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([2804:14c:125:811b:fbbc:3360:40c4:fb64]) by smtp.gmail.com with ESMTPSA id t1sm3059094qto.78.2021.05.04.12.07.28 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 04 May 2021 12:07:30 -0700 (PDT) Subject: Re: [PATCH] media: em28xx: Fix possible memory leak of em28xx struct To: Shuah Khan , mchehab@kernel.org Cc: linux-media@vger.kernel.org, linux-kernel@vger.kernel.org, hverkuil-cisco@xs4all.nl References: <20210503173716.21652-1-igormtorrente@gmail.com> From: Igor Torrente Message-ID: Date: Tue, 4 May 2021 16:07:27 -0300 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.10.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 5/3/21 5:06 PM, Shuah Khan wrote: > Hi Igor, > > On 5/3/21 11:37 AM, Igor Matheus Andrade Torrente wrote: >> The em28xx struct kref isn't being decreased after an error in the >> em28xx_ir_init, leading to a possible memory leak. >> >> A kref_put is added to the error handler code. >> >> Signed-off-by: Igor Matheus Andrade Torrente >> --- >>   drivers/media/usb/em28xx/em28xx-input.c | 7 +++++-- >>   1 file changed, 5 insertions(+), 2 deletions(-) >> >> diff --git a/drivers/media/usb/em28xx/em28xx-input.c >> b/drivers/media/usb/em28xx/em28xx-input.c >> index 5aa15a7a49de..b89527014cad 100644 >> --- a/drivers/media/usb/em28xx/em28xx-input.c >> +++ b/drivers/media/usb/em28xx/em28xx-input.c >> @@ -720,7 +720,8 @@ static int em28xx_ir_init(struct em28xx *dev) >>               dev->board.has_ir_i2c = 0; >>               dev_warn(&dev->intf->dev, >>                    "No i2c IR remote control device found.\n"); >> -            return -ENODEV; >> +            err = -ENODEV; >> +            goto ref_put; > > This doesn't look right. em28xx_init_buttons() is already happened and > em28xx_shutdown_buttons() needs to be done from fini. fini needs to run > with this ref. If ref is released here, device might be released before > em28xx_shutdown_buttons() can run leading to potential use-after-free > Thanks for the feedback. I sent a patch V2 that I think fix the problem pointed out. >>           } >>       } >> @@ -735,7 +736,7 @@ static int em28xx_ir_init(struct em28xx *dev) >>       ir = kzalloc(sizeof(*ir), GFP_KERNEL); >>       if (!ir) >> -        return -ENOMEM; >> +        goto ref_put; > > This doesn't look right. Same comment as above. fini accounts for null > ir. > >       em28xx_shutdown_buttons(dev); > >        /* skip detach on non attached boards */ >        if (!ir) >                goto ref_put; > > >>       rc = rc_allocate_device(RC_DRIVER_SCANCODE); >>       if (!rc) >>           goto error; >> @@ -839,6 +840,8 @@ static int em28xx_ir_init(struct em28xx *dev) >>       dev->ir = NULL; >>       rc_free_device(rc); >>       kfree(ir); >> +ref_put: >> +    kref_put(&dev->ref, em28xx_free_device); >>       return err; >>   } >> > > thanks, > -- Shuah Best regard, --- Igor M. A. Torrente