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zram: avoid invalid memory access in zram_exit()

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commit 6030ea9b35 upstream.

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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
[bwh: Backported to 3.2: adjust context]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
Cc: Jianguo Wu <wujianguo@huawei.com>
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 74eb879bd0
commit 5e84bf6dca
1 changed files with 2 additions and 0 deletions
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2
drivers/staging/zram/zram_drv.c
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@ -841,9 +841,11 @@ static void __exit zram_exit(void)
for (i = 0; i < num_devices; i++) {
zram = &zram_devices[i];
get_disk(zram->disk);
destroy_device(zram);
if (zram->init_done)
zram_reset_device(zram);
put_disk(zram->disk);
}
unregister_blkdev(zram_major, "zram");