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

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[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 <[hidden email]>
---
 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

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

Sergey Senozhatsky-3
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 <[hidden email]>

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 <[hidden email]>
+ Cc: <[hidden email]>

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

Sergey Senozhatsky-3
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 <[hidden email]>
> + Cc: <[hidden email]>
>
> 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
> >
>
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Re: [PATCH] zram: don't call idr_remove() from zram_remove()

Minchan Kim-2
In reply to this post by Jerome Marchand
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 <[hidden email]>

Acked-by: Minchan Kim <[hidden email]> with Sergey's nitpick

Thanks!