From: Vasily Averin <vvs@virtuozzo.com>
To: Christoph Paasch <christoph.paasch@gmail.com>,
Jakub Kicinski <kuba@kernel.org>,
Eric Dumazet <eric.dumazet@gmail.com>
Cc: "David S. Miller" <davem@davemloft.net>,
Hideaki YOSHIFUJI <yoshfuji@linux-ipv6.org>,
David Ahern <dsahern@kernel.org>, netdev <netdev@vger.kernel.org>,
linux-kernel@vger.kernel.org, kernel@openvz.org,
Julian Wiedmann <jwi@linux.ibm.com>
Subject: [PATCH net v8] skb_expand_head() adjust skb->truesize incorrectly
Date: Tue, 21 Sep 2021 00:41:34 +0300 [thread overview]
Message-ID: <be927ca4-6fd7-ce89-e472-bb1e5a0dc2a9@virtuozzo.com> (raw)
In-Reply-To: <20210920111259.18f9cc01@kicinski-fedora-pc1c0hjn.dhcp.thefacebook.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>
---
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.
---
include/net/sock.h | 1 +
net/core/skbuff.c | 33 +++++++++++++++++++++------------
net/core/sock.c | 8 ++++++++
3 files changed, 30 insertions(+), 12 deletions(-)
diff --git a/include/net/sock.h b/include/net/sock.h
index 95b2577..173d58c 100644
--- a/include/net/sock.h
+++ b/include/net/sock.h
@@ -1695,6 +1695,7 @@ struct sk_buff *sock_wmalloc(struct sock *sk, unsigned long size, int force,
gfp_t priority);
void __sock_wfree(struct sk_buff *skb);
void sock_wfree(struct sk_buff *skb);
+bool is_skb_wmem(const struct sk_buff *skb);
struct sk_buff *sock_omalloc(struct sock *sk, unsigned long size,
gfp_t priority);
void skb_orphan_partial(struct sk_buff *skb);
diff --git a/net/core/skbuff.c b/net/core/skbuff.c
index f931176..4b49f63 100644
--- a/net/core/skbuff.c
+++ b/net/core/skbuff.c
@@ -1804,30 +1804,39 @@ struct sk_buff *skb_realloc_headroom(struct sk_buff *skb, unsigned int 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;
+ delta = SKB_DATA_ALIGN(delta);
/* pskb_expand_head() might crash, if skb is shared */
- if (skb_shared(skb)) {
+ 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) {
+ 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.c b/net/core/sock.c
index 950f1e7..6cbda43 100644
--- a/net/core/sock.c
+++ b/net/core/sock.c
@@ -2227,6 +2227,14 @@ void skb_set_owner_w(struct sk_buff *skb, struct sock *sk)
}
EXPORT_SYMBOL(skb_set_owner_w);
+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);
+}
+EXPORT_SYMBOL(is_skb_wmem);
+
static bool can_skb_orphan_partial(const struct sk_buff *skb)
{
#ifdef CONFIG_TLS_DEVICE
--
1.8.3.1
next parent reply other threads:[~2021-09-20 21:43 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 ` Vasily Averin [this message]
2021-09-21 5:21 ` [PATCH net v8] skb_expand_head() adjust skb->truesize incorrectly 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 ` [PATCH net v10] " Vasily Averin
2021-10-22 19:32 ` Eric Dumazet
2021-10-22 20:50 ` patchwork-bot+netdevbpf
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