Count < Precision || ((Flags & PRECISION)
> > == 0));
> > > +              Count++) {
> > >          ArgumentCharacter = ((ArgumentString[Count *
> > > BytesPerArgumentCharacter] & 0xff) |
> > ((ArgumentString[Count *
> > > BytesPerArgumentCharacter + 1]) << 8)) & ArgumentMask;
> > >          if (ArgumentCharacter == 0) {
> > >            break;
> > > --
> > > 2.15.1.windows.2
> > >
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