linux-kernel - Re: [PATCH v3 03/15] scsi: ufs: verify command tag validity

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Message-ID: <CAC5umyjwgKvyZpMsk7J1n5M+G+bjTh+rEUNGZcDgnSD2DZG1NQ@mail.gmail.com>
Date:	Wed, 21 Oct 2015 23:48:31 +0900
From:	Akinobu Mita <akinobu.mita@...il.com>
To:	Yaniv Gardi <ygardi@...eaurora.org>
Cc:	Rob Herring <robherring2@...il.com>,
	Jej B <James.Bottomley@...senpartnership.com>,
	Paul Bolle <pebolle@...cali.nl>,
	Christoph Hellwig <hch@...radead.org>,
	LKML <linux-kernel@...r.kernel.org>,
	"linux-scsi@...r.kernel.org" <linux-scsi@...r.kernel.org>,
	linux-arm-msm@...r.kernel.org, Santosh Y <santoshsy@...il.com>,
	linux-scsi-owner@...r.kernel.org,
	Subhash Jadavani <subhashj@...eaurora.org>,
	Gilad Broner <gbroner@...eaurora.org>,
	Dolev Raviv <draviv@...eaurora.org>,
	Vinayak Holikatti <vinholikatti@...il.com>,
	"James E.J. Bottomley" <JBottomley@...n.com>
Subject: Re: [PATCH v3 03/15] scsi: ufs: verify command tag validity

2015-09-02 19:13 GMT+09:00 Yaniv Gardi <ygardi@...eaurora.org>:
> A race condition appear to exist between request completion when
> scsi_done() is called to end the request and set the tag back to
> -1 (at blk_queue_end_tag() scsi_end_request), and scsi layer error
> handling which aborts the command and reuses it to request sense
> data. Sending the request sense is done with tag which was set to -1
> and so it is invalid.
> Assert command tag passed from scsi layer is valid.
>
> Signed-off-by: Gilad Broner <gbroner@...eaurora.org>
> Signed-off-by: Yaniv Gardi <ygardi@...eaurora.org>
>
> ---
>  drivers/scsi/ufs/ufshcd.c | 24 ++++++++++++++++++++++--
>  1 file changed, 22 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/scsi/ufs/ufshcd.c b/drivers/scsi/ufs/ufshcd.c
> index 2d3ebca..8860a57 100644
> --- a/drivers/scsi/ufs/ufshcd.c
> +++ b/drivers/scsi/ufs/ufshcd.c
> @@ -190,6 +190,10 @@ static int ufshcd_config_pwr_mode(struct ufs_hba *hba,
>                 struct ufs_pa_layer_attr *desired_pwr_mode);
>  static int ufshcd_change_power_mode(struct ufs_hba *hba,
>                              struct ufs_pa_layer_attr *pwr_mode);
> +static inline bool ufshcd_valid_tag(struct ufs_hba *hba, int tag)
> +{
> +       return tag >= 0 && tag < hba->nutrs;
> +}
>
>  static inline int ufshcd_enable_irq(struct ufs_hba *hba)
>  {
> @@ -1310,6 +1314,12 @@ static int ufshcd_queuecommand(struct Scsi_Host *host, struct scsi_cmnd *cmd)
>         hba = shost_priv(host);
>
>         tag = cmd->request->tag;
> +       if (!ufshcd_valid_tag(hba, tag)) {
> +               dev_err(hba->dev,
> +                       "%s: invalid command tag %d: cmd=0x%p, cmd->request=0x%p",
> +                       __func__, tag, cmd, cmd->request);
> +               BUG();
> +       }

Is it better to avoid BUG() by WARN_ON() and return if possible?
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