From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001 From: Stefan Reiter Date: Tue, 2 Mar 2021 16:11:54 +0100 Subject: [PATCH] block/io: accept NULL qiov in bdrv_pad_request Some operations, e.g. block-stream, perform reads while discarding the results (only copy-on-read matters). In this case they will pass NULL as the target QEMUIOVector, which will however trip bdrv_pad_request, since it wants to extend its passed vector. If there is no qiov, no operation can be done with it, but the bytes and offset still need to be updated, so the subsequent aligned read will actually be aligned and not run into an assertion failure. Signed-off-by: Thomas Lamprecht [FE: do update bytes and offset in any case] Signed-off-by: Fiona Ebner --- block/io.c | 29 ++++++++++++++++------------- 1 file changed, 16 insertions(+), 13 deletions(-) diff --git a/block/io.c b/block/io.c index 83d1b1dfdc..e927881e40 100644 --- a/block/io.c +++ b/block/io.c @@ -1723,22 +1723,25 @@ static int bdrv_pad_request(BlockDriverState *bs, return 0; } - sliced_iov = qemu_iovec_slice(*qiov, *qiov_offset, *bytes, - &sliced_head, &sliced_tail, - &sliced_niov); - - /* Guaranteed by bdrv_check_request32() */ - assert(*bytes <= SIZE_MAX); - ret = bdrv_create_padded_qiov(bs, pad, sliced_iov, sliced_niov, - sliced_head, *bytes); - if (ret < 0) { - bdrv_padding_finalize(pad); - return ret; + if (qiov && *qiov) { + sliced_iov = qemu_iovec_slice(*qiov, *qiov_offset, *bytes, + &sliced_head, &sliced_tail, + &sliced_niov); + + /* Guaranteed by bdrv_check_request32() */ + assert(*bytes <= SIZE_MAX); + ret = bdrv_create_padded_qiov(bs, pad, sliced_iov, sliced_niov, + sliced_head, *bytes); + if (ret < 0) { + bdrv_padding_finalize(pad); + return ret; + } + *qiov = &pad->local_qiov; + *qiov_offset = 0; } + *bytes += pad->head + pad->tail; *offset -= pad->head; - *qiov = &pad->local_qiov; - *qiov_offset = 0; if (padded) { *padded = true; }