sock: fix sg page frag coalescing in sk_alloc_sg

[ Upstream commit 144fe2bfd236dc814eae587aea7e2af03dbdd755 ]

Current sg coalescing logic in sk_alloc_sg() (latter is used by tls and
sockmap) is not quite correct in that we do fetch the previous sg entry,
however the subsequent check whether the refilled page frag from the
socket is still the same as from the last entry with prior offset and
length matching the start of the current buffer is comparing always the
first sg list entry instead of the prior one.

Fixes: 3c4d7559159b ("tls: kernel TLS support")
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Dave Watson <davejwatson@fb.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/net/core/sock.c b/net/core/sock.c
index 3b6d02854e57736254975963c45369515f369ddc..f82843756534cb55d649d40e18098f4ba7671f8a 100644 (file)
--- a/net/core/sock.c
+++ b/net/core/sock.c
@@ -2270,9 +2270,9 @@ int sk_alloc_sg(struct sock *sk, int len, struct scatterlist *sg,
                pfrag->offset += use;
 
                sge = sg + sg_curr - 1;
-               if (sg_curr > first_coalesce && sg_page(sg) == pfrag->page &&
-                   sg->offset + sg->length == orig_offset) {
-                       sg->length += use;
+               if (sg_curr > first_coalesce && sg_page(sge) == pfrag->page &&
+                   sge->offset + sge->length == orig_offset) {
+                       sge->length += use;
                } else {
                        sge = sg + sg_curr;
                        sg_unmark_end(sge);