From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:43345) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1epK3P-0004dh-4R for qemu-devel@nongnu.org; Fri, 23 Feb 2018 15:34:54 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1epK3N-0000Df-MC for qemu-devel@nongnu.org; Fri, 23 Feb 2018 15:34:51 -0500 References: <1513385953-5466-1-git-send-email-deepa.srinivasan@oracle.com> <20180129155153.GM20446@stefanha-x1.localdomain> From: Deepa Srinivasan Message-ID: <2a617f25-33c1-d4b2-5150-357f1d6e5492@oracle.com> Date: Fri, 23 Feb 2018 12:34:36 -0800 MIME-Version: 1.0 In-Reply-To: <20180129155153.GM20446@stefanha-x1.localdomain> Content-Type: text/plain; charset=windows-1252; format=flowed Content-Transfer-Encoding: 7bit Content-Language: en-US Subject: Re: [Qemu-devel] [Qemu-block] [PATCH v2] block: Fix qemu crash when using scsi-block List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Stefan Hajnoczi , Kevin Wolf Cc: qemu-block@nongnu.org, Konrad Rzeszutek Wilk , qemu-devel@nongnu.org, mreitz@redhat.com, stefanha@redhat.com, pbonzini@redhat.com Stefan, Kevin - Ping, to take this patch. Thanks. On 01/29/2018 07:51 AM, Stefan Hajnoczi wrote: > On Fri, Dec 15, 2017 at 04:59:13PM -0800, Deepa Srinivasan wrote: >> 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 >> Signed-off-by: Konrad Rzeszutek Wilk >> Reviewed-by: Mark Kanda >> --- >> block/block-backend.c | 51 +++++++++++++++++++++++++-------------------------- > Kevin: Ping. Will you take this through your tree? > >> 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 >> >>