From 57c6e6b00247ad289a27648213d7ad2306fe3931 Mon Sep 17 00:00:00 2001 From: Frediano Ziglio 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 Acked-by: Uri Lublin --- 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