Re: [edk2-devel] [PATCH v2 1/1] MdePkg : UefiFileHandleLib: fix buffer overrun in FileHandleReadLine()

["Zhiguang Liu" <zhiguang.liu@intel.com>]

Reviewed-by: Zhiguang Liu <zhiguang.liu@intel.com>

> -----Original Message-----
> From: devel@edk2.groups.io <devel@edk2.groups.io> On Behalf Of Vladimir
> Olovyannikov via groups.io
> Sent: Thursday, July 2, 2020 10:31 AM
> To: devel@edk2.groups.io
> Cc: Vladimir Olovyannikov <vladimir.olovyannikov@broadcom.com>; Kinney,
> Michael D <michael.d.kinney@intel.com>; Gao, Liming
> <liming.gao@intel.com>; Liu, Zhiguang <zhiguang.liu@intel.com>
> Subject: [edk2-devel] [PATCH v2 1/1] MdePkg : UefiFileHandleLib: fix buffer
> overrun in FileHandleReadLine()
> 
> If the size of the supplied buffer in FileHandleReadLine(), module
> UefiFileHandleLib.c, was not 0, but was not enough to fit in
> the line, the size is increased, and then the Buffer of the new
> size is zeroed. This size is always larger than the supplied buffer size,
> causing supplied buffer overrun. Fix the issue by using the
> supplied buffer size in ZeroMem().
> 
> Signed-off-by: Vladimir Olovyannikov
> <vladimir.olovyannikov@broadcom.com>
> Cc: Michael D Kinney <michael.d.kinney@intel.com>
> Cc: Liming Gao <liming.gao@intel.com>
> Cc: Zhiguang Liu <zhiguang.liu@intel.com>
> ---
>  MdePkg/Library/UefiFileHandleLib/UefiFileHandleLib.c | 6 ++++--
>  1 file changed, 4 insertions(+), 2 deletions(-)
> 
> diff --git a/MdePkg/Library/UefiFileHandleLib/UefiFileHandleLib.c
> b/MdePkg/Library/UefiFileHandleLib/UefiFileHandleLib.c
> index 28e28e5f67d5..ab34e6ccd5f4 100644
> --- a/MdePkg/Library/UefiFileHandleLib/UefiFileHandleLib.c
> +++ b/MdePkg/Library/UefiFileHandleLib/UefiFileHandleLib.c
> @@ -969,6 +969,7 @@ FileHandleReadLine(
>    UINTN       CharSize;
> 
>    UINTN       CountSoFar;
> 
>    UINTN       CrCount;
> 
> +  UINTN       OldSize;
> 
>    UINT64      OriginalFilePosition;
> 
> 
> 
>    if (Handle == NULL
> 
> @@ -1039,10 +1040,11 @@ FileHandleReadLine(
>    // if we ran out of space tell when...
> 
>    //
> 
>    if ((CountSoFar+1-CrCount)*sizeof(CHAR16) > *Size){
> 
> +    OldSize = *Size;
> 
>      *Size = (CountSoFar+1-CrCount)*sizeof(CHAR16);
> 
>      if (!Truncate) {
> 
> -      if (Buffer != NULL && *Size != 0) {
> 
> -        ZeroMem(Buffer, *Size);
> 
> +      if (Buffer != NULL && OldSize != 0) {
> 
> +        ZeroMem(Buffer, OldSize);
> 
>        }
> 
>        FileHandleSetPosition(Handle, OriginalFilePosition);
> 
>        return (EFI_BUFFER_TOO_SMALL);
> 
> --
> 2.26.2.266.ge870325ee8
> 
> 
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