| From | Greg Kroah-Hartman <> | Subject | [PATCH 3.4 103/214] zram: avoid invalid memory access in zram_exit() | Date | Wed, 4 Jun 2014 21:17:46 -0700 |
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3.4-stable review patch. If anyone has any objections, please let me know.
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From: Jiang Liu <liuj97@gmail.com>
commit 6030ea9b35971a4200062f010341ab832e878ac9 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>
--- drivers/staging/zram/zram_drv.c | 2 ++ 1 file changed, 2 insertions(+)
--- a/drivers/staging/zram/zram_drv.c +++ b/drivers/staging/zram/zram_drv.c @@ -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");
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