The change is similar to that is used in comp_algorithm_set.
default_compressor is used for ZRAM_PRIMARY_COMP only, but if
CONFIG_ZRAM_MULTI_COMP isn't set, then ZRAM_PRIMARY_COMP and
ZRAM_SECONDARY_COMP are the same.

This is detected by KASAN.

==================================================================
 Call trace:
  kfree+0x60/0x3a0
  zram_destroy_comps+0x98/0x198 [zram]
  zram_reset_device+0x22c/0x4a8 [zram]
  reset_store+0x1bc/0x2d8 [zram]
  dev_attr_store+0x44/0x80
  sysfs_kf_write+0xfc/0x188
  kernfs_fop_write_iter+0x28c/0x428
  vfs_write+0x4dc/0x9b8
  ksys_write+0x100/0x1f8
  __arm64_sys_write+0x74/0xb8
  invoke_syscall+0xd8/0x260
  el0_svc_common.constprop.0+0xb4/0x240
  do_el0_svc+0x48/0x68
  el0_svc+0x40/0xc8
  el0t_64_sync_handler+0x120/0x130
  el0t_64_sync+0x190/0x198
==================================================================

Signed-off-by: Andrey Skvortsov <andrej.skvortzov@gmail.com>
Fixes: 684826f8271a ("zram: free secondary algorithms names")
Cc: <stable@vger.kernel.org>
---

Changes in v2:
 - removed comment from source code about freeing statically defined compression
 - removed part of KASAN report from commit description
 - added information about CONFIG_ZRAM_MULTI_COMP into commit description

 drivers/block/zram/zram_drv.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/block/zram/zram_drv.c b/drivers/block/zram/zram_drv.c
index c3d245617083d..4a9cdb7fe8878 100644
--- a/drivers/block/zram/zram_drv.c
+++ b/drivers/block/zram/zram_drv.c
@@ -2116,7 +2116,8 @@ static void zram_destroy_comps(struct zram *zram)
 	}
 
 	for (prio = ZRAM_SECONDARY_COMP; prio < ZRAM_MAX_COMPS; prio++) {
-		kfree(zram->comp_algs[prio]);
+		if (zram->comp_algs[prio] != default_compressor)
+			kfree(zram->comp_algs[prio]);
 		zram->comp_algs[prio] = NULL;
 	}
 
-- 
2.45.2

On (24/09/23 19:11), Andrey Skvortsov wrote:
> The change is similar to that is used in comp_algorithm_set.
> default_compressor is used for ZRAM_PRIMARY_COMP only, but if
> CONFIG_ZRAM_MULTI_COMP isn't set, then ZRAM_PRIMARY_COMP and
> ZRAM_SECONDARY_COMP are the same.
> 
> This is detected by KASAN.
> 
> ==================================================================
>  Call trace:
>   kfree+0x60/0x3a0
>   zram_destroy_comps+0x98/0x198 [zram]
>   zram_reset_device+0x22c/0x4a8 [zram]
>   reset_store+0x1bc/0x2d8 [zram]
>   dev_attr_store+0x44/0x80
>   sysfs_kf_write+0xfc/0x188
>   kernfs_fop_write_iter+0x28c/0x428
>   vfs_write+0x4dc/0x9b8
>   ksys_write+0x100/0x1f8
>   __arm64_sys_write+0x74/0xb8
>   invoke_syscall+0xd8/0x260
>   el0_svc_common.constprop.0+0xb4/0x240
>   do_el0_svc+0x48/0x68
>   el0_svc+0x40/0xc8
>   el0t_64_sync_handler+0x120/0x130
>   el0t_64_sync+0x190/0x198
> ==================================================================
> 
> Signed-off-by: Andrey Skvortsov <andrej.skvortzov@gmail.com>
> Fixes: 684826f8271a ("zram: free secondary algorithms names")
> Cc: <stable@vger.kernel.org>

Reviewed-by: Sergey Senozhatsky <senozhatsky@chromium.org>