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

[Konstantin Ananyev <konstantin.v.ananyev@yandex.ru>]

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 <stephen@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];
>   		}