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nbd/server: Silence clang sanitizer warning

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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 <peter.maydell@linaro.org>
Fixes: 3b1f244c59 (nbd: Allow export of multiple bitmaps for one device)
Signed-off-by: Eric Blake <eblake@redhat.com>
Message-Id: <20211115223943.626416-1-eblake@redhat.com>
Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>
This commit is contained in:
Eric Blake 2021-11-15 16:39:43 -06:00
parent 9f0f846465
commit 76df2b8d69
1 changed files with 9 additions and 4 deletions
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13
nbd/server.c
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@ -1,5 +1,5 @@
/*
* Copyright (C) 2016-2020 Red Hat, Inc.
* Copyright (C) 2016-2021 Red Hat, Inc.
* Copyright (C) 2005 Anthony Liguori <anthony@codemonkey.ws>
*
* 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);