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Date: Sat, 23 Jun 2018 23:21:07 +0100
From: Al Viro <viro@...IV.linux.org.uk>
To: David Miller <davem@...emloft.net>
Cc: pmoore@...hat.com, netdev@...r.kernel.org, selinux@...ho.nsa.gov,
linux-security-module@...r.kernel.org
Subject: Re: [PATCH] ipv6: avoid copy_from_user() via
ipv6_renew_options_kern()
On Sat, Jun 23, 2018 at 10:26:27PM +0100, Al Viro wrote:
> On Sat, Jun 23, 2018 at 10:57:06AM +0900, David Miller wrote:
> > From: Paul Moore <pmoore@...hat.com>
> > Date: Fri, 22 Jun 2018 17:18:20 -0400
> >
> > > - const mm_segment_t old_fs = get_fs();
> > > -
> > > - set_fs(KERNEL_DS);
> > > - ret_val = ipv6_renew_options(sk, opt, newtype,
> > > - (struct ipv6_opt_hdr __user *)newopt,
> > > - newoptlen);
> > > - set_fs(old_fs);
> >
> > So is it really the case that the traditional construct:
> >
> > set_fs(KERNEL_DS);
> > ... copy_{from,to}_user(...);
> > set_fs(old_fs);
> >
> > is no longer allowed?
>
> s/no longer allowed/best avoided/, but IMO in this case the replacement is
> too ugly to live ;-/
BTW, I wonder if the life would be simpler with do_ipv6_setsockopt() doing
the copy-in and verifying ipv6_optlen(*hdr) <= newoptlen; that would've
simplified ipv6_renew_option{,s}() quite a bit and completely eliminated
ipv6_renew_options_kern()...
Incidentally, is copying the entire value in case newoptlen > ipv6_optlen(...)
the right thing? After all, the next update in any of those options will
quietly lose everything past ipv6_optlen(...), wouldn't it?
IOW, how about the following (completely untested):
diff --git a/include/net/ipv6.h b/include/net/ipv6.h
index 16475c269749..d02881e4ad1f 100644
--- a/include/net/ipv6.h
+++ b/include/net/ipv6.h
@@ -355,14 +355,7 @@ struct ipv6_txoptions *ipv6_dup_options(struct sock *sk,
struct ipv6_txoptions *ipv6_renew_options(struct sock *sk,
struct ipv6_txoptions *opt,
int newtype,
- struct ipv6_opt_hdr __user *newopt,
- int newoptlen);
-struct ipv6_txoptions *
-ipv6_renew_options_kern(struct sock *sk,
- struct ipv6_txoptions *opt,
- int newtype,
- struct ipv6_opt_hdr *newopt,
- int newoptlen);
+ struct ipv6_opt_hdr *newopt);
struct ipv6_txoptions *ipv6_fixup_options(struct ipv6_txoptions *opt_space,
struct ipv6_txoptions *opt);
diff --git a/net/ipv6/calipso.c b/net/ipv6/calipso.c
index 1323b9679cf7..1c0bb9fb76e6 100644
--- a/net/ipv6/calipso.c
+++ b/net/ipv6/calipso.c
@@ -799,8 +799,7 @@ static int calipso_opt_update(struct sock *sk, struct ipv6_opt_hdr *hop)
{
struct ipv6_txoptions *old = txopt_get(inet6_sk(sk)), *txopts;
- txopts = ipv6_renew_options_kern(sk, old, IPV6_HOPOPTS,
- hop, hop ? ipv6_optlen(hop) : 0);
+ txopts = ipv6_renew_options(sk, old, IPV6_HOPOPTS, hop);
txopt_put(old);
if (IS_ERR(txopts))
return PTR_ERR(txopts);
@@ -1222,8 +1221,7 @@ static int calipso_req_setattr(struct request_sock *req,
if (IS_ERR(new))
return PTR_ERR(new);
- txopts = ipv6_renew_options_kern(sk, req_inet->ipv6_opt, IPV6_HOPOPTS,
- new, new ? ipv6_optlen(new) : 0);
