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[PATCH 4/6] migration: Check xbzrle-cache-size more carefully


From: Markus Armbruster
Subject: [PATCH 4/6] migration: Check xbzrle-cache-size more carefully
Date: Fri, 13 Nov 2020 07:52:34 +0100

migrate-set-parameters passes the size to xbzrle_cache_resize().
xbzrle_cache_resize() checks it fits into size_t before it passes it
on to cache_init().  cache_init() checks it is a power of two no
smaller than @page_size.

cache_init() is also called from xbzrle_init(), bypassing
xbzrle_cache_resize()'s check.

Drop xbzrle_cache_resize()'s check, and check more carefully in
cache_init().

Signed-off-by: Markus Armbruster <armbru@redhat.com>
---
 migration/page_cache.c | 15 ++++-----------
 migration/ram.c        |  7 -------
 2 files changed, 4 insertions(+), 18 deletions(-)

diff --git a/migration/page_cache.c b/migration/page_cache.c
index b384f265fb..e07f4ad1dc 100644
--- a/migration/page_cache.c
+++ b/migration/page_cache.c
@@ -41,17 +41,10 @@ struct PageCache {
 PageCache *cache_init(uint64_t new_size, size_t page_size, Error **errp)
 {
     int64_t i;
-    size_t num_pages = new_size / page_size;
+    uint64_t num_pages = new_size / page_size;
     PageCache *cache;
 
-    if (new_size < page_size) {
-        error_setg(errp, QERR_INVALID_PARAMETER_VALUE, "cache size",
-                   "is smaller than one target page size");
-        return NULL;
-    }
-
-    /* round down to the nearest power of 2 */
-    if (!is_power_of_2(num_pages)) {
+    if (num_pages != (size_t)num_pages || !is_power_of_2(num_pages)) {
         error_setg(errp, QERR_INVALID_PARAMETER_VALUE, "cache size",
                    "is not a power of two number of pages");
         return NULL;
@@ -71,8 +64,8 @@ PageCache *cache_init(uint64_t new_size, size_t page_size, 
Error **errp)
     trace_migration_pagecache_init(cache->max_num_items);
 
     /* We prefer not to abort if there is no memory */
-    cache->page_cache = g_try_malloc((cache->max_num_items) *
-                                     sizeof(*cache->page_cache));
+    cache->page_cache = g_try_malloc_n(cache->max_num_items,
+                                       sizeof(*cache->page_cache));
     if (!cache->page_cache) {
         error_setg(errp, QERR_INVALID_PARAMETER_VALUE, "cache size",
                    "Failed to allocate page cache");
diff --git a/migration/ram.c b/migration/ram.c
index a84425d04f..d632ae694c 100644
--- a/migration/ram.c
+++ b/migration/ram.c
@@ -131,13 +131,6 @@ int xbzrle_cache_resize(uint64_t new_size, Error **errp)
     PageCache *new_cache;
     int64_t ret = 0;
 
-    /* Check for truncation */
-    if (new_size != (size_t)new_size) {
-        error_setg(errp, QERR_INVALID_PARAMETER_VALUE, "cache size",
-                   "exceeding address space");
-        return -1;
-    }
-
     if (new_size == migrate_xbzrle_cache_size()) {
         /* nothing to do */
         return 0;
-- 
2.26.2




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