From: Zhu Yanjun <zyjzyj2000@gmail.com>
To: Daniel Borkmann <daniel@iogearbox.net>
Cc: "Zhu Yanjun" <yanjun.zhu@intel.com>,
"Björn Töpel" <bjorn.topel@intel.com>,
"Karlsson, Magnus" <magnus.karlsson@intel.com>,
netdev <netdev@vger.kernel.org>,
jonathan.lemon@gmail.com
Subject: Re: [PATCH v2 1/1] xdp: avoid calling kfree twice
Date: Wed, 9 Dec 2020 12:30:55 +0800 [thread overview]
Message-ID: <CAD=hENc8CmxdPeWbQ=4GFdtQCoCqUc87xS5sq+VePZEGC2-Z6g@mail.gmail.com> (raw)
In-Reply-To: <f68c2d75-4a51-445d-cecf-894b65cb8d55@iogearbox.net>
On Wed, Dec 9, 2020 at 1:12 AM Daniel Borkmann <daniel@iogearbox.net> wrote:
>
> On 12/9/20 6:03 AM, Zhu Yanjun wrote:
> > In the function xdp_umem_pin_pages, if npgs != umem->npgs and
> > npgs >= 0, the function xdp_umem_unpin_pages is called. In this
> > function, kfree is called to handle umem->pgs, and then in the
> > function xdp_umem_pin_pages, kfree is called again to handle
> > umem->pgs. Eventually, umem->pgs is freed twice.
> >
> > Acked-by: Björn Töpel <bjorn.topel@intel.com>
> > Signed-off-by: Zhu Yanjun <yanjun.zhu@intel.com>
>
> Please also fix up the commit log according to Bjorn's prior feedback [0].
> If it's just a cleanup, it should state so, the commit message right now
> makes it sound like an actual double free bug.
The umem->pgs is actually freed twice. Since umem->pgs is set to NULL
after the first kfree,
the second kfree would not trigger call trace.
IMO, the commit log is very clear about this.
Zhu Yanjun
>
> [0] https://lore.kernel.org/netdev/0fef898d-cf5e-ef1b-6c35-c98669e9e0ed@intel.com/
next prev parent reply other threads:[~2020-12-09 4:31 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-12-09 5:03 [PATCH v2 1/1] xdp: avoid calling kfree twice Zhu Yanjun
2020-12-08 17:12 ` Daniel Borkmann
2020-12-09 4:30 ` Zhu Yanjun [this message]
2020-12-09 10:44 ` Toke Høiland-Jørgensen
2020-12-10 4:34 ` Zhu Yanjun
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