hw/ide/pci.c in QEMU before 5.1.1 can trigger a NULL pointer dereference because it lacks a pointer check before an ide_cancel_dma_sync call.
https://ruhr-uni-bochum.sciebo.de/s/NNWP2GfwzYKeKwE?path=%2Fide_nullptr1b
https://lists.nongnu.org/archive/html/qemu-devel/2020-09/msg05967.html