[PATCH] zram: don't call idr_remove() from zram_remove()

[PATCH] zram: don't call idr_remove() from zram_remove()

[Jerome Marchand]

The use of idr_remove() is forbidden in the callback functions of
idr_for_each(). It is therefore unsafe to call idr_remove in
zram_remove().
This patch moves the call to idr_remove() from zram_remove() to
hot_remove_store(). In the detroy_devices() path, idrs are removed by
idr_destroy().
This solves an use-after-free detected by KASan.

Signed-off-by: Jerome Marchand <jmarchan@redhat.com>
---
 drivers/block/zram/zram_drv.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/drivers/block/zram/zram_drv.c b/drivers/block/zram/zram_drv.c
index 47915d7..5e86e1d 100644
--- a/drivers/block/zram/zram_drv.c
+++ b/drivers/block/zram/zram_drv.c
@@ -1325,7 +1325,6 @@ static int zram_remove(struct zram *zram)
 
 	pr_info("Removed device: %s\n", zram->disk->disk_name);
 
-	idr_remove(&zram_index_idr, zram->disk->first_minor);
 	blk_cleanup_queue(zram->disk->queue);
 	del_gendisk(zram->disk);
 	put_disk(zram->disk);
@@ -1367,9 +1366,10 @@ static ssize_t hot_remove_store(struct class *class,
 	mutex_lock(&zram_index_mutex);
 
 	zram = idr_find(&zram_index_idr, dev_id);
-	if (zram)
+	if (zram) {
 		ret = zram_remove(zram);
-	else
+		idr_remove(&zram_index_idr, dev_id);
+	} else
 		ret = -ENODEV;
 
 	mutex_unlock(&zram_index_mutex);
-- 
2.5.0

Re: [PATCH] zram: don't call idr_remove() from zram_remove()

[Sergey Senozhatsky]

Cc Andrew

On (01/14/16 14:03), Jerome Marchand wrote:
> The use of idr_remove() is forbidden in the callback functions of
> idr_for_each(). It is therefore unsafe to call idr_remove in
> zram_remove().
> This patch moves the call to idr_remove() from zram_remove() to
> hot_remove_store(). In the detroy_devices() path, idrs are removed by
> idr_destroy().
> This solves an use-after-free detected by KASan.

thanks, good catch! wow, I must be blind or stupid, or both.


Acked-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>

a nano nitpick to add curly braces in the else clause.
but, what is more important, may I please ask you to add -stable [4.2+]

> Signed-off-by: Jerome Marchand <jmarchan@redhat.com>
+ Cc: <stable@vger.kernel.org>

and to resend the patch?



idr added in 4.2
https://git.kernel.org/cgit/linux/kernel/git/stable/linux-stable.git/tree/drivers/block/zram/zram_drv.c?id=refs/tags/v4.2

	-ss

> ---
>  drivers/block/zram/zram_drv.c | 6 +++---
>  1 file changed, 3 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/block/zram/zram_drv.c b/drivers/block/zram/zram_drv.c
> index 47915d7..5e86e1d 100644
> --- a/drivers/block/zram/zram_drv.c
> +++ b/drivers/block/zram/zram_drv.c
> @@ -1325,7 +1325,6 @@ static int zram_remove(struct zram *zram)
>  
>  	pr_info("Removed device: %s\n", zram->disk->disk_name);
>  
> -	idr_remove(&zram_index_idr, zram->disk->first_minor);
>  	blk_cleanup_queue(zram->disk->queue);
>  	del_gendisk(zram->disk);
>  	put_disk(zram->disk);
> @@ -1367,9 +1366,10 @@ static ssize_t hot_remove_store(struct class *class,
>  	mutex_lock(&zram_index_mutex);
>  
>  	zram = idr_find(&zram_index_idr, dev_id);
> -	if (zram)
> +	if (zram) {
>  		ret = zram_remove(zram);
> -	else
> +		idr_remove(&zram_index_idr, dev_id);

+	} else {
>  		ret = -ENODEV;
+	}


>  	mutex_unlock(&zram_index_mutex);
> -- 
> 2.5.0
> 

Re: [PATCH] zram: don't call idr_remove() from zram_remove()

[Sergey Senozhatsky]

On (01/15/16 09:43), Sergey Senozhatsky wrote:
[..]
> a nano nitpick to add curly braces in the else clause.
> but, what is more important, may I please ask you to add -stable [4.2+]
> 
> > Signed-off-by: Jerome Marchand <jmarchan@redhat.com>
> + Cc: <stable@vger.kernel.org>
> 
> and to resend the patch?
> 

Jerome, please disregard my requests. Andrew has handled it. Thanks to both of you!

	-ss

> idr added in 4.2
> https://git.kernel.org/cgit/linux/kernel/git/stable/linux-stable.git/tree/drivers/block/zram/zram_drv.c?id=refs/tags/v4.2
> 
> 	-ss
> 
> > ---
> >  drivers/block/zram/zram_drv.c | 6 +++---
> >  1 file changed, 3 insertions(+), 3 deletions(-)
> > 
> > diff --git a/drivers/block/zram/zram_drv.c b/drivers/block/zram/zram_drv.c
> > index 47915d7..5e86e1d 100644
> > --- a/drivers/block/zram/zram_drv.c
> > +++ b/drivers/block/zram/zram_drv.c
> > @@ -1325,7 +1325,6 @@ static int zram_remove(struct zram *zram)
> >  
> >  	pr_info("Removed device: %s\n", zram->disk->disk_name);
> >  
> > -	idr_remove(&zram_index_idr, zram->disk->first_minor);
> >  	blk_cleanup_queue(zram->disk->queue);
> >  	del_gendisk(zram->disk);
> >  	put_disk(zram->disk);
> > @@ -1367,9 +1366,10 @@ static ssize_t hot_remove_store(struct class *class,
> >  	mutex_lock(&zram_index_mutex);
> >  
> >  	zram = idr_find(&zram_index_idr, dev_id);
> > -	if (zram)
> > +	if (zram) {
> >  		ret = zram_remove(zram);
> > -	else
> > +		idr_remove(&zram_index_idr, dev_id);
> 
> +	} else {
> >  		ret = -ENODEV;
> +	}
> 
> 
> >  	mutex_unlock(&zram_index_mutex);
> > -- 
> > 2.5.0
> > 
> 

Re: [PATCH] zram: don't call idr_remove() from zram_remove()

[Minchan Kim]

On Thu, Jan 14, 2016 at 02:03:47PM +0100, Jerome Marchand wrote:
> The use of idr_remove() is forbidden in the callback functions of
> idr_for_each(). It is therefore unsafe to call idr_remove in
> zram_remove().
> This patch moves the call to idr_remove() from zram_remove() to
> hot_remove_store(). In the detroy_devices() path, idrs are removed by
> idr_destroy().
> This solves an use-after-free detected by KASan.
> 
> Signed-off-by: Jerome Marchand <jmarchan@redhat.com>

Acked-by: Minchan Kim <minchan@kernel.org> with Sergey's nitpick

Thanks!