[3.13.y-ckt stable] Patch "RDS-TCP: Recover correctly from pskb_pull()/pksb_trim() failure in rds_tcp_data_recv" has been added to staging queue

[Kamal Mostafa]

This is a note to let you know that I have just added a patch titled

    RDS-TCP: Recover correctly from pskb_pull()/pksb_trim() failure in rds_tcp_data_recv

to the linux-3.13.y-queue branch of the 3.13.y-ckt extended stable tree 
which can be found at:

    http://kernel.ubuntu.com/git/ubuntu/linux.git/log/?h=linux-3.13.y-queue

This patch is scheduled to be released in version 3.13.11-ckt31.

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 3.13.y-ckt tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Kamal

------

>From 7d3f68bd6165224d80dba44cc956269252bd7bbd Mon Sep 17 00:00:00 2001
From: Sowmini Varadhan <sowmini.varadhan at oracle.com>
Date: Mon, 26 Oct 2015 12:46:37 -0400
Subject: RDS-TCP: Recover correctly from pskb_pull()/pksb_trim() failure in
 rds_tcp_data_recv

[ 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 at oracle.com>
Acked-by: Santosh Shilimkar <santosh.shilimkar at oracle.com>
Signed-off-by: David S. Miller <davem at davemloft.net>
Signed-off-by: Kamal Mostafa <kamal at canonical.com>
---
 net/rds/tcp_recv.c | 11 +++++++++--
 1 file changed, 9 insertions(+), 2 deletions(-)

diff --git a/net/rds/tcp_recv.c b/net/rds/tcp_recv.c
index 4fac4f2..8b33d99 100644
--- a/net/rds/tcp_recv.c
+++ b/net/rds/tcp_recv.c
@@ -234,8 +234,15 @@ static int rds_tcp_data_recv(read_descriptor_t *desc, struct sk_buff *skb,
 			}

 			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 -> "
--
1.9.1