iscsi_aio_cancel() does not increment the request's reference count, causing a use-after-free when ABORT TASK finishes after the request has already completed.
There are some additional issues with iscsi_aio_cancel(): 1. Several ABORT TASKs may be sent for the same task if iscsi_aio_cancel() is invoked multiple times. It's better to avoid this just in case the command identifier is reused. 2. The iscsilun->mutex protection is missing in iscsi_aio_cancel(). Reported-by: Felipe Franciosi <fel...@nutanix.com> Signed-off-by: Stefan Hajnoczi <stefa...@redhat.com> --- block/iscsi.c | 21 ++++++++++++++++++--- 1 file changed, 18 insertions(+), 3 deletions(-) diff --git a/block/iscsi.c b/block/iscsi.c index 1cfe1c647c..8140baac15 100644 --- a/block/iscsi.c +++ b/block/iscsi.c @@ -119,6 +119,7 @@ typedef struct IscsiAIOCB { #ifdef __linux__ sg_io_hdr_t *ioh; #endif + bool cancelled; } IscsiAIOCB; /* libiscsi uses time_t so its enough to process events every second */ @@ -282,6 +283,7 @@ static void iscsi_co_init_iscsitask(IscsiLun *iscsilun, struct IscsiTask *iTask) }; } +/* Called (via iscsi_service) with QemuMutex held. */ static void iscsi_abort_task_cb(struct iscsi_context *iscsi, int status, void *command_data, void *private_data) @@ -290,6 +292,7 @@ iscsi_abort_task_cb(struct iscsi_context *iscsi, int status, void *command_data, acb->status = -ECANCELED; iscsi_schedule_bh(acb); + qemu_aio_unref(acb); /* acquired in iscsi_aio_cancel() */ } static void @@ -298,14 +301,25 @@ iscsi_aio_cancel(BlockAIOCB *blockacb) IscsiAIOCB *acb = (IscsiAIOCB *)blockacb; IscsiLun *iscsilun = acb->iscsilun; - if (acb->status != -EINPROGRESS) { + qemu_mutex_lock(&iscsilun->mutex); + + /* If it was cancelled or completed already, our work is done here */ + if (acb->cancelled || acb->status != -EINPROGRESS) { + qemu_mutex_unlock(&iscsilun->mutex); return; } + acb->cancelled = true; + + qemu_aio_ref(acb); /* released in iscsi_abort_task_cb() */ + /* send a task mgmt call to the target to cancel the task on the target */ - iscsi_task_mgmt_abort_task_async(iscsilun->iscsi, acb->task, - iscsi_abort_task_cb, acb); + if (iscsi_task_mgmt_abort_task_async(iscsilun->iscsi, acb->task, + iscsi_abort_task_cb, acb) < 0) { + qemu_aio_unref(acb); /* since iscsi_abort_task_cb() won't be called */ + } + qemu_mutex_unlock(&iscsilun->mutex); } static const AIOCBInfo iscsi_aiocb_info = { @@ -1000,6 +1014,7 @@ static BlockAIOCB *iscsi_aio_ioctl(BlockDriverState *bs, acb->bh = NULL; acb->status = -EINPROGRESS; acb->ioh = buf; + acb->cancelled = false; if (req != SG_IO) { iscsi_ioctl_handle_emulated(acb, req, buf); -- 2.14.3