scsi: mpi3mr: Fix issues in mpi3mr_get_all_tgt_info()

In the Linux kernel, the following vulnerability has been resolved:

scsi: mpi3mr: Fix issues in mpi3mr_get_all_tgt_info()

The function mpi3mr_get_all_tgt_info() has four issues:

1) It calculates valid entry length in alltgt_info assuming the header part
of the struct mpi3mr_device_map_info would equal to sizeof(u32). The
correct size is sizeof(u64).

2) When it calculates the valid entry length kern_entrylen, it excludes one
entry by subtracting 1 from num_devices.

3) It copies num_device by calling memcpy(). Substitution is enough.

4) It does not specify the calculated length to sg_copy_from_buffer().
Instead, it specifies the payload length which is larger than the
alltgt_info size. It causes "BUG: KASAN: slab-out-of-bounds".

Fix the issues by using the correct header size, removing the subtraction
from num_devices, replacing the memcpy() with substitution and specifying
the correct length to sg_copy_from_buffer().