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spice/SOURCES/0004-quic-Avoid-possible-bu...

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From 57c6e6b00247ad289a27648213d7ad2306fe3931 Mon Sep 17 00:00:00 2001
From: Frediano Ziglio <freddy77@gmail.com>
Date: Thu, 30 Apr 2020 10:19:09 +0100
Subject: [PATCH spice-common 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>
---
common/quic_family_tmpl.c | 7 ++++++-
1 file changed, 6 insertions(+), 1 deletion(-)
diff --git a/subprojects/spice-common/common/quic_family_tmpl.c b/subprojects/spice-common/common/quic_family_tmpl.c
index 8a5f7d2..6cc051b 100644
--- a/subprojects/spice-common/common/quic_family_tmpl.c
+++ b/subprojects/spice-common/common/quic_family_tmpl.c
@@ -103,7 +103,12 @@ 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
--
2.25.4