xfrm: esp: avoid in-place decrypt on shared skb frags

commit f4c50a4034e62ab75f1d5cdd191dd5f9c77fdff4 upstream.

MSG_SPLICE_PAGES can attach pages from a pipe directly to an skb. TCP
marks such skbs with SKBFL_SHARED_FRAG after skb_splice_from_iter(),
so later paths that may modify packet data can first make a private
copy. The IPv4/IPv6 datagram append paths did not set this flag when
splicing pages into UDP skbs.

That leaves an ESP-in-UDP packet made from shared pipe pages looking
like an ordinary uncloned nonlinear skb. ESP input then takes the no-COW
fast path for uncloned skbs without a frag_list and decrypts in place
over data that is not owned privately by the skb.

Mark IPv4/IPv6 datagram splice frags with SKBFL_SHARED_FRAG, matching
TCP. Also make ESP input fall back to skb_cow_data() when the flag is
present, so ESP does not decrypt externally backed frags in place.
Private nonlinear skb frags still use the existing fast path.

This intentionally does not change ESP output. In esp_output_head(),
the path that appends the ESP trailer to existing skb tailroom without
calling skb_cow_data() is not reachable for nonlinear skbs:
skb_tailroom() returns zero when skb->data_len is nonzero, while ESP
tailen is positive. Thus ESP output will either use the separate
destination-frag path or fall back to skb_cow_data().

Fixes: cac2661c53f3 ("esp4: Avoid skb_cow_data whenever possible")
Fixes: 03e2a30f6a27 ("esp6: Avoid skb_cow_data whenever possible")
Fixes: 7da0dde68486 ("ip, udp: Support MSG_SPLICE_PAGES")
Fixes: 6d8192bd69bb ("ip6, udp6: Support MSG_SPLICE_PAGES")
Reported-by: Hyunwoo Kim <imv4bel@gmail.com>
Reported-by: Kuan-Ting Chen <h3xrabbit@gmail.com>
Tested-by: Hyunwoo Kim <imv4bel@gmail.com>
Cc: stable@vger.kernel.org
Signed-off-by: Kuan-Ting Chen <h3xrabbit@gmail.com>
Signed-off-by: Steffen Klassert <steffen.klassert@secunet.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/net/ipv4/esp4.c b/net/ipv4/esp4.c
index 6dfc0bcdef65429b03e8fd117a4ad15558d9ca79..6a5febbdbee493958427c70795880a3a8fffc1e3 100644 (file)
--- a/net/ipv4/esp4.c
+++ b/net/ipv4/esp4.c
@@ -873,7 +873,8 @@ static int esp_input(struct xfrm_state *x, struct sk_buff *skb)
                        nfrags = 1;
 
                        goto skip_cow;
-               } else if (!skb_has_frag_list(skb)) {
+               } else if (!skb_has_frag_list(skb) &&
+                          !skb_has_shared_frag(skb)) {
                        nfrags = skb_shinfo(skb)->nr_frags;
                        nfrags++;
 

diff --git a/net/ipv4/ip_output.c b/net/ipv4/ip_output.c
index e4790cc7b5c2ec7d6893d4141ca250ec05a4a2f5..5bcd73cbdb41c0d402c025cc449a9f84fd2833e0 100644 (file)
--- a/net/ipv4/ip_output.c
+++ b/net/ipv4/ip_output.c
@@ -1233,6 +1233,8 @@ alloc_new_skb:
                        if (err < 0)
                                goto error;
                        copy = err;
+                       if (!(flags & MSG_NO_SHARED_FRAGS))
+                               skb_shinfo(skb)->flags |= SKBFL_SHARED_FRAG;
                        wmem_alloc_delta += copy;
                } else if (!zc) {
                        int i = skb_shinfo(skb)->nr_frags;

diff --git a/net/ipv6/esp6.c b/net/ipv6/esp6.c
index 9f75313734f8cd5c9ef419990a4e846cee2d23cf..9c06c5a1419dc4cae33a3aef22bf1ea835e91203 100644 (file)
--- a/net/ipv6/esp6.c
+++ b/net/ipv6/esp6.c
@@ -915,7 +915,8 @@ static int esp6_input(struct xfrm_state *x, struct sk_buff *skb)
                        nfrags = 1;
 
                        goto skip_cow;
-               } else if (!skb_has_frag_list(skb)) {
+               } else if (!skb_has_frag_list(skb) &&
+                          !skb_has_shared_frag(skb)) {
                        nfrags = skb_shinfo(skb)->nr_frags;
                        nfrags++;
 

diff --git a/net/ipv6/ip6_output.c b/net/ipv6/ip6_output.c
index 8e2a6b28cea7ae69099859b337c9044caf99e631..3f14e363c96e205cc82e3ec2ba102a8531d52990 100644 (file)
--- a/net/ipv6/ip6_output.c
+++ b/net/ipv6/ip6_output.c
@@ -1765,6 +1765,8 @@ alloc_new_skb:
                        if (err < 0)
                                goto error;
                        copy = err;
+                       if (!(flags & MSG_NO_SHARED_FRAGS))
+                               skb_shinfo(skb)->flags |= SKBFL_SHARED_FRAG;
                        wmem_alloc_delta += copy;
                } else if (!zc) {
                        int i = skb_shinfo(skb)->nr_frags;