+-- On Fri, 4 Sep 2020, P J P wrote --+ | 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;
Ping...! (needs review) -- Prasad J Pandit / Red Hat Product Security Team 8685 545E B54C 486B C6EB 271E E285 8B5A F050 DE8D