In function GetMediaInfo(), the following expression:
ScsiDiskDevice->BlkIo.Media->LastBlock = (Capacity10->LastLba3 << 24) |
(Capacity10->LastLba2 << 16) |
(Capacity10->LastLba1 << 8) |
Capacity10->LastLba0;
will involve undefined behavior in signed left shift operations.
Since Capacity10->LastLbaX is of type UINT8, and
ScsiDiskDevice->BlkIo.Media->LastBlock is of type UINT64. Therefore,
Capacity10->LastLbaX will be promoted to int (32 bits, signed) first,
and then perform the left shift operation.
According to the C11 spec, Section 6.5.7:
4 The result of E1 << E2 is E1 left-shifted E2 bit positions; vacated
bits are filled with zeros. If E1 has an unsigned type, the value
of the result is E1 * 2^E2 , reduced modulo one more than the
maximum value representable in the result type. If E1 has a signed
type and nonnegative value, and E1 * 2^E2 is representable in the
result type, then that is the resulting value; otherwise, the
behavior is undefined.
So if bit 7 of Capacity10->LastLba3 is 1, (Capacity10->LastLba3 << 24)
will be out of the range within int type. The undefined behavior of the
signed left shift will lead to a potential of setting the high 32 bits
of ScsiDiskDevice->BlkIo.Media->LastBlock to 1 during the cast from type
int to type UINT64.
This commit will add an explicit UINT32 type cast for
Capacity10->LastLba3 to resolve this issue.
Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Hao Wu <hao.a.wu@intel.com>
Reviewed-by: Feng Tian <feng.tian@intel.com>
Reviewed-by: Laszlo Ersek <lersek@redhat.com>
7c115e775b