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bh=W4m3XgQBNeuN2I+tcLBHvg4pj9JGolU+Q45d0wqY2ik=; b=S9yN0eZIvjntn6Zxjcp5SbLAPv+gT8CnDRIL2YKIxUFkSreRNi3nSIRMwdowQabLjCmwaJ 2UfH/ogOWj9d4MPWgb2waRqcw0+e0gNszvK4Q8Ofn6gqkYNoYvcnYzWJTkg+9X2+2W8e0I Rtqj97sSZAcHQACjb8ldKufv/Ncan60= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-58-fBh9G0ABNlqkzzVy8Bq2cw-1; Fri, 14 May 2021 15:26:26 -0400 X-MC-Unique: fBh9G0ABNlqkzzVy8Bq2cw-1 Received: from smtp.corp.redhat.com (int-mx01.intmail.prod.int.phx2.redhat.com [10.5.11.11]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 545AFEC1A0; Fri, 14 May 2021 19:26:25 +0000 (UTC) Received: from [10.10.117.64] (ovpn-117-64.rdu2.redhat.com [10.10.117.64]) by smtp.corp.redhat.com (Postfix) with ESMTP id 33D6D136F5; Fri, 14 May 2021 19:26:24 +0000 (UTC) Subject: Re: [PATCH] fdc: check drive block device before usage (CVE-2021-20196) To: Thomas Huth , P J P , Max Reitz , Kevin Wolf , Qemu-block References: <20210123100345.642933-1-ppandit@redhat.com> <6881ef3c-99a1-1f5f-cca5-0850ec2bd6cf@redhat.com> From: John Snow Message-ID: <89fb8d54-707a-9965-75e2-665d4cb07d63@redhat.com> Date: Fri, 14 May 2021 15:26:23 -0400 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.8.1 MIME-Version: 1.0 In-Reply-To: <6881ef3c-99a1-1f5f-cca5-0850ec2bd6cf@redhat.com> X-Scanned-By: MIMEDefang 2.79 on 10.5.11.11 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=jsnow@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 8bit Received-SPF: pass client-ip=170.10.133.124; envelope-from=jsnow@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -34 X-Spam_score: -3.5 X-Spam_bar: --- X-Spam_report: (-3.5 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.699, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, NICE_REPLY_A=-0.001, RCVD_IN_DNSWL_LOW=-0.7, RCVD_IN_MSPIKE_H4=0.001, RCVD_IN_MSPIKE_WL=0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=unavailable autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: qemu-stable@nongnu.org, Gaoning Pan , QEMU Developers , Prasad J Pandit Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On 5/14/21 3:23 PM, Thomas Huth wrote: > On 23/01/2021 11.03, P J P wrote: >> From: Prasad J Pandit >> >> While processing ioport command in 'fdctrl_write_dor', device >> controller may select a drive which is not initialised with a >> block device. This may result in a NULL pointer dereference. >> Add checks to avoid it. >> >> Fixes: CVE-2021-20196 >> Reported-by: Gaoning Pan >> Buglink: https://bugs.launchpad.net/qemu/+bug/1912780 >> Signed-off-by: Prasad J Pandit >> --- >>   hw/block/fdc.c | 11 +++++++++-- >>   1 file changed, 9 insertions(+), 2 deletions(-) >> >> diff --git a/hw/block/fdc.c b/hw/block/fdc.c >> index 3636874432..13a9470d19 100644 >> --- a/hw/block/fdc.c >> +++ b/hw/block/fdc.c >> @@ -1429,7 +1429,9 @@ static void fdctrl_write_dor(FDCtrl *fdctrl, >> uint32_t value) >>           } >>       } >>       /* Selected drive */ >> -    fdctrl->cur_drv = value & FD_DOR_SELMASK; >> +    if (fdctrl->drives[value & FD_DOR_SELMASK].blk) { >> +        fdctrl->cur_drv = value & FD_DOR_SELMASK; >> +    } >>       fdctrl->dor = value; >>   } >> @@ -1894,6 +1896,10 @@ static uint32_t fdctrl_read_data(FDCtrl *fdctrl) >>       uint32_t pos; >>       cur_drv = get_cur_drv(fdctrl); >> +    if (!cur_drv->blk) { >> +        FLOPPY_DPRINTF("No drive connected\n"); >> +        return 0; >> +    } >>       fdctrl->dsr &= ~FD_DSR_PWRDOWN; >>       if (!(fdctrl->msr & FD_MSR_RQM) || !(fdctrl->msr & FD_MSR_DIO)) { >>           FLOPPY_DPRINTF("error: controller not ready for reading\n"); >> @@ -2420,7 +2426,8 @@ static void fdctrl_write_data(FDCtrl *fdctrl, >> uint32_t value) >>           if (pos == FD_SECTOR_LEN - 1 || >>               fdctrl->data_pos == fdctrl->data_len) { >>               cur_drv = get_cur_drv(fdctrl); >> -            if (blk_pwrite(cur_drv->blk, fd_offset(cur_drv), >> fdctrl->fifo, >> +            if (cur_drv->blk == NULL >> +                || blk_pwrite(cur_drv->blk, fd_offset(cur_drv), >> fdctrl->fifo, >>                              BDRV_SECTOR_SIZE, 0) < 0) { >>                   FLOPPY_DPRINTF("error writing sector %d\n", >>                                  fd_sector(cur_drv)); >> > > Ping again! > > Could anybody review / pick this up? > >  Thomas > Yep. Not forgotten, despite appearances. Clearing my Python review backlog, then onto FDC/IDE. In the meantime, anything anyone else happens to feel comfortable staging won't upset me any. I don't insist they go through my tree right now.