net: Unmap fragment page once iterator is done

Callers of skb_seq_read() are currently forced to call skb_abort_seq_read()
even when consuming all the data because the last call to skb_seq_read (the
one that returns 0 to indicate the end) fails to unmap the last fragment page.

With this patch callers will be allowed to traverse the SKB data by calling
skb_prepare_seq_read() once and repeatedly calling skb_seq_read() as originally
intended (and documented in the original commit 677e90eda), that is, only call
skb_abort_seq_read() if the sequential read is actually aborted.

Signed-off-by: Wedson Almeida Filho <wedsonaf@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

3 files changed, 6 insertions, 3 deletions

diff --git a/drivers/scsi/libiscsi_tcp.c b/drivers/scsi/libiscsi_tcp.c
index 552e8a2b6f5f..448eae850b9c 100644
--- a/drivers/scsi/libiscsi_tcp.c
+++ b/drivers/scsi/libiscsi_tcp.c
@@ -906,7 +906,6 @@ int iscsi_tcp_recv_skb(struct iscsi_conn *conn, struct sk_buff *skb,
                         ISCSI_DBG_TCP(conn, "no more data avail. Consumed %d\n",
                                       consumed);
                         *status = ISCSI_TCP_SKB_DONE;
-                        skb_abort_seq_read(&seq);
                         goto skb_done;
                 }
                 BUG_ON(segment->copied >= segment->size);
diff --git a/net/batman-adv/main.c b/net/batman-adv/main.c
index 51aafd669cbb..08125f3f6064 100644
--- a/net/batman-adv/main.c
+++ b/net/batman-adv/main.c
@@ -473,7 +473,6 @@ __be32 batadv_skb_crc32(struct sk_buff *skb, u8 *payload_ptr)
                 crc = crc32c(crc, data, len);
                 consumed += len;
         }
-        skb_abort_seq_read(&st);
 
         return htonl(crc);
 }
diff --git a/net/core/skbuff.c b/net/core/skbuff.c
index edf37578e21e..9f73eca29fbe 100644
--- a/net/core/skbuff.c
+++ b/net/core/skbuff.c
@@ -2541,8 +2541,13 @@ unsigned int skb_seq_read(unsigned int consumed, const u8 **data,
         unsigned int block_limit, abs_offset = consumed + st->lower_offset;
         skb_frag_t *frag;
 
-        if (unlikely(abs_offset >= st->upper_offset))
+        if (unlikely(abs_offset >= st->upper_offset)) {
+                if (st->frag_data) {
+                        kunmap_atomic(st->frag_data);
+                        st->frag_data = NULL;
+                }
                 return 0;
+        }
 
 next_skb:
         block_limit = skb_headlen(st->cur_skb) + st->stepped_offset;