esp: fix page frag reference leak on skb_to_sgvec failure

In esp_output_tail(), when esp->inplace is false, the old skb page frags
are replaced with a new page from the xfrm page_frag cache The source
scatterlist (sg) is built from the old frags before the replacement, and
esp_ssg_unref() is responsible for releasing the old page references
after the crypto operation completes

However, if the second skb_to_sgvec() call (which builds the destination
scatterlist from the new page) fails, the code jumps to error_free which
only calls kfree(tmp). The old page frag references captured in the
source scatterlist are never released:

  1 sg[] is built from old frags via skb_to_sgvec() (no extra get_page)
  2 nr_frags is set to 1 and frag[0] is replaced with the new page
  3 Second skb_to_sgvec() fails -> goto error_free

Fix this by adding a bool parameter to esp_ssg_unref() that, when true,
unconditionally unrefs the source scatterlist frags. Since req->src is
not yet initialized by aead_request_set_crypt() at the point of the
error, the source scatterlist is obtained directly via esp_req_sg()
Existing callers pass false to preserve the original behavior

The same issue exists in both esp4 and esp6 as the code is identical

Fixes: cac2661c53f3 ("esp4: Avoid skb_cow_data whenever possible")
Fixes: 03e2a30f6a27 ("esp6: Avoid skb_cow_data whenever possible")
Signed-off-by: Alessandro Schino <7991aleschino@gmail.com>
Signed-off-by: Steffen Klassert <steffen.klassert@secunet.com>

diff --git a/net/ipv4/esp4.c b/net/ipv4/esp4.c
index 513c8215c947f109a5a6850feb317b6d988fe445..dfc81ee969ae03337fbe9f89a976d3d0ace224f4 100644 (file)
--- a/net/ipv4/esp4.c
+++ b/net/ipv4/esp4.c
@@ -96,7 +96,7 @@ static inline struct scatterlist *esp_req_sg(struct crypto_aead *aead,
                             __alignof__(struct scatterlist));
 }
 
-static void esp_ssg_unref(struct xfrm_state *x, void *tmp, struct sk_buff *skb)
+static void esp_ssg_unref(struct xfrm_state *x, void *tmp, struct sk_buff *skb, bool already_unref)
 {
        struct crypto_aead *aead = x->data;
        int extralen = 0;
@@ -113,10 +113,13 @@ static void esp_ssg_unref(struct xfrm_state *x, void *tmp, struct sk_buff *skb)
        /* Unref skb_frag_pages in the src scatterlist if necessary.
         * Skip the first sg which comes from skb->data.
         */
-       if (req->src != req->dst)
-               for (sg = sg_next(req->src); sg; sg = sg_next(sg))
+       if (already_unref || req->src != req->dst) {
+               struct scatterlist *src = already_unref ? esp_req_sg(aead, req) : req->src;
+
+               for (sg = sg_next(src); sg; sg = sg_next(sg))
                        skb_page_unref(page_to_netmem(sg_page(sg)),
                                       skb->pp_recycle);
+       }
 }
 
 #ifdef CONFIG_INET_ESPINTCP
@@ -220,7 +223,7 @@ static void esp_output_done(void *data, int err)
        }
 
        tmp = ESP_SKB_CB(skb)->tmp;
-       esp_ssg_unref(x, tmp, skb);
+       esp_ssg_unref(x, tmp, skb, false);
        kfree(tmp);
 
        if (xo && (xo->flags & XFRM_DEV_RESUME)) {
@@ -569,8 +572,10 @@ int esp_output_tail(struct xfrm_state *x, struct sk_buff *skb, struct esp_info *
                err = skb_to_sgvec(skb, dsg,
                                   (unsigned char *)esph - skb->data,
                                   assoclen + ivlen + esp->clen + alen);
-               if (unlikely(err < 0))
+               if (unlikely(err < 0)) {
+                       esp_ssg_unref(x, tmp, skb, true);
                        goto error_free;
+               }
        }
 
        if ((x->props.flags & XFRM_STATE_ESN))
@@ -602,7 +607,7 @@ int esp_output_tail(struct xfrm_state *x, struct sk_buff *skb, struct esp_info *
        }
 
        if (sg != dsg)
-               esp_ssg_unref(x, tmp, skb);
+               esp_ssg_unref(x, tmp, skb, false);
 
        if (!err && x->encap && x->encap->encap_type == TCP_ENCAP_ESPINTCP)
                err = esp_output_tail_tcp(x, skb);

diff --git a/net/ipv6/esp6.c b/net/ipv6/esp6.c
index 57481e423e59e6c88a3c972d1d9bfd3bf02b08b6..296b57926abb985a5761d1f90e678f2956df5ea9 100644 (file)
--- a/net/ipv6/esp6.c
+++ b/net/ipv6/esp6.c
@@ -113,7 +113,7 @@ static inline struct scatterlist *esp_req_sg(struct crypto_aead *aead,
                             __alignof__(struct scatterlist));
 }
 
-static void esp_ssg_unref(struct xfrm_state *x, void *tmp, struct sk_buff *skb)
+static void esp_ssg_unref(struct xfrm_state *x, void *tmp, struct sk_buff *skb, bool already_unref)
 {
        struct crypto_aead *aead = x->data;
        int extralen = 0;
@@ -130,10 +130,13 @@ static void esp_ssg_unref(struct xfrm_state *x, void *tmp, struct sk_buff *skb)
        /* Unref skb_frag_pages in the src scatterlist if necessary.
         * Skip the first sg which comes from skb->data.
         */
-       if (req->src != req->dst)
-               for (sg = sg_next(req->src); sg; sg = sg_next(sg))
+       if (already_unref || req->src != req->dst) {
+               struct scatterlist *src = already_unref ? esp_req_sg(aead, req) : req->src;
+
+               for (sg = sg_next(src); sg; sg = sg_next(sg))
                        skb_page_unref(page_to_netmem(sg_page(sg)),
                                       skb->pp_recycle);
+       }
 }
 
 #ifdef CONFIG_INET6_ESPINTCP
@@ -254,7 +257,7 @@ static void esp_output_done(void *data, int err)
        }
 
        tmp = ESP_SKB_CB(skb)->tmp;
-       esp_ssg_unref(x, tmp, skb);
+       esp_ssg_unref(x, tmp, skb, false);
        kfree(tmp);
 
        esp_output_encap_csum(skb);
@@ -600,8 +603,10 @@ int esp6_output_tail(struct xfrm_state *x, struct sk_buff *skb, struct esp_info
                err = skb_to_sgvec(skb, dsg,
                                   (unsigned char *)esph - skb->data,
                                   assoclen + ivlen + esp->clen + alen);
-               if (unlikely(err < 0))
+               if (unlikely(err < 0)) {
+                       esp_ssg_unref(x, tmp, skb, true);
                        goto error_free;
+               }
        }
 
        if ((x->props.flags & XFRM_STATE_ESN))
@@ -634,7 +639,7 @@ int esp6_output_tail(struct xfrm_state *x, struct sk_buff *skb, struct esp_info
        }
 
        if (sg != dsg)
-               esp_ssg_unref(x, tmp, skb);
+               esp_ssg_unref(x, tmp, skb, false);
 
        if (!err && x->encap && x->encap->encap_type == TCP_ENCAP_ESPINTCP)
                err = esp_output_tail_tcp(x, skb);