Patch "zram: don't call idr_remove() from zram_remove()" has been added to the 4.3-stable tree

This is a note to let you know that I've just added the patch titled

zram: don't call idr_remove() from zram_remove()

to the 4.3-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
zram-don-t-call-idr_remove-from-zram_remove.patch
and it can be found in the queue-4.3 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Jerome Marchand <[email protected]>
Date: Fri, 15 Jan 2016 16:54:48 -0800
Subject: zram: don't call idr_remove() from zram_remove()

From: Jerome Marchand <[email protected]>

commit 17ec4cd985780a7e30aa45bb8f272237c12502a4 upstream.

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.

---
 drivers/block/zram/zram_drv.c |    7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

@@ -1324,7 +1324,6 @@ 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);

@@ -1366,10 +1365,12 @@ static ssize_t hot_remove_store(struct c
 	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);
 	return ret ? ret : count;

Patches currently in stable-queue which might be from [email protected] are

queue-4.3/zram-don-t-call-idr_remove-from-zram_remove.patch