linux-kernel - Re: [PATCHv2] firmware: Correct handling of fw_state_wait

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Message-ID: <CAB=NE6Xj0TpwMVTDWtEaYAqSn8HdVapXqUf7j4a+i2f+zdkSZA@mail.gmail.com>
Date:   Tue, 17 Jan 2017 10:21:44 -0600
From:   "Luis R. Rodriguez" <mcgrof@...nel.org>
To:     Jakub Kicinski <jakub.kicinski@...ronome.com>,
        Chris Wilson <chris@...is-wilson.co.uk>,
        linux-kernel-dev@...khoff.com
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Bjorn Andersson <bjorn.andersson@...aro.org>,
        Daniel Wagner <daniel.wagner@...-carit.de>,
        "Luis R . Rodriguez" <mcgrof@...nel.org>,
        Ming Lei <ming.lei@...onical.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        oss-drivers@...ronome.com
Subject: Re: [PATCHv2] firmware: Correct handling of fw_state_wait_timeout()
 return value

On Tue, Jan 17, 2017 at 10:15 AM, Luis R. Rodriguez <mcgrof@...nel.org> wrote:
> On Tue, Jan 17, 2017 at 03:35:05PM +0000, Jakub Kicinski wrote:
>> Commit 5d47ec02c37e ("firmware: Correct handling of fw_state_wait()
>> return value") made the assumption that any error returned from
>> fw_state_wait_timeout() means FW load has to be aborted.  This is
>> incorrect, FW load only has to be aborted when load timed out or
>> has been interrupted.  Otherwise, if wait exited because of a wake
>> up, the waking thread (in firmware_loading_store()) had already
>> performed the clean up - deleted fw_buf from the pending list and
>> set fw_priv->buf to NULL.
>>
>> Example NULL dereference which occurs because requsted firmware
>> could not be found by UMH:
>>
>> nfp 0000:02:00.0: Direct firmware load for AMDA0081-0001.cat failed with error -2
>> nfp 0000:02:00.0: Falling back to user helper
>> BUG: unable to handle kernel NULL pointer dereference at 0000000000000038
>> IP: _request_firmware+0x7fd/0x910
>> PGD 0
>>
>> Oops: 0000 [#1] PREEMPT SMP
>> CPU: 4 PID: 1981 Comm: insmod Tainted: G           O    4.10.0-rc3-perf-00404-g575a284323c2 #78
>> Hardware name: Dell Inc. PowerEdge T630/0W9WXC, BIOS 1.2.10 03/10/2015
>> task: ffff919b81a99a80 task.stack: ffffb3bac5668000
>> RIP: 0010:_request_firmware+0x7fd/0x910
>> RSP: 0018:ffffb3bac566b978 EFLAGS: 00010246
>> RAX: 00000000fffffffe RBX: ffff919b9b2becc0 RCX: ffff919b9b2bece8
>> RDX: ffff919b81a99a80 RSI: 0000000000000206 RDI: 0000000000000000
>> RBP: ffffb3bac566b9e0 R08: ffff919b9f30f4b8 R09: 0000000000000002
>> R10: 00000120d2b47b48 R11: 0000000000000000 R12: ffffb3bac566ba18
>> R13: ffff919b823f4780 R14: ffff919b907c5000 R15: 0000000000003a98
>> FS:  00007fae4d803740(0000) GS:ffff919b9f300000(0000) knlGS:0000000000000000
>> CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
>> CR2: 0000000000000038 CR3: 00000008507b8000 CR4: 00000000001406e0
>> Call Trace:
>> request_firmware+0x37/0x50
>> ...
>>
>> Fixes: 5d47ec02c37e ("firmware: Correct handling of fw_state_wait() return value")
>> Signed-off-by: Jakub Kicinski <jakub.kicinski@...ronome.com>
>> ---
>> v2:
>>  - improve commit message.
>> ---
>>  drivers/base/firmware_class.c | 2 +-
>>  1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/drivers/base/firmware_class.c b/drivers/base/firmware_class.c
>> index 4497d263209f..ce142e6b2c72 100644
>> --- a/drivers/base/firmware_class.c
>> +++ b/drivers/base/firmware_class.c
>> @@ -1020,7 +1020,7 @@ static int _request_firmware_load(struct firmware_priv *fw_priv,
>>       }
>>
>>       retval = fw_state_wait_timeout(&buf->fw_st, timeout);
>> -     if (retval < 0) {
>> +     if (retval == -ETIMEDOUT || retval == -ERESTARTSYS) {
>>               mutex_lock(&fw_lock);
>>               fw_load_abort(fw_priv);
>>               mutex_unlock(&fw_lock);
>
> This is a bit messy, two other similar issues were reported before
> and upon review I suggested Patrick Bruenn's fix with a better commit
> log seems best fit. Patrick sent a patch Jan 4, 2017 but never followed up
> despite my feedback on a small change on the commit log message [0]. Can you
> try that and if that fixes it can you adjust the commit log accordingly? Please
> note the preferred solution would be:
>
> diff --git a/drivers/base/firmware_class.c b/drivers/base/firmware_class.c
> index b9ac348e8d33..c530f8b4af01 100644
> --- a/drivers/base/firmware_class.c
> +++ b/drivers/base/firmware_class.c
> @@ -542,6 +542,8 @@ static struct firmware_priv *to_firmware_priv(struct device *dev)
>
>  static void __fw_load_abort(struct firmware_buf *buf)
>  {
> +       if (!buf)
> +               return;
>         /*
>          * There is a small window in which user can write to 'loading'
>          * between loading done and disappearance of 'loading'
>
> [0] https://http://lkml.kernel.org/r/20170104174227.GO13946@wotan.suse.de

Actually Patrick did follow up with a new patch today but I just saw
it was not as I recommended above. Patrick can you send a new one with
your good commit log with the above change ? Can you both confirm it
fixes the issue?

 Luis