[PATCH 6.6.y 4/4] zram: set default primary compressor in zram_destroy_comps()

From: Sergey Senozhatsky <senozhatsky@chromium.org>

[ Upstream commit dde75313eed0b014c437f48dd75c0308b592cbf9 ]

Patch series "zram: fix zram issues reported by sashiko".

Sashiko drove by and reported [1] a couple of zram issues:
a possible BUG_ON() in zlib code due to missing winbits range
validation and one possible NULL-ptr dereference in zcomp.
Both are low risk yet still worth fixing.

This patch (of 2):

zram_destroy_comps() resets all compressors and leaves them set to NULL,
including the primary one, which is invalid device state, as now
comp_algorithm_show()->strcmp() can be called on a NULL compressor.  Set
default primary compressor in zram_destroy_comps().

Link: https://lore.kernel.org/20260729045745.775973-2-senozhatsky@chromium.org (local)
Fixes: 486fd58af7ac ("zram: don't free statically defined names")
Link: https://sashiko.dev/#/patchset/20260728092935.31139-1-haoqinhuang7@gmail.com [1]
Signed-off-by: Sergey Senozhatsky <senozhatsky@chromium.org>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Haoqin Huang <redacted>
Cc: <redacted>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 drivers/block/zram/zram_drv.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/drivers/block/zram/zram_drv.c b/drivers/block/zram/zram_drv.c
index 6a4870cf6e590..d7d4e39530392 100644
--- a/drivers/block/zram/zram_drv.c
+++ b/drivers/block/zram/zram_drv.c

@@ -2031,6 +2031,7 @@ static void zram_destroy_comps(struct zram *zram)
 	}
 
 	zram_comp_params_reset(zram);
+	comp_algorithm_set(zram, ZRAM_PRIMARY_COMP, default_compressor);
 }
 #undef zram_comp_params_reset
 

@@ -2049,8 +2050,6 @@ static void zram_reset_device(struct zram *zram)
 	zram_destroy_comps(zram);
 	memset(&zram->stats, 0, sizeof(zram->stats));
 	reset_bdev(zram);
-
-	comp_algorithm_set(zram, ZRAM_PRIMARY_COMP, default_compressor);
 }
 
 static ssize_t disksize_store(struct device *dev,

-- 
2.53.0