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Re: [Qemu-devel] [PATCH] slirp: Use lduw_be_p in slirp_input
From: |
Philippe Mathieu-Daudé |
Subject: |
Re: [Qemu-devel] [PATCH] slirp: Use lduw_be_p in slirp_input |
Date: |
Thu, 17 Jan 2019 14:16:16 +0100 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.4.0 |
On 1/17/19 12:50 AM, Samuel Thibault wrote:
> Hello,
>
> Richard Henderson, le mer. 26 déc. 2018 14:42:54 +1100, a ecrit:
>> The pointer may be unaligned, so we must use our routines for that.
>> At the same time, we might as well use the big-endian version
>> instead of ntohs.
>>
>> This fixes sparc64 host SIGBUS during pxe boot.
>
> I'm not at ease with applying this, when Marc-André is trying to make
> slirp an external library... I'd rather apply the change below, could
> somebody review it?
>
> Samuel
>
>
> slirp: Avoid unaligned 16bit memory access
>
> pkt parameter may be unaligned, so we must access it byte-wise.
>
> This fixes sparc64 host SIGBUS during pxe boot.
>
> Signed-off-by: Samuel Thibault <address@hidden>
>
> diff --git a/slirp/slirp.c b/slirp/slirp.c
> index ab2fc4eb8b..0e41d5aedf 100644
> --- a/slirp/slirp.c
> +++ b/slirp/slirp.c
> @@ -851,7 +851,7 @@ void slirp_input(Slirp *slirp, const uint8_t *pkt, int
> pkt_len)
> if (pkt_len < ETH_HLEN)
> return;
>
> - proto = ntohs(*(uint16_t *)(pkt + 12));
> + proto = (((uint16_t) pkt[12]) << 8) + pkt[13];
> switch(proto) {
> case ETH_P_ARP:
> arp_input(slirp, pkt, pkt_len);
What about using memcpy?
-- >8 --
@@ -846,12 +846,13 @@ static void arp_input(Slirp *slirp, const uint8_t
*pkt, int pkt_len)
void slirp_input(Slirp *slirp, const uint8_t *pkt, int pkt_len)
{
struct mbuf *m;
- int proto;
+ uint16_t proto;
if (pkt_len < ETH_HLEN)
return;
- proto = ntohs(*(uint16_t *)(pkt + 12));
+ memcpy(&proto, pkt + 12, sizeof(proto)); /* Avoid unaligned 16bit
access */
+ proto = ntohs(proto);
switch(proto) {
case ETH_P_ARP:
arp_input(slirp, pkt, pkt_len);
---