Subject: Re: [PATCH v2 1/6] Add ancillary bus support

From: Leon Romanovsky <[email-masked]>
Date: Thu, 8 Oct 2020 20:20:11 +0300

On Mon, Oct 05, 2020 at 11:24:41AM -0700, Dave Ertman wrote:
> Add support for the Ancillary Bus, ancillary_device and ancillary_driver.
> It enables drivers to create an ancillary_device and bind an
> ancillary_driver to it.
>
> The bus supports probe/remove shutdown and suspend/resume callbacks.
> Each ancillary_device has a unique string based id; driver binds to
> an ancillary_device based on this id through the bus.
>
> Co-developed-by: Kiran Patil <[email-masked]>
> Signed-off-by: Kiran Patil <[email-masked]>
> Co-developed-by: Ranjani Sridharan <[email-masked]>
> Signed-off-by: Ranjani Sridharan <[email-masked]>
> Co-developed-by: Fred Oh <[email-masked]>
> Signed-off-by: Fred Oh <[email-masked]>
> Reviewed-by: Pierre-Louis Bossart <[email-masked]>
> Reviewed-by: Shiraz Saleem <[email-masked]>
> Reviewed-by: Parav Pandit <[email-masked]>
> Reviewed-by: Dan Williams <[email-masked]>
> Signed-off-by: Dave Ertman <[email-masked]>
> ---

<...>

> +
> +static const struct ancillary_device_id *ancillary_match_id(const struct ancillary_device_id *id,
> +							    const struct ancillary_device *ancildev)
> +{
> +	while (id->name[0]) {
> +		const char *p = strrchr(dev_name(&ancildev->dev), '.');
> +		int match_size;
> +
> +		if (!p) {
> +			id++;
> +			continue;
> +		}
> +		match_size = p - dev_name(&ancildev->dev);
> +
> +		/* use dev_name(&ancildev->dev) prefix before last '.' char to match to */
> +		if (!strncmp(dev_name(&ancildev->dev), id->name, match_size))

This check is wrong, it causes to wrong matching if strlen(id->name) > match_size
In my case, the trigger was:
[    5.175848] ancillary:ancillary_match_id: dev mlx5_core.ib.0, id mlx5_core.ib_rep

>From cf8f10af72f9e0d57c7ec077d59238cc12b0650f Mon Sep 17 00:00:00 2001
From: Leon Romanovsky <[email-masked]>
Date: Thu, 8 Oct 2020 19:40:03 +0300
Subject: [PATCH] fixup! Fixes to ancillary bus

Signed-off-by: Leon Romanovsky <[email-masked]>
---
 drivers/bus/ancillary.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/drivers/bus/ancillary.c b/drivers/bus/ancillary.c
index 54858f744ef5..615ce40ef8e4 100644
--- a/drivers/bus/ancillary.c
+++ b/drivers/bus/ancillary.c
@@ -31,8 +31,10 @@ static const struct ancillary_device_id *ancillary_match_id(const struct ancilla
 		match_size = p - dev_name(&ancildev->dev);

 		/* use dev_name(&ancildev->dev) prefix before last '.' char to match to */
-		if (!strncmp(dev_name(&ancildev->dev), id->name, match_size))
+		if (match_size == strlen(id->name) && !strncmp(dev_name(&ancildev->dev), id->name, match_size)) {
 			return id;
+		}
+
 		id++;
 	}
 	return NULL;
--
2.26.2

> +			return id;
> +		id++;
> +	}
> +	return NULL;
> +}