linux-kernel - [PATCH v2] tun: avoid high-order page allocation for packet header

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [thread-next>] [day] [month] [year] [list]

Message-ID: <20230731230736.109216-1-trdgn@amazon.com>
Date:   Mon, 31 Jul 2023 16:07:36 -0700
From:   Tahsin Erdogan <trdgn@...zon.com>
To:     "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>,
        Herbert Xu <herbert@...dor.apana.org.au>
CC:     Tahsin Erdogan <trdgn@...zon.com>, <netdev@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>
Subject: [PATCH v2] tun: avoid high-order page allocation for packet header

When GSO is not enabled and a packet is transmitted via writev(), all
payload is treated as header which requires a contiguous memory allocation.
This allocation request is harder to satisfy, and may even fail if there is
enough fragmentation.

Note that sendmsg() code path limits the linear copy length, so this change
makes writev() and sendmsg() more consistent.

Signed-off-by: Tahsin Erdogan <trdgn@...zon.com>
---
v2: replace linear == 0 with !linear
v1: https://lore.kernel.org/all/20230726030936.1587269-1-trdgn@amazon.com/
 drivers/net/tun.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/drivers/net/tun.c b/drivers/net/tun.c
index d75456adc62a..4c57804f4cbd 100644
--- a/drivers/net/tun.c
+++ b/drivers/net/tun.c
@@ -1523,7 +1523,7 @@ static struct sk_buff *tun_alloc_skb(struct tun_file *tfile,
 	int err;
 
 	/* Under a page?  Don't bother with paged skb. */
-	if (prepad + len < PAGE_SIZE || !linear)
+	if (prepad + len < PAGE_SIZE)
 		linear = len;
 
 	skb = sock_alloc_send_pskb(sk, prepad + linear, len - linear, noblock,
@@ -1838,6 +1838,9 @@ static ssize_t tun_get_user(struct tun_struct *tun, struct tun_file *tfile,
 			 */
 			zerocopy = false;
 		} else {
+			if (!linear)
+				linear = min_t(size_t, good_linear, copylen);
+
 			skb = tun_alloc_skb(tfile, align, copylen, linear,
 					    noblock);
 		}
-- 
2.41.0