[PATCH net] RDS-TCP: Recover correctly from pskb_pull()/pksb_trim() failure in rds_tcp_data_recv

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 <redacted>
---
 net/rds/tcp_recv.c |   11 +++++++++--
 1 files changed, 9 insertions(+), 2 deletions(-)

diff --git a/net/rds/tcp_recv.c b/net/rds/tcp_recv.c
index fbc5ef8..27a9921 100644
--- a/net/rds/tcp_recv.c
+++ b/net/rds/tcp_recv.c

@@ -214,8 +214,15 @@ 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 -> "

-- 
1.7.1

On 10/26/2015 9:46 AM, Sowmini Varadhan wrote:

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 <redacted>
---

Good one. Probably we should get this fix in stable versions as
well. It seems to be applicable for all v2.6.32+ stable versions.

FWIW,
Acked-by: Santosh Shilimkar <redacted>

Regards,
Santosh

From: Sowmini Varadhan <redacted>
Date: Mon, 26 Oct 2015 12:46:37 -0400

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 <redacted>

Applied and queued up for -stable, thanks.