From: David Laight <david.laight.linux@gmail.com>
To: Jamal Hadi Salim <jhs@mojatatu.com>
Cc: netdev@vger.kernel.org, davem@davemloft.net, edumazet@google.com,
kuba@kernel.org, pabeni@redhat.com, horms@kernel.org,
jiri@resnulli.us, victor@mojatatu.com, yimingqian591@gmail.com,
keenanat2000@gmail.com, 2045gemini@gmail.com,
rollkingzzc@gmail.com, toke@redhat.com, dcaratti@redhat.com,
security@kernel.org, linux-kernel@vger.kernel.org,
stable@kernel.org, Rajat Gupta <rajat.gupta@oss.qualcomm.com>
Subject: Re: [PATCH net v5 1/1] net/sched: fix pedit partial COW leading to page cache corruption
Date: Sun, 31 May 2026 19:52:18 +0100 [thread overview]
Message-ID: <20260531195218.5fe29990@pumpkin> (raw)
In-Reply-To: <20260531194241.7d5d7e6e@pumpkin>
On Sun, 31 May 2026 19:42:41 +0100
David Laight <david.laight.linux@gmail.com> wrote:
> On Sun, 31 May 2026 13:25:36 -0400
> Jamal Hadi Salim <jhs@mojatatu.com> wrote:
....
> > >
> > > > + goto bad;
> > > > + if (skb_ensure_writable(skb, min_t(int, skb->len,
> > > > + write_len)))
>
> You've completely missed that the above has to include the write_offset.
And I've missed that write_len isn't the length you are going to write :-(
This version is unreadable....
A few one line comments can make all the difference.
I put these two in for a reason.
It took some effort to find out exactly what they did.
> > /* Ensure any needed headroom is writeable */
> > if (hoffset < 0 && skb_cow(skb, -hoffset)
> > goto bad;
> > /* Ensure the skb is writeable to the end of the area to be written.
> > * The data is pulled into the skb header. */
-- David
prev parent reply other threads:[~2026-05-31 18:52 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-05-31 12:32 [PATCH net v5 1/1] net/sched: fix pedit partial COW leading to page cache corruption Jamal Hadi Salim
2026-05-31 16:15 ` David Laight
2026-05-31 17:25 ` Jamal Hadi Salim
2026-05-31 17:28 ` Jamal Hadi Salim
2026-05-31 18:42 ` David Laight
2026-05-31 18:52 ` David Laight [this message]
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