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scsi: core: Fix race on creating sense cache

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When scsi_init_sense_cache(host) is called concurrently from different
hosts, each code path may find that no cache has been created and
allocate a new one. The lack of locking can lead to potentially
overriding a cache allocated by a different host.

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

Fixes: 0a6ac4ee7c ("scsi: respect unchecked_isa_dma for blk-mq")
Cc: Stable <stable@vger.kernel.org>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Hannes Reinecke <hare@suse.com>
Cc: Ewan D. Milne <emilne@redhat.com>
Signed-off-by: Ming Lei <ming.lei@redhat.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
This commit is contained in:
Ming Lei 2019-07-12 10:08:19 +08:00 committed by Martin K. Petersen
parent 0cdc58580b
commit f9b0530fa0
1 changed files with 3 additions and 3 deletions
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6
drivers/scsi/scsi_lib.c
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@ -84,11 +84,11 @@ 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)",
@ -104,7 +104,7 @@ int scsi_init_sense_cache(struct Scsi_Host *shost)
if (!scsi_sense_cache)
ret = -ENOMEM;
}
exit:
mutex_unlock(&scsi_sense_cache_mutex);
return ret;
}