When scsi_init_sense_cache(host) is called concurrently from different
hosts, each code path may see that the cache isn't created, then try
to create a new one, then the created sense cache may be overrided and
leaked.

Fixes the issue by moving 'mutex_lock(&scsi_sense_cache_mutex)' before
scsi_select_sense_cache().

Cc: Ewan D. Milne <emi...@redhat.com>
Signed-off-by: Ming Lei <ming....@redhat.com>
---
 drivers/scsi/scsi_lib.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c
index e07a376a8c38..7493680ec104 100644
--- a/drivers/scsi/scsi_lib.c
+++ b/drivers/scsi/scsi_lib.c
@@ -72,11 +72,11 @@ int scsi_init_sense_cache(struct Scsi_Host *shost)
        struct kmem_cache *cache;
        int ret = 0;
 
+       mutex_lock(&scsi_sense_cache_mutex);
        cache = scsi_select_sense_cache(shost->unchecked_isa_dma);
        if (cache)
-               return 0;
+               goto exit;
 
-       mutex_lock(&scsi_sense_cache_mutex);
        if (shost->unchecked_isa_dma) {
                scsi_sense_isadma_cache =
                        kmem_cache_create("scsi_sense_cache(DMA)",
@@ -92,7 +92,7 @@ int scsi_init_sense_cache(struct Scsi_Host *shost)
                if (!scsi_sense_cache)
                        ret = -ENOMEM;
        }
-
+ exit:
        mutex_unlock(&scsi_sense_cache_mutex);
        return ret;
 }
-- 
2.20.1

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