Re: [RFC 8/8] ip_frag: fix gcc-12 warnings

[Konstantin Ananyev]

07/06/2022 18:17, Stephen Hemminger пишет:

The function rte_memcpy can derference past source buffer which
will cause array out of bounds warnings. But there is no good reason
to use rte_memcpy instead of memcpy in this code. Memcpy is just
as fast for these small inputs, and compiler will optimize.

AFAIK, rte_memcpy() will outperform memcpy() when _size_ parameter
is a variable. Unfortunately that's exactly the case here.
So not sure it is a good change, at least without extensive perf testing.
BTW, if rte_memcpy() really access src buffer beyond it's boundaries,
I think that's definitely a bug that needs to be fixed.

Signed-off-by: Stephen Hemminger <step...@networkplumber.org>
---
  lib/ip_frag/rte_ipv4_fragmentation.c | 7 +++----
  1 file changed, 3 insertions(+), 4 deletions(-)

diff --git a/lib/ip_frag/rte_ipv4_fragmentation.c 
b/lib/ip_frag/rte_ipv4_fragmentation.c
index a19f6fda6408..27a8ad224dec 100644
--- a/lib/ip_frag/rte_ipv4_fragmentation.c
+++ b/lib/ip_frag/rte_ipv4_fragmentation.c
@@ -5,7 +5,6 @@
  #include <stddef.h>
  #include <errno.h>

-#include <rte_memcpy.h>

  #include <rte_ether.h>

#include "ip_frag_common.h"

@@ -26,7 +25,7 @@ static inline void __fill_ipv4hdr_frag(struct rte_ipv4_hdr 
*dst,
                const struct rte_ipv4_hdr *src, uint16_t header_len,
                uint16_t len, uint16_t fofs, uint16_t dofs, uint32_t mf)
  {
-       rte_memcpy(dst, src, header_len);
+       memcpy(dst, src, header_len);
        fofs = (uint16_t)(fofs + (dofs >> RTE_IPV4_HDR_FO_SHIFT));
        fofs = (uint16_t)(fofs | mf << RTE_IPV4_HDR_MF_SHIFT);
        dst->fragment_offset = rte_cpu_to_be_16(fofs);
@@ -48,7 +47,7 @@ static inline uint16_t __create_ipopt_frag_hdr(uint8_t *iph,
        struct rte_ipv4_hdr *iph_opt = (struct rte_ipv4_hdr *)ipopt_frag_hdr;

ipopt_len = 0;

-       rte_memcpy(ipopt_frag_hdr, iph, sizeof(struct rte_ipv4_hdr));
+       memcpy(ipopt_frag_hdr, iph, sizeof(struct rte_ipv4_hdr));
        ipopt_frag_hdr += sizeof(struct rte_ipv4_hdr);

uint8_t *p_opt = iph + sizeof(struct rte_ipv4_hdr);

@@ -65,7 +64,7 @@ static inline uint16_t __create_ipopt_frag_hdr(uint8_t *iph,
                        break;

if (RTE_IPV4_HDR_OPT_COPIED(*p_opt)) {

-                       rte_memcpy(ipopt_frag_hdr + ipopt_len,
+                       memcpy(ipopt_frag_hdr + ipopt_len,
                                p_opt, p_opt[1]);
                        ipopt_len += p_opt[1];
                }