[PATCH] net: fix signed shift overflow in IPv6 phdr cksum

[Aleksandr Khromov <haa@amicon.ru>]

In rte_ipv6_phdr_cksum() the next header field, a uint8_t, is promoted to
a signed int before the left shift by 24. For protocol values >= 128
(for example IPPROTO_SCTP), proto << 24 does not fit in int, which is
undefined behaviour (signed left shift overflow) reported by UBSan:

  rte_ip6.h: runtime error: left shift of 132 by 24 places cannot be
  represented in type 'int'

Cast the operand to uint32_t before the shift so it is performed in
unsigned arithmetic. The resulting value is unchanged on two's
complement platforms. The same idiom is already used in RTE_IPV4().

Fixes: 6006818cfb26 ("net: new checksum functions")
Cc: stable@dpdk.org
Signed-off-by: Aleksandr Khromov <haa@amicon.ru>
---
 .mailmap          | 1 +
 lib/net/rte_ip6.h | 2 +-
 2 files changed, 2 insertions(+), 1 deletion(-)

diff --git a/.mailmap b/.mailmap
index 9e45cdce8f..2d55627dc5 100644
--- a/.mailmap
+++ b/.mailmap
@@ -46,6 +46,7 @@ Alan Liu <zaoxingliu@gmail.com>
 Alan Winkowski <walan@marvell.com>
 Alejandro Lucero <alejandro.lucero@netronome.com>
 Aleksander Gajewski <aleksanderx.gajewski@intel.com>
+Aleksandr Khromov <haa@amicon.ru>
 Aleksandr Loktionov <aleksandr.loktionov@intel.com>
 Aleksandr Miloshenko <a.miloshenko@f5.com>
 Aleksey Baulin <aleksey.baulin@gmail.com>
diff --git a/lib/net/rte_ip6.h b/lib/net/rte_ip6.h
index d1abf1f5d5..14e0101c14 100644
--- a/lib/net/rte_ip6.h
+++ b/lib/net/rte_ip6.h
@@ -566,7 +566,7 @@ rte_ipv6_phdr_cksum(const struct rte_ipv6_hdr *ipv6_hdr, uint64_t ol_flags)
 		rte_be32_t proto; /* L4 protocol - top 3 bytes must be zero */
 	} psd_hdr;
 
-	psd_hdr.proto = (uint32_t)(ipv6_hdr->proto << 24);
+	psd_hdr.proto = (uint32_t)ipv6_hdr->proto << 24;
 	if (ol_flags & (RTE_MBUF_F_TX_TCP_SEG | RTE_MBUF_F_TX_UDP_SEG))
 		psd_hdr.len = 0;
 	else
-- 
2.48.1