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zram: avoid invalid memory access in zram_exit() 

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
destroy_device(zram).

Signed-off-by: Jiang Liu <jiang.liu@huawei.com>
Cc: stable@vger.kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Jiang Liu 2013-06-07 00:07:22 +08:00 committed by Greg Kroah-Hartman
parent 0ea0dcff90
commit 6030ea9b35
1 changed files with 2 additions and 0 deletions
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2
drivers/staging/zram/zram_drv.c
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@ -727,8 +727,10 @@ static void __exit zram_exit(void)
for (i = 0; i < num_devices; i++) {
zram = &zram_devices[i];
get_disk(zram->disk);
destroy_device(zram);
zram_reset_device(zram);
put_disk(zram->disk);
}
unregister_blkdev(zram_major, "zram");