Starting qemu with the following arguments causes qemu to segfault:
... -device lsi,id=lsi0 -drive file=iscsi:<...>,format=raw,if=none,node-name=
iscsi1 -device scsi-block,bus=lsi0.0,id=<...>,drive=iscsi1
This patch fixes blk_aio_ioctl() so it does not pass stack addresses to
blk_aio_ioctl_entry() which may be invoked after blk_aio_ioctl() returns. More
details about the bug follow.
blk_aio_ioctl() invokes blk_aio_prwv() with blk_aio_ioctl_entry as the
coroutine parameter. blk_aio_prwv() ultimately calls aio_co_enter().
When blk_aio_ioctl() is executed from within a coroutine context (e.g.
iscsi_bh_cb()), aio_co_enter() adds the coroutine (blk_aio_ioctl_entry) to
the current coroutine's wakeup queue. blk_aio_ioctl() then returns.
When blk_aio_ioctl_entry() executes later, it accesses an invalid pointer:
....
BlkRwCo *rwco = &acb->rwco;
rwco->ret = blk_co_ioctl(rwco->blk, rwco->offset,
rwco->qiov->iov[0].iov_base); <--- qiov is
invalid here
...
In the case when blk_aio_ioctl() is called from a non-coroutine context,
blk_aio_ioctl_entry() executes immediately. But if bdrv_co_ioctl() calls
qemu_coroutine_yield(), blk_aio_ioctl() will return. When the coroutine
execution is complete, control returns to blk_aio_ioctl_entry() after the call
to blk_co_ioctl(). There is no invalid reference after this point, but the
function is still holding on to invalid pointers.
The fix is to change blk_aio_prwv() to accept a void pointer for the IO buffer
rather than a QEMUIOVector. blk_aio_prwv() passes this through in BlkRwCo and
the
coroutine function casts it to QEMUIOVector or uses the void pointer directly.
Signed-off-by: Deepa Srinivasan <deepa.sriniva...@oracle.com>
Signed-off-by: Konrad Rzeszutek Wilk <konrad.w...@oracle.com>
Reviewed-by: Mark Kanda <mark.ka...@oracle.com>
---
block/block-backend.c | 51 +++++++++++++++++++++++++--------------------------
1 file changed, 25 insertions(+), 26 deletions(-)
diff --git a/block/block-backend.c b/block/block-backend.c
index baef8e7..2d0d9b6 100644
--- a/block/block-backend.c
+++ b/block/block-backend.c
@@ -1140,7 +1140,7 @@ int coroutine_fn blk_co_pwritev(BlockBackend *blk,
int64_t offset,
typedef struct BlkRwCo {
BlockBackend *blk;
int64_t offset;
- QEMUIOVector *qiov;
+ void *iobuf;
int ret;
BdrvRequestFlags flags;
} BlkRwCo;
@@ -1148,17 +1148,19 @@ typedef struct BlkRwCo {
static void blk_read_entry(void *opaque)
{
BlkRwCo *rwco = opaque;
+ QEMUIOVector *qiov = rwco->iobuf;
- rwco->ret = blk_co_preadv(rwco->blk, rwco->offset, rwco->qiov->size,
- rwco->qiov, rwco->flags);
+ rwco->ret = blk_co_preadv(rwco->blk, rwco->offset, qiov->size,
+ qiov, rwco->flags);
}
static void blk_write_entry(void *opaque)
{
BlkRwCo *rwco = opaque;
+ QEMUIOVector *qiov = rwco->iobuf;
- rwco->ret = blk_co_pwritev(rwco->blk, rwco->offset, rwco->qiov->size,
- rwco->qiov, rwco->flags);
+ rwco->ret = blk_co_pwritev(rwco->blk, rwco->offset, qiov->size,
+ qiov, rwco->flags);
}
static int blk_prw(BlockBackend *blk, int64_t offset, uint8_t *buf,
@@ -1178,7 +1180,7 @@ static int blk_prw(BlockBackend *blk, int64_t offset,
