[PATCH 2/2] net: mana: Check if netdev/napi_alloc_frag returns single page

[Tim Gardner]

From: Haiyang Zhang <haiyangz at microsoft.com>

BugLink: https://bugs.launchpad.net/bugs/2018593

netdev/napi_alloc_frag() may fall back to single page which is smaller
than the requested size.
Add error checking to avoid memory overwritten.

Signed-off-by: Haiyang Zhang <haiyangz at microsoft.com>
Signed-off-by: Jakub Kicinski <kuba at kernel.org>
(cherry picked from commit df18f2da302f169e1a29098c6ca3b474f1b0269e)
Signed-off-by: Tim Gardner <tim.gardner at canonical.com>
---
 drivers/net/ethernet/microsoft/mana/mana_en.c | 15 +++++++++++++++
 1 file changed, 15 insertions(+)

diff --git a/drivers/net/ethernet/microsoft/mana/mana_en.c b/drivers/net/ethernet/microsoft/mana/mana_en.c
index 2ab3caefac25..202f2f34f016 100644
--- a/drivers/net/ethernet/microsoft/mana/mana_en.c
+++ b/drivers/net/ethernet/microsoft/mana/mana_en.c
@@ -553,6 +553,14 @@ static int mana_pre_alloc_rxbufs(struct mana_port_context *mpc, int new_mtu)
 			va = netdev_alloc_frag(mpc->rxbpre_alloc_size);
 			if (!va)
 				goto error;
+
+			page = virt_to_head_page(va);
+			/* Check if the frag falls back to single page */
+			if (compound_order(page) <
+			    get_order(mpc->rxbpre_alloc_size)) {
+				put_page(page);
+				goto error;
+			}
 		} else {
 			page = dev_alloc_page();
 			if (!page)
@@ -1504,6 +1512,13 @@ static void *mana_get_rxfrag(struct mana_rxq *rxq, struct device *dev,
 
 		if (!va)
 			return NULL;
+
+		page = virt_to_head_page(va);
+		/* Check if the frag falls back to single page */
+		if (compound_order(page) < get_order(rxq->alloc_size)) {
+			put_page(page);
+			return NULL;
+		}
 	} else {
 		page = dev_alloc_page();
 		if (!page)
-- 
2.34.1