linux-kernel - Possible memory leak in cafe

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Message-ID: <9aac6eca-e553-0b49-d5ce-e49029b52fdc@ispras.ru>
Date:   Tue, 22 Aug 2017 19:26:23 +0300
From:   Anton Volkov <avolkov@...ras.ru>
To:     corbet@....net
Cc:     mchehab@...nel.org, linux-media@...r.kernel.org,
        linux-kernel@...r.kernel.org, ldv-project@...uxtesting.org,
        Alexey Khoroshilov <khoroshilov@...ras.ru>
Subject: Possible memory leak in cafe_ccic.ko

Hello.

While searching for races in the Linux kernel I've come across 
"drivers/media/platform/marvell-ccic/cafe_ccic.ko" module. Here are 
questions that I came up with while analyzing results. Lines are given 
using the info from Linux v4.12.

Consider the following case:

Thread 1:                  Thread 2:
                            mcam_v4l_release
                            ->mcam_free_dma_bufs
                                cam->dma_bufs[i] = NULL
                                cam->nbufs = 0
cafe_pci_resume                (mcam-core.c: line 413)
->mccic_resume
   ->mcam_read_setup
     ->mcam_alloc_dma_bufs
       cam->dma_bufs[i] =
          dma_alloc_coherent()
          (mcam-core.c: line 381)

It looks like mcam_v4l_release() doesn't really shut the device down. In 
this case cafe_pci_resume() leaks memory for cam->dma_bufs[i] after 
mcam_v4l_release() freed and poisoned them. Is this feasible from your 
point of view?

Thank you for your time.

-- Anton Volkov
Linux Verification Center, ISPRAS
web: http://linuxtesting.org
e-mail: avolkov@...ras.ru