From 76df2b8d695b07d85cce7db753a51cdbfe42b445 Mon Sep 17 00:00:00 2001 From: Eric Blake Date: Mon, 15 Nov 2021 16:39:43 -0600 Subject: nbd/server: Silence clang sanitizer warning MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit clang's sanitizer is picky: memset(NULL, x, 0) is technically undefined behavior, even though no sane implementation of memset() deferences the NULL. Caught by the nbd-qemu-allocation iotest. The alternative to checking before each memset is to instead force an allocation of 1 element instead of g_new0(type, 0)'s behavior of returning NULL for a 0-length array. Reported-by: Peter Maydell Fixes: 3b1f244c59 (nbd: Allow export of multiple bitmaps for one device) Signed-off-by: Eric Blake Message-Id: <20211115223943.626416-1-eblake@redhat.com> Reviewed-by: Philippe Mathieu-Daudé --- nbd/server.c | 13 +++++++++---- 1 file changed, 9 insertions(+), 4 deletions(-) (limited to 'nbd') diff --git a/nbd/server.c b/nbd/server.c index 6d03e8a..d9164ee 100644 --- a/nbd/server.c +++ b/nbd/server.c @@ -1,5 +1,5 @@ /* - * Copyright (C) 2016-2020 Red Hat, Inc. + * Copyright (C) 2016-2021 Red Hat, Inc. * Copyright (C) 2005 Anthony Liguori * * Network Block Device Server Side @@ -879,7 +879,9 @@ static bool nbd_meta_qemu_query(NBDClient *client, NBDExportMetaContexts *meta, if (!*query) { if (client->opt == NBD_OPT_LIST_META_CONTEXT) { meta->allocation_depth = meta->exp->allocation_depth; - memset(meta->bitmaps, 1, meta->exp->nr_export_bitmaps); + if (meta->exp->nr_export_bitmaps) { + memset(meta->bitmaps, 1, meta->exp->nr_export_bitmaps); + } } trace_nbd_negotiate_meta_query_parse("empty"); return true; @@ -894,7 +896,8 @@ static bool nbd_meta_qemu_query(NBDClient *client, NBDExportMetaContexts *meta, if (nbd_strshift(&query, "dirty-bitmap:")) { trace_nbd_negotiate_meta_query_parse("dirty-bitmap:"); if (!*query) { - if (client->opt == NBD_OPT_LIST_META_CONTEXT) { + if (client->opt == NBD_OPT_LIST_META_CONTEXT && + meta->exp->nr_export_bitmaps) { memset(meta->bitmaps, 1, meta->exp->nr_export_bitmaps); } trace_nbd_negotiate_meta_query_parse("empty"); @@ -1024,7 +1027,9 @@ static int nbd_negotiate_meta_queries(NBDClient *client, /* enable all known contexts */ meta->base_allocation = true; meta->allocation_depth = meta->exp->allocation_depth; - memset(meta->bitmaps, 1, meta->exp->nr_export_bitmaps); + if (meta->exp->nr_export_bitmaps) { + memset(meta->bitmaps, 1, meta->exp->nr_export_bitmaps); + } } else { for (i = 0; i < nb_queries; ++i) { ret = nbd_negotiate_meta_query(client, meta, errp); -- cgit v1.1