From c0d6740c1219f23f0b9a996f02c1ae9cf824b0b3 Mon Sep 17 00:00:00 2001

From: Kevin Wolf <kwolf@redhat.com>

Date: Thu, 6 Dec 2018 17:12:28 +0000

Subject: [PATCH 03/15] qcow2: Fix Coverity warning when calculating the

 refcount cache size

RH-Author: Kevin Wolf <kwolf@redhat.com>

Message-id: <20181206171240.5674-4-kwolf@redhat.com>

Patchwork-id: 83295

O-Subject: [RHEL-8.0 qemu-kvm PATCH 03/15] qcow2: Fix Coverity warning when calculating the refcount cache size

Bugzilla: 1656507

RH-Acked-by: Max Reitz <mreitz@redhat.com>

RH-Acked-by: John Snow <jsnow@redhat.com>

RH-Acked-by: Stefan Hajnoczi <stefanha@redhat.com>

From: Alberto Garcia <berto@igalia.com>

MIN_REFCOUNT_CACHE_SIZE is 4 and the cluster size is guaranteed to be

at most 2MB, so the minimum refcount cache size (in bytes) is always

going to fit in a 32-bit integer.

Coverity doesn't know that, and since we're storing the result in a

uint64_t (*refcount_cache_size) it thinks that we need the 64 bits and

that we probably want to do a 64-bit multiplication to prevent the

result from being truncated.

This is a false positive in this case, but it's a fair warning.

We could do a 64-bit multiplication to get rid of it, but since we

know that a 32-bit variable is enough to store this value let's simply

reuse min_refcount_cache, make it a normal int and stop doing casts.

Reported-by: Peter Maydell <peter.maydell@linaro.org>

Signed-off-by: Alberto Garcia <berto@igalia.com>

Reviewed-by: Eric Blake <eblake@redhat.com>

Signed-off-by: Kevin Wolf <kwolf@redhat.com>

(cherry picked from commit 7af5eea9b34ffb7a9a9fc25ba71998a02b76e159)

Signed-off-by: Kevin Wolf <kwolf@redhat.com>

Signed-off-by: Danilo C. L. de Paula <ddepaula@redhat.com>

---

 block/qcow2.c | 5 ++---

 1 file changed, 2 insertions(+), 3 deletions(-)

diff --git a/block/qcow2.c b/block/qcow2.c

index 4b65e4c..a0f7234 100644

--- a/block/qcow2.c

+++ b/block/qcow2.c

@@ -775,6 +775,7 @@ static void read_cache_sizes(BlockDriverState *bs, QemuOpts *opts,

     BDRVQcow2State *s = bs->opaque;

     uint64_t combined_cache_size;

     bool l2_cache_size_set, refcount_cache_size_set, combined_cache_size_set;

+    int min_refcount_cache = MIN_REFCOUNT_CACHE_SIZE * s->cluster_size;

     combined_cache_size_set = qemu_opt_get(opts, QCOW2_OPT_CACHE_SIZE);

     l2_cache_size_set = qemu_opt_get(opts, QCOW2_OPT_L2_CACHE_SIZE);

@@ -811,8 +812,6 @@ static void read_cache_sizes(BlockDriverState *bs, QemuOpts *opts,

         } else {

             uint64_t virtual_disk_size = bs->total_sectors * BDRV_SECTOR_SIZE;

             uint64_t max_l2_cache = virtual_disk_size / (s->cluster_size / 8);

-            uint64_t min_refcount_cache =

-                (uint64_t) MIN_REFCOUNT_CACHE_SIZE * s->cluster_size;

             /* Assign as much memory as possible to the L2 cache, and

              * use the remainder for the refcount cache */

@@ -832,7 +831,7 @@ static void read_cache_sizes(BlockDriverState *bs, QemuOpts *opts,

                                  * s->cluster_size);

         }

         if (!refcount_cache_size_set) {

-            *refcount_cache_size = MIN_REFCOUNT_CACHE_SIZE * s->cluster_size;

+            *refcount_cache_size = min_refcount_cache;

         }

     }

-- 

1.8.3.1