On 4/18/19 7:47 PM, Laszlo Ersek wrote:
> RH covscan justifiedly reports that accessing
> "EFI_COMMON_SECTION_HEADER.Size", which is of type UINT8[3], through a
> (UINT32*), is undefined behavior:
>
>> Error: OVERRUN (CWE-119):
>> edk2-89910a39dcfd/OvmfPkg/Sec/SecMain.c:178: overrun-local: Overrunning
>> array of 3 bytes at byte offset 3 by dereferencing pointer
>> "(UINT32 *)((EFI_COMMON_SECTION_HEADER *)(UINTN)Section)->Size".
>> # 176| Section = (EFI_COMMON_SECTION_HEADER*)(UINTN) CurrentAddress;
>> # 177|
>> # 178|-> Size = SECTION_SIZE (Section);
>> # 179| if (Size < sizeof (*Section)) {
>> # 180| return EFI_VOLUME_CORRUPTED;
>
> Fix this by accessing the array elements individually.
>
> Cc: Liming Gao <liming....@intel.com>
> Cc: Michael D Kinney <michael.d.kin...@intel.com>
> Bugzilla: https://bugzilla.tianocore.org/show_bug.cgi?id=1710
> Issue: scan-1007.txt
> Signed-off-by: Laszlo Ersek <ler...@redhat.com>
> ---
>
> Notes:
> v2:
>
> - replace EFI_COMMON_SECTION_HEADER_UNION with individual array element
> access [Jordan, Phil, Mike]
>
> MdePkg/Include/Pi/PiFirmwareFile.h | 11 +++++++++--
> 1 file changed, 9 insertions(+), 2 deletions(-)
>
> diff --git a/MdePkg/Include/Pi/PiFirmwareFile.h
> b/MdePkg/Include/Pi/PiFirmwareFile.h
> index a9f3bcc4eb8e..05470538de42 100644
> --- a/MdePkg/Include/Pi/PiFirmwareFile.h
> +++ b/MdePkg/Include/Pi/PiFirmwareFile.h
> @@ -480,8 +480,15 @@ typedef struct {
> CHAR16 VersionString[1];
> } EFI_VERSION_SECTION2;
>
> -#define SECTION_SIZE(SectionHeaderPtr) \
> - ((UINT32) (*((UINT32 *) ((EFI_COMMON_SECTION_HEADER *) (UINTN)
> SectionHeaderPtr)->Size) & 0x00ffffff))
> +///
> +/// The argument passed as the SectionHeaderPtr parameter to the
> SECTION_SIZE()
> +/// and IS_SECTION2() function-like macros below must not have side effects:
> +/// SectionHeaderPtr is evaluated multiple times.
> +///
> +#define SECTION_SIZE(SectionHeaderPtr) ((UINT32) ( \
> + (((EFI_COMMON_SECTION_HEADER *) (UINTN) (SectionHeaderPtr))->Size[0]
> ) | \
> + (((EFI_COMMON_SECTION_HEADER *) (UINTN) (SectionHeaderPtr))->Size[1] <<
> 8) | \
> + (((EFI_COMMON_SECTION_HEADER *) (UINTN) (SectionHeaderPtr))->Size[2] <<
> 16)))
>
> #define IS_SECTION2(SectionHeaderPtr) \
> (SECTION_SIZE (SectionHeaderPtr) == 0x00ffffff)
>
Thanks!
Reviewed-by: Philippe Mathieu-Daude <phi...@redhat.com>
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