From ef0d243bfeaf1da8854c26f89536dc1b69c56602 Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?Marek=20Marczykowski-G=C3=B3recki?= Date: Wed, 16 Dec 2015 05:51:10 +0100 Subject: [PATCH 12/13] xen-blkfront: make local copy of response before using it MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Organization: Invisible Things Lab Cc: Marek Marczykowski-Górecki Data on the shared page can be changed at any time by the backend. Make a local copy, which is no longer controlled by the backend. And only then access it. This is part of XSA155. CC: stable@vger.kernel.org Signed-off-by: Marek Marczykowski-Górecki --- drivers/block/xen-blkfront.c | 34 +++++++++++++++++----------------- 1 file changed, 17 insertions(+), 17 deletions(-) diff --git a/drivers/block/xen-blkfront.c b/drivers/block/xen-blkfront.c index 2fee2ee..5d7eb04 100644 --- a/drivers/block/xen-blkfront.c +++ b/drivers/block/xen-blkfront.c @@ -1296,7 +1296,7 @@ static void blkif_completion(struct blk_shadow *s, struct blkfront_info *info, static irqreturn_t blkif_interrupt(int irq, void *dev_id) { struct request *req; - struct blkif_response *bret; + struct blkif_response bret; RING_IDX i, rp; unsigned long flags; struct blkfront_ring_info *rinfo = (struct blkfront_ring_info *)dev_id; @@ -1316,8 +1316,8 @@ static irqreturn_t blkif_interrupt(int irq, void *dev_id) for (i = rinfo->ring.rsp_cons; i != rp; i++) { unsigned long id; - bret = RING_GET_RESPONSE(&rinfo->ring, i); - id = bret->id; + RING_COPY_RESPONSE(&rinfo->ring, i, &bret); + id = bret.id; /* * The backend has messed up and given us an id that we would * never have given to it (we stamp it up to BLK_RING_SIZE - @@ -1325,35 +1325,35 @@ static irqreturn_t blkif_interrupt(int irq, void *dev_id) */ if (id >= BLK_RING_SIZE(info)) { WARN(1, "%s: response to %s has incorrect id (%ld)\n", - info->gd->disk_name, op_name(bret->operation), id); + info->gd->disk_name, op_name(bret.operation), id); /* We can't safely get the 'struct request' as * the id is busted. */ continue; } req = rinfo->shadow[id].request; - if (bret->operation != BLKIF_OP_DISCARD) { + if (bret.operation != BLKIF_OP_DISCARD) { /* * We may need to wait for an extra response if the * I/O request is split in 2 */ - if (!blkif_completion(&id, rinfo, bret)) + if (!blkif_completion(&id, rinfo, &bret)) continue; } if (add_id_to_freelist(rinfo, id)) { WARN(1, "%s: response to %s (id %ld) couldn't be recycled!\n", - info->gd->disk_name, op_name(bret->operation), id); + info->gd->disk_name, op_name(bret.operation), id); continue; } - error = (bret->status == BLKIF_RSP_OKAY) ? 0 : -EIO; - switch (bret->operation) { + error = (bret.status == BLKIF_RSP_OKAY) ? 0 : -EIO; + switch (bret.operation) { case BLKIF_OP_DISCARD: - if (unlikely(bret->status == BLKIF_RSP_EOPNOTSUPP)) { + if (unlikely(bret.status == BLKIF_RSP_EOPNOTSUPP)) { struct request_queue *rq = info->rq; printk(KERN_WARNING "blkfront: %s: %s op failed\n", - info->gd->disk_name, op_name(bret->operation)); + info->gd->disk_name, op_name(bret.operation)); error = -EOPNOTSUPP; info->feature_discard = 0; info->feature_secdiscard = 0; @@ -1358,15 +1358,15 @@ static irqreturn_t blkif_interrupt(int irq, void *dev_id) break; case BLKIF_OP_FLUSH_DISKCACHE: case BLKIF_OP_WRITE_BARRIER: - if (unlikely(bret->status == BLKIF_RSP_EOPNOTSUPP)) { + if (unlikely(bret.status == BLKIF_RSP_EOPNOTSUPP)) { printk(KERN_WARNING "blkfront: %s: %s op failed\n", - info->gd->disk_name, op_name(bret->operation)); + info->gd->disk_name, op_name(bret.operation)); error = -EOPNOTSUPP; } - if (unlikely(bret->status == BLKIF_RSP_ERROR && + if (unlikely(bret.status == BLKIF_RSP_ERROR && rinfo->shadow[id].req.u.rw.nr_segments == 0)) { printk(KERN_WARNING "blkfront: %s: empty %s op failed\n", - info->gd->disk_name, op_name(bret->operation)); + info->gd->disk_name, op_name(bret.operation)); error = -EOPNOTSUPP; } if (unlikely(error)) { @@ -1378,9 +1378,9 @@ static irqreturn_t blkif_interrupt(int irq, void *dev_id) /* fall through */ case BLKIF_OP_READ: case BLKIF_OP_WRITE: - if (unlikely(bret->status != BLKIF_RSP_OKAY)) + if (unlikely(bret.status != BLKIF_RSP_OKAY)) dev_dbg(&info->xbdev->dev, "Bad return from blkdev data " - "request: %x\n", bret->status); + "request: %x\n", bret.status); blk_mq_complete_request(req, error); break; -- 2.1.0