From: Prasad J Pandit <p...@fedoraproject.org> When cancelling an i/o operation via ide_cancel_dma_sync(), a block pointer may be null. Add check to avoid null pointer dereference.
-> https://ruhr-uni-bochum.sciebo.de/s/NNWP2GfwzYKeKwE?path=%2Fide_nullptr1 ==1803100==Hint: address points to the zero page. #0 blk_bs ../block/block-backend.c:714 #1 blk_drain ../block/block-backend.c:1715 #2 ide_cancel_dma_sync ../hw/ide/core.c:723 #3 bmdma_cmd_writeb ../hw/ide/pci.c:298 #4 bmdma_write ../hw/ide/piix.c:75 #5 memory_region_write_accessor ../softmmu/memory.c:483 #6 access_with_adjusted_size ../softmmu/memory.c:544 #7 memory_region_dispatch_write ../softmmu/memory.c:1465 #8 flatview_write_continue ../exec.c:3176 ... Reported-by: Ruhr-University <bugs-sys...@rub.de> Signed-off-by: Prasad J Pandit <p...@fedoraproject.org> --- hw/ide/core.c | 1 + hw/ide/pci.c | 5 ++++- 2 files changed, 5 insertions(+), 1 deletion(-) Update v2: use an assert() call -> https://lists.nongnu.org/archive/html/qemu-devel/2020-08/msg08336.html diff --git a/hw/ide/core.c b/hw/ide/core.c index f76f7e5234..8105187f49 100644 --- a/hw/ide/core.c +++ b/hw/ide/core.c @@ -718,6 +718,7 @@ void ide_cancel_dma_sync(IDEState *s) * whole DMA operation will be submitted to disk with a single * aio operation with preadv/pwritev. */ + assert(s->blk); if (s->bus->dma->aiocb) { trace_ide_cancel_dma_sync_remaining(); blk_drain(s->blk); diff --git a/hw/ide/pci.c b/hw/ide/pci.c index b50091b615..b47e675456 100644 --- a/hw/ide/pci.c +++ b/hw/ide/pci.c @@ -295,7 +295,10 @@ void bmdma_cmd_writeb(BMDMAState *bm, uint32_t val) /* Ignore writes to SSBM if it keeps the old value */ if ((val & BM_CMD_START) != (bm->cmd & BM_CMD_START)) { if (!(val & BM_CMD_START)) { - ide_cancel_dma_sync(idebus_active_if(bm->bus)); + IDEState *s = idebus_active_if(bm->bus); + if (s->blk) { + ide_cancel_dma_sync(s); + } bm->status &= ~BM_STATUS_DMAING; } else { bm->cur_addr = bm->addr; -- 2.26.2
