> On Sep 8, 2021, at 5:26 PM, Bruce Fields <bfields@xxxxxxxxxxxx> wrote:
>
> On Tue, Sep 07, 2021 at 03:00:23PM +0000, Chuck Lever III wrote:
>> We have IPV6_SCOPE_ID_LEN as a maximum size of the scope ID,
>> and it's not a big value. As long as boundary checking is made
>> to be sufficient, then a stack residency for the device name
>> should be safe.
>
> Something like this? (Or are you making a patch?
I thought Jeff was going to handle it? More below.
> I'm not even sure how to test.)
>
> --b.
>
> diff --git a/net/sunrpc/addr.c b/net/sunrpc/addr.c
> index 6e4dbd577a39..d435bffc6199 100644
> --- a/net/sunrpc/addr.c
> +++ b/net/sunrpc/addr.c
> @@ -162,8 +162,10 @@ static int rpc_parse_scope_id(struct net *net, const char *buf,
> const size_t buflen, const char *delim,
> struct sockaddr_in6 *sin6)
> {
> - char *p;
> + char p[IPV6_SCOPE_ID_LEN + 1];
> size_t len;
> + u32 scope_id = 0;
> + struct net_device *dev;
>
> if ((buf + buflen) == delim)
> return 1;
> @@ -175,29 +177,23 @@ static int rpc_parse_scope_id(struct net *net, const char *buf,
> return 0;
>
> len = (buf + buflen) - delim - 1;
> - p = kmemdup_nul(delim + 1, len, GFP_KERNEL);
> - if (p) {
> - u32 scope_id = 0;
> - struct net_device *dev;
> -
> - dev = dev_get_by_name(net, p);
> - if (dev != NULL) {
> - scope_id = dev->ifindex;
> - dev_put(dev);
> - } else {
> - if (kstrtou32(p, 10, &scope_id) != 0) {
> - kfree(p);
> - return 0;
> - }
> - }
> -
> - kfree(p);
> -
> - sin6->sin6_scope_id = scope_id;
> - return 1;
> + if (len > IPV6_SCOPE_ID_LEN)
> + return 0;
> +
> + memcpy(p, delim + 1, len);
> + p[len] = 0;
If I recall correctly, Linus prefers us to use the str*()
functions instead of raw memcpy() in cases like this.
> +
> + dev = dev_get_by_name(net, p);
> + if (dev != NULL) {
> + scope_id = dev->ifindex;
> + dev_put(dev);
> + } else {
> + if (kstrtou32(p, 10, &scope_id) != 0)
> + return 0;
> }
>
> - return 0;
> + sin6->sin6_scope_id = scope_id;
> + return 1;
> }
>
> static size_t rpc_pton6(struct net *net, const char *buf, const size_t buflen,
--
Chuck Lever
