Re: [PATCH v2] ipmi: Fix kernel panic at ipmi_ssif_thread()

[joechang]

Hi Corey,

I really appreciate your patience and detail code review.
I re-generate new patch and send new patch to you.
Please feel free to feedback to me if something need to modify from the 
new patch..

Thank you,
Joseph.

Corey Minyard æ 2017-03-27 20:32 åå:
> On 03/27/2017 02:31 AM, Joeseph Chang wrote:
> > From: Joeseph Chang <joechang@xxxxxxxxxxxxxx>
> >
> > Since patch v1 touch ssif_info->multi_pos and ssif_info->multi_data
> > after ssif_i2c_send(). msg_written_handler can be called at any time
> > after ssif_i2c_send(). There is possible to have concurrent access to
> > ssif_info->multi_pos or ssif_info->multi_data at msg_written_handler.
> >
> > Revert patch v1 and add new local pointer "i2c_data" which point to
> > i2c data and size that will be sent out to avoid concurrent access in
> > msg_written_handler().
> >
> > Signed-off-by: Joeseph Chang <joechang@xxxxxxxxxxxxxx>
> > ---
> >   drivers/char/ipmi/ipmi_ssif.c | 24 ++++++++++++------------
> >   1 file changed, 12 insertions(+), 12 deletions(-)
> >
> > diff --git a/drivers/char/ipmi/ipmi_ssif.c 
> > b/drivers/char/ipmi/ipmi_ssif.c
> > index 39346ee..f36f018 100644
> > --- a/drivers/char/ipmi/ipmi_ssif.c
> > +++ b/drivers/char/ipmi/ipmi_ssif.c
> > @@ -852,6 +852,7 @@ static void msg_written_handler(struct ssif_info 
> > *ssif_info, int result,
> >   				unsigned char *data, unsigned int len)
> >   {
> >   	int rv;
> > +	unsigned char *i2c_data;
>
> The variable should be in the block where it is used.  The basic rule
> is to limit scope as much as possible.
>
> The name is also a little vague, though not terrible.
>
> >     	/* We are single-threaded here, so no need for a lock. */
> >   	if (result < 0) {
> > @@ -899,13 +900,22 @@ static void msg_written_handler(struct ssif_info 
> > *ssif_info, int result,
> >   			left = 32;
> >   		/* Length byte. */
> >   		ssif_info->multi_data[ssif_info->multi_pos] = left;
> > +		i2c_data = ssif_info->multi_data + ssif_info->multi_pos;
> > +		ssif_info->multi_pos += left;
> > +		if (left < 32)
> > +			/*
> > +			 * Write is finished.  Note that we must end
> > +			 * with a write of less than 32 bytes to
> > +			 * complete the transaction, even if it is
> > +			 * zero bytes.
> > +			 */
> > +			ssif_info->multi_data = NULL;
>
> Can you make this change not relative to the previous change?  Just do
> a "git rebase -i ...." and squash the
> changes.
>
> I saw your previous emails, but I can't take those because of the
> comments at the top and the text from
> the reply.  You can add comments to a submission that don't go into
> git, just put them after the '---" in
> the header.
>
> Thanks,
>
> -corey
>
> >     		rv = ssif_i2c_send(ssif_info, msg_written_handler,
> >   				  I2C_SMBUS_WRITE,
> >   				  SSIF_IPMI_MULTI_PART_REQUEST_MIDDLE,
> > -				  ssif_info->multi_data + ssif_info->multi_pos,
> > +				  i2c_data,
> >   				  I2C_SMBUS_BLOCK_DATA);
> > -
> >   		if (rv < 0) {
> >   			/* request failed, just return the error. */
> >   			ssif_inc_stat(ssif_info, send_errors);
> > @@ -914,16 +924,6 @@ static void msg_written_handler(struct ssif_info 
> > *ssif_info, int result,
> >   				pr_info("Error from i2c_non_blocking_op(3)\n");
> >   			msg_done_handler(ssif_info, -EIO, NULL, 0);
> >   		}
> > -
> > -		ssif_info->multi_pos += left;
> > -		if (left < 32)
> > -			/*
> > -			 * Write is finished.  Note that we must end
> > -			 * with a write of less than 32 bytes to
> > -			 * complete the transaction, even if it is
> > -			 * zero bytes.
> > -			 */
> > -			ssif_info->multi_data = NULL;
> >   	} else {
> >   		/* Ready to request the result. */
> >   		unsigned long oflags, *flags;