linux-kernel - [PATCH 3.2 49/52] RDS-TCP: Recover correctly from pskb_pull()/pksb_trim() failure in rds_tcp_data

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Message-ID: <lsq.1448404439.373023057@decadent.org.uk>
Date:	Tue, 24 Nov 2015 22:33:59 +0000
From:	Ben Hutchings <ben@...adent.org.uk>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:	akpm@...ux-foundation.org,
	"Santosh Shilimkar" <santosh.shilimkar@...cle.com>,
	"Sowmini Varadhan" <sowmini.varadhan@...cle.com>,
	"David S. Miller" <davem@...emloft.net>
Subject: [PATCH 3.2 49/52] RDS-TCP: Recover correctly from pskb_pull()/pksb_trim()
  failure in rds_tcp_data_recv

3.2.74-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Sowmini Varadhan <sowmini.varadhan@...cle.com>

[ Upstream commit 8ce675ff39b9958d1c10f86cf58e357efaafc856 ]

Either of pskb_pull() or pskb_trim() may fail under low memory conditions.
If rds_tcp_data_recv() ignores such failures, the application will
receive corrupted data because the skb has not been correctly
carved to the RDS datagram size.

Avoid this by handling pskb_pull/pskb_trim failure in the same
manner as the skb_clone failure: bail out of rds_tcp_data_recv(), and
retry via the deferred call to rds_send_worker() that gets set up on
ENOMEM from rds_tcp_read_sock()

Signed-off-by: Sowmini Varadhan <sowmini.varadhan@...cle.com>
Acked-by: Santosh Shilimkar <santosh.shilimkar@...cle.com>
Signed-off-by: David S. Miller <davem@...emloft.net>
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 net/rds/tcp_recv.c | 11 +++++++++--
 1 file changed, 9 insertions(+), 2 deletions(-)

--- a/net/rds/tcp_recv.c
+++ b/net/rds/tcp_recv.c
@@ -235,8 +235,15 @@ static int rds_tcp_data_recv(read_descri
 			}
 
 			to_copy = min(tc->t_tinc_data_rem, left);
-			pskb_pull(clone, offset);
-			pskb_trim(clone, to_copy);
+			if (!pskb_pull(clone, offset) ||
+			    pskb_trim(clone, to_copy)) {
+				pr_warn("rds_tcp_data_recv: pull/trim failed "
+					"left %zu data_rem %zu skb_len %d\n",
+					left, tc->t_tinc_data_rem, skb->len);
+				kfree_skb(clone);
+				desc->error = -ENOMEM;
+				goto out;
+			}
 			skb_queue_tail(&tinc->ti_skb_list, clone);
 
 			rdsdebug("skb %p data %p len %d off %u to_copy %zu -> "

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