From: Vasily Averin <vvs@virtuozzo.com>
To: Eric Dumazet <eric.dumazet@gmail.com>, Jakub Kicinski <kuba@kernel.org>
Cc: netdev <netdev@vger.kernel.org>,
"David S. Miller" <davem@davemloft.net>,
"David S. Miller" <davem@davemloft.net>,
Hideaki YOSHIFUJI <yoshfuji@linux-ipv6.org>,
David Ahern <dsahern@kernel.org>,
Julian Wiedmann <jwi@linux.ibm.com>,
Christoph Paasch <christoph.paasch@gmail.com>,
linux-kernel@vger.kernel.org, kernel@openvz.org
Subject: [PATCH net v10] skb_expand_head() adjust skb->truesize incorrectly
Date: Fri, 22 Oct 2021 13:28:37 +0300 [thread overview]
Message-ID: <644330dd-477e-0462-83bf-9f514c41edd1@virtuozzo.com> (raw)
In-Reply-To: <2721362c-462b-878f-9e09-9f6c4353c73d@gmail.com>
Christoph Paasch reports [1] about incorrect skb->truesize
after skb_expand_head() call in ip6_xmit.
This may happen because of two reasons:
- skb_set_owner_w() for newly cloned skb is called too early,
before pskb_expand_head() where truesize is adjusted for (!skb-sk) case.
- pskb_expand_head() does not adjust truesize in (skb->sk) case.
In this case sk->sk_wmem_alloc should be adjusted too.
[1] https://lkml.org/lkml/2021/8/20/1082
Fixes: f1260ff15a71 ("skbuff: introduce skb_expand_head()")
Fixes: 2d85a1b31dde ("ipv6: ip6_finish_output2: set sk into newly allocated nskb")
Reported-by: Christoph Paasch <christoph.paasch@gmail.com>
Signed-off-by: Vasily Averin <vvs@virtuozzo.com>
---
v10: is_skb_wmem() was moved into separate header (it depends on net/tcp.h)
use it after pskb_expand_head() insted of strange sock_edemux check
v9: restored sock_edemux check
v8: clone non-wmem skb
v7 (from kuba@):
shift more magic into helpers,
follow Eric's advice and don't inherit non-wmem skbs for now
v6: fixed delta,
improved comments
v5: fixed else condition, thanks to Eric
reworked update of expanded skb,
added corresponding comments
v4: decided to use is_skb_wmem() after pskb_expand_head() call
fixed 'return (EXPRESSION);' in os_skb_wmem according to Eric
Dumazet
v3: removed __pskb_expand_head(),
added is_skb_wmem() helper for skb with wmem-compatible destructors
there are 2 ways to use it:
- before pskb_expand_head(), to create skb clones
- after successfull pskb_expand_head() to change owner on extended
skb.
v2: based on patch version from Eric Dumazet,
added __pskb_expand_head() function, which can be forced
to adjust skb->truesize and sk->sk_wmem_alloc.
net/core/skbuff.c | 36 +++++++++++++++++++++++-------------
net/core/sock_destructor.h | 12 ++++++++++++
2 files changed, 35 insertions(+), 13 deletions(-)
create mode 100644 net/core/sock_destructor.h
diff --git a/net/core/skbuff.c b/net/core/skbuff.c
index 2170bea2c7de..fe9358437380 100644
--- a/net/core/skbuff.c
+++ b/net/core/skbuff.c
@@ -80,6 +80,7 @@
#include <linux/indirect_call_wrapper.h>
#include "datagram.h"
+#include "sock_destructor.h"
struct kmem_cache *skbuff_head_cache __ro_after_init;
static struct kmem_cache *skbuff_fclone_cache __ro_after_init;
@@ -1804,30 +1805,39 @@ EXPORT_SYMBOL(skb_realloc_headroom);
struct sk_buff *skb_expand_head(struct sk_buff *skb, unsigned int headroom)
{
int delta = headroom - skb_headroom(skb);
+ int osize = skb_end_offset(skb);
+ struct sock *sk = skb->sk;
if (WARN_ONCE(delta <= 0,
"%s is expecting an increase in the headroom", __func__))
return skb;
- /* pskb_expand_head() might crash, if skb is shared */
- if (skb_shared(skb)) {
+ delta = SKB_DATA_ALIGN(delta);
+ /* pskb_expand_head() might crash, if skb is shared. */
+ if (skb_shared(skb) || !is_skb_wmem(skb)) {
struct sk_buff *nskb = skb_clone(skb, GFP_ATOMIC);
- if (likely(nskb)) {
- if (skb->sk)
- skb_set_owner_w(nskb, skb->sk);
- consume_skb(skb);
- } else {
- kfree_skb(skb);
- }
+ if (unlikely(!nskb))
+ goto fail;
+
+ if (sk)
+ skb_set_owner_w(nskb, sk);
+ consume_skb(skb);
skb = nskb;
}
- if (skb &&
- pskb_expand_head(skb, SKB_DATA_ALIGN(delta), 0, GFP_ATOMIC)) {
- kfree_skb(skb);
- skb = NULL;
+ if (pskb_expand_head(skb, delta, 0, GFP_ATOMIC))
+ goto fail;
+
+ if (sk && is_skb_wmem(skb)) {
+ delta = skb_end_offset(skb) - osize;
+ refcount_add(delta, &sk->sk_wmem_alloc);
+ skb->truesize += delta;
}
return skb;
+
+fail:
+ kfree_skb(skb);
+ return NULL;
}
EXPORT_SYMBOL(skb_expand_head);
diff --git a/net/core/sock_destructor.h b/net/core/sock_destructor.h
new file mode 100644
index 000000000000..2f396e6bfba5
--- /dev/null
+++ b/net/core/sock_destructor.h
@@ -0,0 +1,12 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+#ifndef _NET_CORE_SOCK_DESTRUCTOR_H
+#define _NET_CORE_SOCK_DESTRUCTOR_H
+#include <net/tcp.h>
+
+static inline bool is_skb_wmem(const struct sk_buff *skb)
+{
+ return skb->destructor == sock_wfree ||
+ skb->destructor == __sock_wfree ||
+ (IS_ENABLED(CONFIG_INET) && skb->destructor == tcp_wfree);
+}
+#endif
--
2.32.0
next prev parent reply other threads:[~2021-10-22 10:29 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <20210920111259.18f9cc01@kicinski-fedora-pc1c0hjn.dhcp.thefacebook.com>
2021-09-20 21:41 ` [PATCH net v8] skb_expand_head() adjust skb->truesize incorrectly Vasily Averin
2021-09-21 5:21 ` Vasily Averin
2021-10-04 13:00 ` [PATCH net v9] " Vasily Averin
2021-10-04 13:14 ` Vasily Averin
2021-10-04 19:26 ` Eric Dumazet
2021-10-05 5:57 ` Vasily Averin
2021-10-20 16:14 ` Eric Dumazet
2021-10-20 16:18 ` Eric Dumazet
2021-10-22 10:28 ` Vasily Averin [this message]
2021-10-22 19:32 ` [PATCH net v10] " Eric Dumazet
2021-10-22 20:50 ` patchwork-bot+netdevbpf
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