linux-kernel - Re: [PATCH 01/14] misc: fastrpc: Fix use-after-free and race in fastrpc_map

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Message-ID: <YxIST6Nb2iYIr+XO@linaro.org>
Date:   Fri, 2 Sep 2022 17:25:19 +0300
From:   Abel Vesa <abel.vesa@...aro.org>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:     Andy Gross <agross@...nel.org>,
        Bjorn Andersson <bjorande@....qualcomm.com>,
        Konrad Dybcio <konrad.dybcio@...ainline.org>,
        Srinivas Kandagatla <srinivas.kandagatla@...aro.org>,
        Amol Maheshwari <amahesh@....qualcomm.com>,
        Rob Herring <robh@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>,
        Ekansh Gupta <ekangupt@....qualcomm.com>,
        Arnd Bergmann <arnd@...db.de>, linux-arm-msm@...r.kernel.org,
        devicetree@...r.kernel.org,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Ola Jeppsson <ola@...p.com>
Subject: Re: [PATCH 01/14] misc: fastrpc: Fix use-after-free and race in
 fastrpc_map_find

On 22-09-02 15:25:10, Greg Kroah-Hartman wrote:
> On Fri, Sep 02, 2022 at 04:13:31PM +0300, Abel Vesa wrote:
> > Currently, there is a race window between the point when the mutex is
> > unlocked in fastrpc_map_lookup and the reference count increasing
> > (fastrpc_map_get) in fastrpc_map_find, which can also lead to
> > use-after-free.
> > 
> > So lets merge fastrpc_map_find into fastrpc_map_lookup which allows us
> > to both protect the maps list by also taking the &fl->lock spinlock and
> > the reference count, since the spinlock will be released only after.
> > Add take_ref argument to make this suitable for all callers.
> > 
> > Co-developed-by: Ola Jeppsson <ola@...p.com>
> > Signed-off-by: Ola Jeppsson <ola@...p.com>
> > Signed-off-by: Abel Vesa <abel.vesa@...aro.org>
> > ---
> >  drivers/misc/fastrpc.c | 41 +++++++++++++++++++++--------------------
> >  1 file changed, 21 insertions(+), 20 deletions(-)
> 
> What commit does this fix?  Should it go to stable trees?

Will specify in the next version.

> 
> Try splitting this series up into 2, one for 6.0-final with bugfixes to
> resolve issues found, and the next one on top of that for new features.

Fair point. Will do in the next version.

> 
> thanks,
> 
> greg k-h