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block/iscsi: fix ioctl cancel use-after-free

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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 <felipe@nutanix.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Message-Id: <20180203061621.7033-4-stefanha@redhat.com>
Reviewed-by: Felipe Franciosi <felipe@nutanix.com>
Tested-by: Sreejith Mohanan <sreejit.mohanan@nutanix.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Stefan Hajnoczi 2018-02-03 07:16:21 +01:00 committed by Paolo Bonzini
parent 83d11973fa
commit c100448790
1 changed files with 19 additions and 4 deletions
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23
block/iscsi.c
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@ -124,6 +124,7 @@ 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 */
@ -287,6 +288,7 @@ 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)
@ -295,6 +297,7 @@ 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
@ -303,14 +306,25 @@ 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;
}
/* 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);
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 */
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 = {
@ -1008,6 +1022,7 @@ 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);