[lld] r341670 - MachO: Fix out-of-bounds memory access in getString16

[Tom Stellard via llvm-commits]

On 09/07/2018 08:42 AM, Tom Stellard via llvm-commits wrote:
> Author: tstellar
> Date: Fri Sep  7 08:42:01 2018
> New Revision: 341670
> 
> URL: http://llvm.org/viewvc/llvm-project?rev=341670&view=rev
> Log:
> MachO: Fix out-of-bounds memory access in getString16
> 
> Summary:
> This fixes the following tests when gcc is compiled with gcc8:
> 
> lld :: mach-o/do-not-emit-unwind-fde-arm64.yaml
> lld :: mach-o/eh-frame-relocs-arm64.yaml
> 
> llvm.org/PR38096
> 

Hans,

This is a fix for the release blocker: llvm.org/PR38096.  Is ths
OK to merge to the release_70 branch?

-Tom

> Reviewers: lhames, kledzik, javed.absar
> 
> Subscribers: kristof.beyls, llvm-commits
> 
> Differential Revision: https://reviews.llvm.org/D51547
> 
> Modified:
>     lld/trunk/lib/ReaderWriter/MachO/MachONormalizedFileBinaryUtils.h
> 
> Modified: lld/trunk/lib/ReaderWriter/MachO/MachONormalizedFileBinaryUtils.h
> URL: http://llvm.org/viewvc/llvm-project/lld/trunk/lib/ReaderWriter/MachO/MachONormalizedFileBinaryUtils.h?rev=341670&r1=341669&r2=341670&view=diff
> ==============================================================================
> --- lld/trunk/lib/ReaderWriter/MachO/MachONormalizedFileBinaryUtils.h (original)
> +++ lld/trunk/lib/ReaderWriter/MachO/MachONormalizedFileBinaryUtils.h Fri Sep  7 08:42:01 2018
> @@ -185,12 +185,11 @@ packRelocation(const Relocation &r, bool
>    return result;
>  }
>  
> -inline StringRef getString16(const char s[16]) {
> -  StringRef x = s;
> -  if ( x.size() > 16 )
> -    return x.substr(0, 16);
> -  else
> -    return x;
> +static StringRef getString16(const char s[16]) {
> +  // The StringRef(const char *) constructor passes the const char * to
> +  // strlen(), so we can't use this constructor here, because if there is no
> +  // null terminator in s, then strlen() will read past the end of the array.
> +  return StringRef(s, strnlen(s, 16));
>  }
>  
>  inline void setString16(StringRef str, char s[16]) {
> 
> 
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