+ txopts = ipv6_renew_options(sk, req_inet->ipv6_opt, IPV6_HOPOPTS, new);
kfree(new);
@@ -1260,8 +1258,7 @@ static void calipso_req_delattr(struct request_sock *req)
if (calipso_opt_del(req_inet->ipv6_opt->hopopt, &new))
return; /* Nothing to do */
- txopts = ipv6_renew_options_kern(sk, req_inet->ipv6_opt, IPV6_HOPOPTS,
- new, new ? ipv6_optlen(new) : 0);
+ txopts = ipv6_renew_options(sk, req_inet->ipv6_opt, IPV6_HOPOPTS, new);
if (!IS_ERR(txopts)) {
txopts = xchg(&req_inet->ipv6_opt, txopts);
diff --git a/net/ipv6/exthdrs.c b/net/ipv6/exthdrs.c
index 5bc2bf3733ab..4b6915eedfc3 100644
--- a/net/ipv6/exthdrs.c
+++ b/net/ipv6/exthdrs.c
@@ -1015,29 +1015,15 @@ ipv6_dup_options(struct sock *sk, struct ipv6_txoptions *opt)
}
EXPORT_SYMBOL_GPL(ipv6_dup_options);
-static int ipv6_renew_option(void *ohdr,
- struct ipv6_opt_hdr __user *newopt, int newoptlen,
- int inherit,
+static void ipv6_renew_option(struct ipv6_opt_hdr *opt,
struct ipv6_opt_hdr **hdr,
char **p)
{
- if (inherit) {
- if (ohdr) {
- memcpy(*p, ohdr, ipv6_optlen((struct ipv6_opt_hdr *)ohdr));
- *hdr = (struct ipv6_opt_hdr *)*p;
- *p += CMSG_ALIGN(ipv6_optlen(*hdr));
- }
- } else {
- if (newopt) {
- if (copy_from_user(*p, newopt, newoptlen))
- return -EFAULT;
- *hdr = (struct ipv6_opt_hdr *)*p;
- if (ipv6_optlen(*hdr) > newoptlen)
- return -EINVAL;
- *p += CMSG_ALIGN(newoptlen);
- }
+ if (opt) {
+ memcpy(*p, opt, ipv6_optlen(opt));
+ *hdr = (struct ipv6_opt_hdr *)*p;
+ *p += CMSG_ALIGN(ipv6_optlen(*hdr));
}
- return 0;
}
/**
@@ -1063,13 +1049,11 @@ static int ipv6_renew_option(void *ohdr,
*/
struct ipv6_txoptions *
ipv6_renew_options(struct sock *sk, struct ipv6_txoptions *opt,
- int newtype,
- struct ipv6_opt_hdr __user *newopt, int newoptlen)
+ int newtype, struct ipv6_opt_hdr *newopt)
{
int tot_len = 0;
char *p;
struct ipv6_txoptions *opt2;
- int err;
if (opt) {
if (newtype != IPV6_HOPOPTS && opt->hopopt)
@@ -1082,8 +1066,8 @@ ipv6_renew_options(struct sock *sk, struct ipv6_txoptions *opt,
tot_len += CMSG_ALIGN(ipv6_optlen(opt->dst1opt));
}
- if (newopt && newoptlen)
- tot_len += CMSG_ALIGN(newoptlen);
+ if (newopt)
+ tot_len += CMSG_ALIGN(ipv6_optlen(newopt));
if (!tot_len)
return NULL;
@@ -1098,67 +1082,25 @@ ipv6_renew_options(struct sock *sk, struct ipv6_txoptions *opt,
opt2->tot_len = tot_len;
p = (char *)(opt2 + 1);
- err = ipv6_renew_option(opt ? opt->hopopt : NULL, newopt, newoptlen,
- newtype != IPV6_HOPOPTS,
- &opt2->hopopt, &p);
- if (err)
- goto out;
-
- err = ipv6_renew_option(opt ? opt->dst0opt : NULL, newopt, newoptlen,
- newtype != IPV6_RTHDRDSTOPTS,
- &opt2->dst0opt, &p);
- if (err)
- goto out;
-
- err = ipv6_renew_option(opt ? opt->srcrt : NULL, newopt, newoptlen,
- newtype != IPV6_RTHDR,
- (struct ipv6_opt_hdr **)&opt2->srcrt, &p);
- if (err)
- goto out;
-
- err = ipv6_renew_option(opt ? opt->dst1opt : NULL, newopt, newoptlen,
- newtype != IPV6_DSTOPTS,
- &opt2->dst1opt, &p);
- if (err)
- goto out;
-
+ ipv6_renew_option(newtype == IPV6_HOPOPTS ? newopt :
+ opt ? opt->hopopt : NULL,
+ &opt2->hopopt, &p);
+
