inet: add RCU protection to inet->opt
We lack proper synchronization to manipulate inet->opt ip_options
Problem is ip_make_skb() calls ip_setup_cork() and
ip_setup_cork() possibly makes a copy of ipc->opt (struct ip_options),
without any protection against another thread manipulating inet->opt.
Another thread can change inet->opt pointer and free old one under us.
Use RCU to protect inet->opt (changed to inet->inet_opt).
Instead of handling atomic refcounts, just copy ip_options when
necessary, to avoid cache line dirtying.
We cant insert an rcu_head in struct ip_options since its included in
skb->cb[], so this patch is large because I had to introduce a new
ip_options_rcu structure.
Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
Cc: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/ipv4/raw.c b/net/ipv4/raw.c
index abf14db..a8659e0 100644
--- a/net/ipv4/raw.c
+++ b/net/ipv4/raw.c
@@ -460,6 +460,7 @@
__be32 saddr;
u8 tos;
int err;
+ struct ip_options_data opt_copy;
err = -EMSGSIZE;
if (len > 0xFFFF)
@@ -520,8 +521,18 @@
saddr = ipc.addr;
ipc.addr = daddr;
- if (!ipc.opt)
- ipc.opt = inet->opt;
+ if (!ipc.opt) {
+ struct ip_options_rcu *inet_opt;
+
+ rcu_read_lock();
+ inet_opt = rcu_dereference(inet->inet_opt);
+ if (inet_opt) {
+ memcpy(&opt_copy, inet_opt,
+ sizeof(*inet_opt) + inet_opt->opt.optlen);
+ ipc.opt = &opt_copy.opt;
+ }
+ rcu_read_unlock();
+ }
if (ipc.opt) {
err = -EINVAL;
@@ -530,10 +541,10 @@
*/
if (inet->hdrincl)
goto done;
- if (ipc.opt->srr) {
+ if (ipc.opt->opt.srr) {
if (!daddr)
goto done;
- daddr = ipc.opt->faddr;
+ daddr = ipc.opt->opt.faddr;
}
}
tos = RT_CONN_FLAGS(sk);