[PATCH 4.2.y-ckt 142/268] zram: don't call idr_remove() from zram_remove()

From: Kamal Mostafa
Date: Wed Jan 27 2016 - 16:27:09 EST


4.2.8-ckt3 -stable review patch. If anyone has any objections, please let me know.

---8<------------------------------------------------------------

From: Jerome Marchand <jmarchan@xxxxxxxxxx>

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.

[akpm@xxxxxxxxxxxxxxxxxxxx: fix coding stype, per Sergey]
Signed-off-by: Jerome Marchand <jmarchan@xxxxxxxxxx>
Acked-by: Sergey Senozhatsky <sergey.senozhatsky@xxxxxxxxx>
Cc: Minchan Kim <minchan@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Kamal Mostafa <kamal@xxxxxxxxxxxxx>
---
drivers/block/zram/zram_drv.c | 7 ++++---
1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/drivers/block/zram/zram_drv.c b/drivers/block/zram/zram_drv.c
index 763301c..6a706f5 100644
--- a/drivers/block/zram/zram_drv.c
+++ b/drivers/block/zram/zram_drv.c
@@ -1319,7 +1319,6 @@ 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);
@@ -1361,10 +1360,12 @@ 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;
--
1.9.1