INVSTATE hard fault with SPI interrupt handler. STM32F405

[AWats.4]

I'm attempting to have my program run some code when a SPI transfer is complete using the RXNE flag. Setting the RXNEIE bit invokes SPI2_IRQHandler() as expected but it always results in a hard fault (CFSR register = 0x20000), without any additions to SPI2_IRQHandler().

I don't have much experience in debugging of this kind so any help/tips would be appreciated.

[Tesla DeLorean]

Perhaps break-point the code an step it?

Make sure all the call-back addresses in the structure are properly populated

[AWats.4]

Reading the spi data register and clearing the RXNE flag in the first line of the interrupt handler seems to have fixed it.