[PATCH 3.12 46/83] gso: handle new frag_list of frags GRO packets

Greg Kroah-Hartman
2013-12-06T21:52:57Z

From: Herbert Xu <herbert@gondor.apana.org.au>

[ Upstream commit 9d8506cc2d7ea1f911c72c100193a3677f6668c3 ]

Recently GRO started generating packets with frag_lists of frags.
This was not handled by GSO, thus leading to a crash.

Thankfully these packets are of a regular form and are easy to
handle. This patch handles them in two ways. For completely
non-linear frag_list entries, we simply continue to iterate over
the frag_list frags once we exhaust the normal frags. For frag_list
entries with linear parts, we call pskb_trim on the first part
of the frag_list skb, and then process the rest of the frags in
the usual way.

This patch also kills a chunk of dead frag_list code that has
obviously never ever been run since it ends up generating a bogus
GSO-segmented packet with a frag_list entry.

Future work is planned to split super big packets into TSO
ones.

Fixes: 8a29111c7ca6 ("net: gro: allow to build full sized skb")
Reported-by: Christoph Paasch <christoph.paasch@uclouvain.be>
Reported-by: Jerry Chu <hkchu@google.com>
Reported-by: Sander Eikelenboom <linux@eikelenboom.it>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: Eric Dumazet <edumazet@google.com>
Tested-by: Sander Eikelenboom <linux@eikelenboom.it>
Tested-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
net/core/skbuff.c | 75 ++++++++++++++++++++++++++++++++++++------------------
1 file changed, 50 insertions(+), 25 deletions(-)

--- a/net/core/skbuff.c
+++ b/net/core/skbuff.c
@@ -2755,6 +2755,7 @@ struct sk_buff *skb_segment(struct sk_bu
struct sk_buff *segs = NULL;
struct sk_buff *tail = NULL;
struct sk_buff *fskb = skb_shinfo(skb)->frag_list;
+ skb_frag_t *skb_frag = skb_shinfo(skb)->frags;
unsigned int mss = skb_shinfo(skb)->gso_size;
unsigned int doffset = skb->data - skb_mac_header(skb);
unsigned int offset = doffset;
@@ -2794,16 +2795,38 @@ struct sk_buff *skb_segment(struct sk_bu
if (hsize > len || !sg)
hsize = len;

- if (!hsize && i >= nfrags) {
- BUG_ON(fskb->len != len);
+ if (!hsize && i >= nfrags && skb_headlen(fskb) &&
+ (skb_headlen(fskb) == len || sg)) {
+ BUG_ON(skb_headlen(fskb) > len);
+
+ i = 0;
+ nfrags = skb_shinfo(fskb)->nr_frags;
+ skb_frag = skb_shinfo(fskb)->frags;
+ pos += skb_headlen(fskb);
+
+ while (pos < offset + len) {
+ BUG_ON(i >= nfrags);
+
+ size = skb_frag_size(skb_frag);
+ if (pos + size > offset + len)
+ break;
+
+ i++;
+ pos += size;
+ skb_frag++;
+ }

- pos += len;
nskb = skb_clone(fskb, GFP_ATOMIC);
fskb = fskb->next;

if (unlikely(!nskb))
goto err;

+ if (unlikely(pskb_trim(nskb, len))) {
+ kfree_skb(nskb);
+ goto err;
+ }
+
hsize = skb_end_offset(nskb);
if (skb_cow_head(nskb, doffset + headroom)) {
kfree_skb(nskb);
@@ -2847,7 +2870,7 @@ struct sk_buff *skb_segment(struct sk_bu
nskb->data - tnl_hlen,
doffset + tnl_hlen);

- if (fskb != skb_shinfo(skb)->frag_list)
+ if (nskb->len == len + doffset)
goto perform_csum_check;

if (!sg) {
@@ -2865,8 +2888,28 @@ struct sk_buff *skb_segment(struct sk_bu

skb_shinfo(nskb)->tx_flags = skb_shinfo(skb)->tx_flags & SKBTX_SHARED_FRAG;

- while (pos < offset + len && i < nfrags) {
- *frag = skb_shinfo(skb)->frags[i];
+ while (pos < offset + len) {
+ if (i >= nfrags) {
+ BUG_ON(skb_headlen(fskb));
+
+ i = 0;
+ nfrags = skb_shinfo(fskb)->nr_frags;
+ skb_frag = skb_shinfo(fskb)->frags;
+
+ BUG_ON(!nfrags);
+
+ fskb = fskb->next;
+ }
+
+ if (unlikely(skb_shinfo(nskb)->nr_frags >=
+ MAX_SKB_FRAGS)) {
+ net_warn_ratelimited(
+ "skb_segment: too many frags: %u %u\n",
+ pos, mss);
+ goto err;
+ }
+
+ *frag = *skb_frag;
__skb_frag_ref(frag);
size = skb_frag_size(frag);

@@ -2879,6 +2922,7 @@ struct sk_buff *skb_segment(struct sk_bu

if (pos + size <= offset + len) {
i++;
+ skb_frag++;
pos += size;
} else {
skb_frag_size_sub(frag, pos + size - (offset + len));
@@ -2888,25 +2932,6 @@ struct sk_buff *skb_segment(struct sk_bu
frag++;
}

- if (pos < offset + len) {
- struct sk_buff *fskb2 = fskb;
-
- BUG_ON(pos + fskb->len != offset + len);
-
- pos += fskb->len;
- fskb = fskb->next;
-
- if (fskb2->next) {
- fskb2 = skb_clone(fskb2, GFP_ATOMIC);
- if (!fskb2)
- goto err;
- } else
- skb_get(fskb2);
-
- SKB_FRAG_ASSERT(nskb);
- skb_shinfo(nskb)->frag_list = fskb2;
- }
-
skip_fraglist:
nskb->data_len = len - hsize;
nskb->len += nskb->data_len;