zram: check comp is non-NULL before calling comp_destroy

This is a pre-requisite for the backport of commit 74363ec674cb ("zram:
fix uninitialized ZRAM not releasing backing device"), which has been
implemented differently in commit 7ac07a26dea7 ("zram: preparation for
multi-zcomp support") upstream.

We only need to ensure that zcomp_destroy is not called with a NULL
comp, so add this check as the other commit cannot be backported easily.

Stable-dep-of: 74363ec674cb ("zram: fix uninitialized ZRAM not releasing backing device")
Link: https://lore.kernel.org/Z3ytcILx4S1v_ueJ@codewreck.org
Suggested-by: Kairui Song <kasong@tencent.com>
Signed-off-by: Dominique Martinet <dominique.martinet@atmark-techno.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/block/zram/zram_drv.c b/drivers/block/zram/zram_drv.c
index b83181357f36d10c26f598fe36da5655a5618180..b4133258e1bfde67d7d9e546ac8d342f05615f64 100644 (file)
--- a/drivers/block/zram/zram_drv.c
+++ b/drivers/block/zram/zram_drv.c
@@ -1733,7 +1733,8 @@ static void zram_reset_device(struct zram *zram)
        zram_meta_free(zram, zram->disksize);
        zram->disksize = 0;
        memset(&zram->stats, 0, sizeof(zram->stats));
-       zcomp_destroy(zram->comp);
+       if (zram->comp)
+               zcomp_destroy(zram->comp);
        zram->comp = NULL;
        reset_bdev(zram);