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

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.

[akpm@linux-foundation.org: fix coding stype, per Sergey]
Signed-off-by: Jerome Marchand <jmarchan@redhat.com>
Acked-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Cc: Minchan Kim <minchan@kernel.org>
Cc: <stable@vger.kernel.org>	[4.2+]
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 4 insertions, 3 deletions

diff --git a/drivers/block/zram/zram_drv.c b/drivers/block/zram/zram_drv.c
index 47915d736f8d..370c2f76016d 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);
@@ -1367,10 +1366,12 @@ 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);
         return ret ? ret : count;