From 654580eee13bc7a0d4ed4cad2b2fead1ec88107a Mon Sep 17 00:00:00 2001 From: AKASHI Takahiro Date: Wed, 15 Nov 2023 10:53:45 +0900 Subject: [PATCH] xen: pvblock: fix the maximum io size in one operation The current implementation may cause BUG_ON() in blkfront_aio() BUG_ON(n > BLKIF_MAX_SEGMENTS_PER_REQUEST); In pvblock_iop(), a read/write operation will be split into smaller chunks of data so that the size in one access (aio_nbytes) is limited to, at the maximum, BLKIF_MAX_SEGMENTS_PER_REQUEST * PAGE_SIZE But this works only if when the *buffer* passed in to pvblock_io() is page-aligned. If not, the given data region may stand across (BLKIF_MAX_SEGMENTS_PER_REQUEST + 1) pages. See the logic in blkfront_aio(): start = (uintptr_t)aiocbp->aio_buf & PAGE_MASK; end = ((uintptr_t)aiocbp->aio_buf + aiocbp->aio_nbytes + PAGE_SIZE - 1) & PAGE_MASK; Then this will lead to BUG_ON() above. This can be fixed by decreasing the maximum size of aio_nbytes. Signed-off-by: AKASHI Takahiro Fixes: commit 3a739cc6c948 ("xen: pvblock: Implement front-back protocol and do IO") --- drivers/xen/pvblock.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/drivers/xen/pvblock.c b/drivers/xen/pvblock.c index 4ad548d599..1df04e239a 100644 --- a/drivers/xen/pvblock.c +++ b/drivers/xen/pvblock.c @@ -632,7 +632,8 @@ static ulong pvblock_iop(struct udevice *udev, lbaint_t blknr, memcpy(blk_dev->bounce_buffer, buffer, desc->blksz); aiocb.aio_nbytes = unaligned ? desc->blksz : - min((size_t)(BLKIF_MAX_SEGMENTS_PER_REQUEST * PAGE_SIZE), + min((size_t)((BLKIF_MAX_SEGMENTS_PER_REQUEST - 1) + * PAGE_SIZE), (size_t)(blocks_todo * desc->blksz)); blkfront_io(&aiocb, write); -- 2.39.5