[PATCH v2 02/10] zram: avoid invalid memory access in zram_exit()

From: Jiang Liu
Date: Tue Jun 04 2013 - 12:11:22 EST

Memory for zram->disk object may have already been freed after returning
from destroy_device(zram), then it's unsafe for zram_reset_device(zram)
to access zram->disk again.

We can't solve this bug by flipping the order of destroy_device(zram)
and zram_reset_device(zram), that will cause deadlock issues to the
zram sysfs handler.

So fix it by holding an extra reference to zram->disk before calling

Signed-off-by: Jiang Liu <jiang.liu@xxxxxxxxxx>
Cc: stable@xxxxxxxxxxxxxxx
drivers/staging/zram/zram_drv.c | 2 ++
1 file changed, 2 insertions(+)

diff --git a/drivers/staging/zram/zram_drv.c b/drivers/staging/zram/zram_drv.c
index 0a07de4..5a2f20b 100644
--- a/drivers/staging/zram/zram_drv.c
+++ b/drivers/staging/zram/zram_drv.c
@@ -722,8 +722,10 @@ static void __exit zram_exit(void)
for (i = 0; i < num_devices; i++) {
zram = &zram_devices[i];

+ get_disk(zram->disk);
+ put_disk(zram->disk);

unregister_blkdev(zram_major, "zram");

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