On 2020/9/1 17:12, Laszlo Ersek wrote:
> Currently the (SecDataDirLeft <= sizeof (WIN_CERTIFICATE)) check only
> guards the de-referencing of the "WinCertificate" pointer. It does not
> guard the calculation of the pointer itself:
>
> WinCertificate = (WIN_CERTIFICATE *) (mImageBase + OffSet);
>
> This is wrong; if we don't know for sure that we have enough room for a
> WIN_CERTIFICATE, then even creating such a pointer, not just
> de-referencing it, may invoke undefined behavior.
>
> Move the pointer calculation after the size check.
>
> Cc: Jian J Wang <jian.j.w...@intel.com>
> Cc: Jiewen Yao <jiewen....@intel.com>
> Cc: Min Xu <min.m...@intel.com>
> Cc: Wenyi Xie <xiewen...@huawei.com>
> Ref: https://bugzilla.tianocore.org/show_bug.cgi?id=2215
> Signed-off-by: Laszlo Ersek <ler...@redhat.com>
Tested-by: Wenyi Xie <xiewen...@huawei.com>
> ---
> SecurityPkg/Library/DxeImageVerificationLib/DxeImageVerificationLib.c | 8
> +++++---
> 1 file changed, 5 insertions(+), 3 deletions(-)
>
> diff --git
> a/SecurityPkg/Library/DxeImageVerificationLib/DxeImageVerificationLib.c
> b/SecurityPkg/Library/DxeImageVerificationLib/DxeImageVerificationLib.c
> index 377feebb205a..100739eb3eb6 100644
> --- a/SecurityPkg/Library/DxeImageVerificationLib/DxeImageVerificationLib.c
> +++ b/SecurityPkg/Library/DxeImageVerificationLib/DxeImageVerificationLib.c
> @@ -1855,10 +1855,12 @@ DxeImageVerificationHandler (
> for (OffSet = SecDataDir->VirtualAddress;
> OffSet < SecDataDirEnd;
> OffSet += (WinCertificate->dwLength + ALIGN_SIZE
> (WinCertificate->dwLength))) {
> - WinCertificate = (WIN_CERTIFICATE *) (mImageBase + OffSet);
> SecDataDirLeft = SecDataDirEnd - OffSet;
> - if (SecDataDirLeft <= sizeof (WIN_CERTIFICATE) ||
> - SecDataDirLeft < WinCertificate->dwLength) {
> + if (SecDataDirLeft <= sizeof (WIN_CERTIFICATE)) {
> + break;
> + }
> + WinCertificate = (WIN_CERTIFICATE *) (mImageBase + OffSet);
> + if (SecDataDirLeft < WinCertificate->dwLength) {
> break;
> }
>
>
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