File 0004-quic-Avoid-possible-buffer-overflow-in-find_bucket.patch of Package spice.19892

From cf4fe0dba84d70acadf5a5a5ca8acef53c36df1d Mon Sep 17 00:00:00 2001
From: Frediano Ziglio <freddy77@gmail.com>
Date: Thu, 30 Apr 2020 10:19:09 +0100
Subject: [PATCH 4/4] quic: Avoid possible buffer overflow in find_bucket

Proved by fuzzing the code.

Signed-off-by: Frediano Ziglio <freddy77@gmail.com>
Acked-by: Uri Lublin <uril@redhat.com>
Signed-off-by: Bruce Rogers <brogers@suse.com>
---
 spice-common/common/quic_family_tmpl.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/spice-common/common/quic_family_tmpl.c b/spice-common/common/quic_family_tmpl.c
index 70fe758..00edf8e 100644
--- a/spice-common/common/quic_family_tmpl.c
+++ b/spice-common/common/quic_family_tmpl.c
@@ -107,7 +107,12 @@ static s_bucket *FNAME(find_bucket)(Channel *channel, const unsigned int val)
 {
     spice_assert(val < (0x1U << BPC));
 
-    return channel->_buckets_ptrs[val];
+    /* The and (&) here is to avoid buffer overflows in case of garbage or malicious
+     * attempts. Is much faster then using comparisons and save us from such situations.
+     * Note that on normal build the check above won't be compiled as this code path
+     * is pretty hot and would cause speed regressions.
+     */
+    return channel->_buckets_ptrs[val & ((1U << BPC) - 1)];
 }
 
 #undef FNAME
-- 
2.28.0