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From: Jiayuan Chen <jiayuan.chen@linux.dev>
To: Jakub Kicinski <kuba@kernel.org>, Hyunwoo Kim <imv4bel@gmail.com>
Cc: dhowells@redhat.com, marc.dionne@auristor.com,
	davem@davemloft.net, edumazet@google.com, pabeni@redhat.com,
	horms@kernel.org, qingfang.deng@linux.dev,
	jiayuan.chen@linux.dev, linux-afs@lists.infradead.org,
	netdev@vger.kernel.org, stable@vger.kernel.org
Subject: Re: [PATCH net v3] rxrpc: Also unshare DATA/RESPONSE packets when paged frags are present
Date: Mon, 11 May 2026 09:54:44 +0800	[thread overview]
Message-ID: <f7f242c1-5f54-4cf7-ac61-ff6e9c70394f@linux.dev> (raw)
In-Reply-To: <20260510084520.476745b5@kernel.org>


On 5/10/26 11:45 PM, Jakub Kicinski wrote:
> On Fri, 8 May 2026 17:53:09 +0900 Hyunwoo Kim wrote:
>>   			    sp->hdr.securityIndex != 0 &&
>> -			    skb_cloned(skb)) {
>> +			    (skb_cloned(skb) ||
>> +			     skb_has_frag_list(skb) ||
>> +			     skb_has_shared_frag(skb))) {
> We seem to be getting a lot of fixes for this issue, and this one is
> incorrect :| Writing to _any_ frags is incorrect. You have to copy
> if skb is not linear. skb_ensure_writable()


There is a issue Simon pointed [1] that triggered 
BUG_ON(skb_shared(skb)) which was fixed by commit d0d5c0cd1e71
skb_cow_data -> __pskb_pull_tail -> pskb_expand_head -> 
BUG_ON(skb_shared(skb))

I think skb_ensure_writable will also trigger such code:
skb_ensure_writable -> pskb_may_pull -> __pskb_pull_tail -> 
pskb_expand_head -> BUG_ON(skb_shared(skb))

LPE will become panic.

[1]: 
https://lore.kernel.org/netdev/20260501155806.222592-3-horms@kernel.org/



      parent reply	other threads:[~2026-05-11  1:54 UTC|newest]

Thread overview: 11+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2026-05-08  8:53 [PATCH net v3] rxrpc: Also unshare DATA/RESPONSE packets when paged frags are present Hyunwoo Kim
2026-05-08 15:45 ` David Howells
2026-05-09  2:32 ` Jiayuan Chen
2026-05-09 14:30 ` Jeffrey E Altman
2026-05-10 15:45 ` Jakub Kicinski
2026-05-10 16:48   ` Hyunwoo Kim
2026-05-10 17:03     ` Jakub Kicinski
2026-05-10 17:05       ` Fernando Fernandez Mancera
2026-05-10 17:05       ` Hyunwoo Kim
2026-05-10 17:23         ` Jakub Kicinski
2026-05-11  1:54   ` Jiayuan Chen [this message]

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