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block: Fix qemu crash when using scsi-block

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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.srinivasan@oracle.com>
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Reviewed-by: Mark Kanda <mark.kanda@oracle.com>
Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
This commit is contained in:
Deepa Srinivasan 2017-12-15 16:59:13 -08:00 committed by Stefan Hajnoczi
parent 0ab4537f08
commit c060332c76
1 changed files with 25 additions and 26 deletions
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51
block/block-backend.c
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@ -1150,7 +1150,7 @@ 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;
@ -1158,17 +1158,19 @@ 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,
@ -1188,7 +1190,7 @@ 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,
};
@ -1296,7 +1298,7 @@ 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)
{
@ -1308,7 +1310,7 @@ 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,
};
@ -1331,10 +1333,11 @@ 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);
}
@ -1342,10 +1345,11 @@ 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);
}
@ -1474,8 +1478,10 @@ 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)
@ -1488,24 +1494,15 @@ 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)
@ -1949,7 +1946,9 @@ 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)