SW4STM32 and SW4Linux fully supports the STM32MP1 asymmetric multicore Cortex/A7+M4 MPUs

   With System Workbench for Linux, Embedded Linux on the STM32MP1 family of MPUs from ST was never as simple to build and maintain, even for newcomers in the Linux world.
And, if you install System Workbench for Linux in System Workbench for STM32 you can seamlessly develop and debug asymmetric applications running partly on Linux, partly on the Cortex-M4.
You can get more information from the ac6-tools website and download two short videos (registration required) highlighting:

System Workbench for STM32

malloc heap issue with CubeMX Project

I recently encountered the same problem and fixed it with the modification on _sbrk in syscall.c shown above.
This topic is quite old. But CubeMX still generates this faulty syscall.c when RTOS is used.

By the way, this effect is also responsible for printf float creating a hard fault when using with -u _printf_float and RTOS.

Im am using CubeMX 5.4.0 on a STM32L4R7Z