+ ipv6_renew_option(newtype == IPV6_RTHDRDSTOPTS ? newopt :
+ opt ? opt->dst0opt : NULL,
+ &opt2->dst0opt, &p);
+ ipv6_renew_option(newtype == IPV6_RTHDR ? newopt :
+ opt ? (struct ipv6_opt_hdr *)opt->srcrt : NULL,
+ (struct ipv6_opt_hdr **)&opt2->srcrt, &p);
+ ipv6_renew_option(newtype == IPV6_DSTOPTS ? newopt :
+ opt ? opt->dst1opt : NULL,
+ &opt2->dst1opt, &p);
opt2->opt_nflen = (opt2->hopopt ? ipv6_optlen(opt2->hopopt) : 0) +
(opt2->dst0opt ? ipv6_optlen(opt2->dst0opt) : 0) +
(opt2->srcrt ? ipv6_optlen(opt2->srcrt) : 0);
opt2->opt_flen = (opt2->dst1opt ? ipv6_optlen(opt2->dst1opt) : 0);
return opt2;
-out:
- sock_kfree_s(sk, opt2, opt2->tot_len);
- return ERR_PTR(err);
-}
-
-/**
- * ipv6_renew_options_kern - replace a specific ext hdr with a new one.
- *
- * @sk: sock from which to allocate memory
- * @opt: original options
- * @newtype: option type to replace in @opt
- * @newopt: new option of type @newtype to replace (kernel-mem)
- * @newoptlen: length of @newopt
- *
- * See ipv6_renew_options(). The difference is that @newopt is
- * kernel memory, rather than user memory.
- */
-struct ipv6_txoptions *
-ipv6_renew_options_kern(struct sock *sk, struct ipv6_txoptions *opt,
- int newtype, struct ipv6_opt_hdr *newopt,
- int newoptlen)
-{
- struct ipv6_txoptions *ret_val;
- const mm_segment_t old_fs = get_fs();
-
- set_fs(KERNEL_DS);
- ret_val = ipv6_renew_options(sk, opt, newtype,
- (struct ipv6_opt_hdr __user *)newopt,
- newoptlen);
- set_fs(old_fs);
- return ret_val;
}
struct ipv6_txoptions *ipv6_fixup_options(struct ipv6_txoptions *opt_space,
diff --git a/net/ipv6/ipv6_sockglue.c b/net/ipv6/ipv6_sockglue.c
index 4d780c7f0130..b69ba18e0138 100644
--- a/net/ipv6/ipv6_sockglue.c
+++ b/net/ipv6/ipv6_sockglue.c
@@ -398,6 +398,12 @@ static int do_ipv6_setsockopt(struct sock *sk, int level, int optname,
case IPV6_DSTOPTS:
{
struct ipv6_txoptions *opt;
+ struct ipv6_opt_hdr *new = NULL;
+
+ /* hop-by-hop / destination options are privileged option */
+ retv = -EPERM;
+ if (optname != IPV6_RTHDR && !ns_capable(net->user_ns, CAP_NET_RAW))
+ break;
/* remove any sticky options header with a zero option
* length, per RFC3542.
@@ -409,17 +415,23 @@ static int do_ipv6_setsockopt(struct sock *sk, int level, int optname,
else if (optlen < sizeof(struct ipv6_opt_hdr) ||
optlen & 0x7 || optlen > 8 * 255)
goto e_inval;
-
- /* hop-by-hop / destination options are privileged option */
- retv = -EPERM;
- if (optname != IPV6_RTHDR && !ns_capable(net->user_ns, CAP_NET_RAW))
- break;
+ else {
+ new = kmemdup(optval, optlen, GFP_USER);
+ if (IS_ERR(new)) {
+ retv = PTR_ERR(new);
+ break;
+ }
+ if (unlikely(ipv6_optlen(new) > optlen)) {
+ kfree(new);
+ retv = -EINVAL;
+ break;
+ }
+ }
opt = rcu_dereference_protected(np->opt,
lockdep_sock_is_held(sk));
- opt = ipv6_renew_options(sk, opt, optname,
- (struct ipv6_opt_hdr __user *)optval,
- optlen);
+ opt = ipv6_renew_options(sk, opt, optname, new);
+ kfree(new);
if (IS_ERR(opt)) {
retv = PTR_ERR(opt);
break;
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