From: David Miller <davem@davemloft.net>
To: dhowells@redhat.com
Cc: netdev@vger.kernel.org, linux-afs@lists.infradead.org,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH net 0/7] rxrpc: Fix use of skb_cow_data()
Date: Fri, 30 Aug 2019 14:55:16 -0700 (PDT) [thread overview]
Message-ID: <20190830.145516.687207471361740034.davem@davemloft.net> (raw)
In-Reply-To: <156708405310.26102.7954021163316252673.stgit@warthog.procyon.org.uk>
From: David Howells <dhowells@redhat.com>
Date: Thu, 29 Aug 2019 14:07:33 +0100
> Here's a series of patches that replaces the use of skb_cow_data() in rxrpc
> with skb_unshare() early on in the input process. The problem that is
> being seen is that skb_cow_data() indirectly requires that the maximum
> usage count on an sk_buff be 1, and it may generate an assertion failure in
> pskb_expand_head() if not.
>
> This can occur because rxrpc_input_data() may be still holding a ref when
> it has just attached the sk_buff to the rx ring and given that attachment
> its own ref. If recvmsg happens fast enough, skb_cow_data() can see the
> ref still held by the softirq handler.
>
> Further, a packet may contain multiple subpackets, each of which gets its
> own attachment to the ring and its own ref - also making skb_cow_data() go
> bang.
>
> Fix this by:
...
> There are also patches to improve the rxrpc_skb tracepoint to make sure
> that Tx-derived buffers are identified separately from Rx-derived buffers
> in the trace.
This looks great, thanks for reimplementing this using skb_unshare().
> The patches are tagged here:
>
> git://git.kernel.org/pub/scm/linux/kernel/git/dhowells/linux-fs.git
> rxrpc-fixes-20190827
Pulled, thanks again.
next prev parent reply other threads:[~2019-08-30 21:55 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <20190901065603.432-1-hdanton@sina.com>
2019-08-29 13:07 ` [PATCH net 0/7] rxrpc: Fix use of skb_cow_data() David Howells
2019-08-29 13:07 ` [PATCH net 1/7] rxrpc: Improve jumbo packet counting David Howells
2019-08-29 13:07 ` [PATCH net 2/7] rxrpc: Use info in skbuff instead of reparsing a jumbo packet David Howells
2019-08-29 13:07 ` [PATCH net 3/7] rxrpc: Pass the input handler's data skb reference to the Rx ring David Howells
2019-08-29 13:08 ` [PATCH net 4/7] rxrpc: Abstract out rxtx ring cleanup David Howells
2019-08-29 13:08 ` [PATCH net 5/7] rxrpc: Add a private skb flag to indicate transmission-phase skbs David Howells
2019-08-29 13:08 ` [PATCH net 6/7] rxrpc: Use the tx-phase skb flag to simplify tracing David Howells
2019-08-29 13:08 ` [PATCH net 7/7] rxrpc: Use skb_unshare() rather than skb_cow_data() David Howells
2019-08-30 21:55 ` David Miller [this message]
2019-09-01 7:11 ` David Howells
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