uint8_t *buf,
rwco = (BlkRwCo) {
.blk = blk,
.offset = offset,
- .qiov = &qiov,
+ .iobuf = &qiov,
.flags = flags,
.ret = NOT_DONE,
};
@@ -1275,7 +1277,7 @@ static void blk_aio_complete_bh(void *opaque)
}
static BlockAIOCB *blk_aio_prwv(BlockBackend *blk, int64_t offset, int bytes,
- QEMUIOVector *qiov, CoroutineEntry co_entry,
+ void *iobuf, CoroutineEntry co_entry,
BdrvRequestFlags flags,
BlockCompletionFunc *cb, void *opaque)
{
@@ -1287,7 +1289,7 @@ static BlockAIOCB *blk_aio_prwv(BlockBackend *blk,
int64_t offset, int bytes,
acb->rwco = (BlkRwCo) {
.blk = blk,
.offset = offset,
- .qiov = qiov,
+ .iobuf = iobuf,
.flags = flags,
.ret = NOT_DONE,
};
@@ -1310,10 +1312,11 @@ static void blk_aio_read_entry(void *opaque)
{
BlkAioEmAIOCB *acb = opaque;
BlkRwCo *rwco = &acb->rwco;
+ QEMUIOVector *qiov = rwco->iobuf;
- assert(rwco->qiov->size == acb->bytes);
+ assert(qiov->size == acb->bytes);
rwco->ret = blk_co_preadv(rwco->blk, rwco->offset, acb->bytes,
- rwco->qiov, rwco->flags);
+ qiov, rwco->flags);
blk_aio_complete(acb);
}
@@ -1321,10 +1324,11 @@ static void blk_aio_write_entry(void *opaque)
{
BlkAioEmAIOCB *acb = opaque;
BlkRwCo *rwco = &acb->rwco;
+ QEMUIOVector *qiov = rwco->iobuf;
- assert(!rwco->qiov || rwco->qiov->size == acb->bytes);
+ assert(!qiov || qiov->size == acb->bytes);
rwco->ret = blk_co_pwritev(rwco->blk, rwco->offset, acb->bytes,
- rwco->qiov, rwco->flags);
+ qiov, rwco->flags);
blk_aio_complete(acb);
}
@@ -1453,8 +1457,10 @@ int blk_co_ioctl(BlockBackend *blk, unsigned long int
req, void *buf)
static void blk_ioctl_entry(void *opaque)
{
BlkRwCo *rwco = opaque;
+ QEMUIOVector *qiov = rwco->iobuf;
+
rwco->ret = blk_co_ioctl(rwco->blk, rwco->offset,
- rwco->qiov->iov[0].iov_base);
+ qiov->iov[0].iov_base);
}
int blk_ioctl(BlockBackend *blk, unsigned long int req, void *buf)
@@ -1467,24 +1473,15 @@ static void blk_aio_ioctl_entry(void *opaque)
BlkAioEmAIOCB *acb = opaque;
BlkRwCo *rwco = &acb->rwco;
- rwco->ret = blk_co_ioctl(rwco->blk, rwco->offset,
- rwco->qiov->iov[0].iov_base);
+ rwco->ret = blk_co_ioctl(rwco->blk, rwco->offset, rwco->iobuf);
+
blk_aio_complete(acb);
}
BlockAIOCB *blk_aio_ioctl(BlockBackend *blk, unsigned long int req, void *buf,
BlockCompletionFunc *cb, void *opaque)
{
- QEMUIOVector qiov;
- struct iovec iov;
-
- iov = (struct iovec) {
- .iov_base = buf,
- .iov_len = 0,
- };
- qemu_iovec_init_external(&qiov, &iov, 1);
-
- return blk_aio_prwv(blk, req, 0, &qiov, blk_aio_ioctl_entry, 0, cb,
opaque);
+ return blk_aio_prwv(blk, req, 0, buf, blk_aio_ioctl_entry, 0, cb, opaque);
}
int blk_co_pdiscard(BlockBackend *blk, int64_t offset, int bytes)
@@ -1900,7 +1897,9 @@ int blk_truncate(BlockBackend *blk, int64_t offset,
PreallocMode prealloc,
static void blk_pdiscard_entry(void *opaque)
{
BlkRwCo *rwco = opaque;
- rwco->ret = blk_co_pdiscard(rwco->blk, rwco->offset, rwco->qiov->size);
+ QEMUIOVector *qiov = rwco->iobuf;
+
+ rwco->ret = blk_co_pdiscard(rwco->blk, rwco->offset, qiov->size);
}
int blk_pdiscard(BlockBackend *blk, int64_t offset, int bytes)
--
2.7.4
