linux-kernel - Re: [PATCH] stm class: fix device leak in open error path

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Date:   Fri, 18 Nov 2016 13:55:58 +0200
From:   Alexander Shishkin <alexander.shishkin@...ux.intel.com>
To:     Johan Hovold <johan@...nel.org>
Cc:     linux-kernel@...r.kernel.org, Johan Hovold <johan@...nel.org>
Subject: Re: [PATCH] stm class: fix device leak in open error path

Johan Hovold <johan@...nel.org> writes:

> Make sure to drop the reference taken by class_find_device() also on
> allocation errors in open().
>
> Fixes: 7bd1d4093c2f ("stm class: Introduce an abstraction for...")
> Signed-off-by: Johan Hovold <johan@...nel.org>

Good catch, thanks! I'm going to change it a bit to look like this
if you don't mind:

diff --git a/drivers/hwtracing/stm/core.c b/drivers/hwtracing/stm/core.c
index 51f81d64ca..cf6c9ea14c 100644
--- a/drivers/hwtracing/stm/core.c
+++ b/drivers/hwtracing/stm/core.c
@@ -361,7 +361,7 @@ static int stm_char_open(struct inode *inode, struct file *file)
        struct stm_file *stmf;
        struct device *dev;
        unsigned int major = imajor(inode);
-       int err = -ENODEV;
+       int err = -ENOMEM;

        dev = class_find_device(&stm_class, NULL, &major, major_match);
        if (!dev)
@@ -369,8 +369,9 @@ static int stm_char_open(struct inode *inode, struct file *file)

        stmf = kzalloc(sizeof(*stmf), GFP_KERNEL);
        if (!stmf)
-               return -ENOMEM;
+               goto err_put_device;

+       err = -ENODEV;
        stm_output_init(&stmf->output);
        stmf->stm = to_stm_device(dev);

@@ -382,9 +383,10 @@ static int stm_char_open(struct inode *inode, struct file *file)
        return nonseekable_open(inode, file);

 err_free:
+       kfree(stmf);
+err_put_device:
        /* matches class_find_device() above */
        put_device(dev);
-       kfree(stmf);

        return err;
 }

Regards,
--
Alex