Dereferencing shost from scsi_exit_rq() is not safe because the
SCSI host may already have been freed when scsi_exit_rq() is
called. Increasing the shost reference count in scsi_init_rq()
and dropping that reference in scsi_exit_rq() is nontrivial since
scsi_host_dev_release() may sleep and since scsi_exit_rq() may
be called from interrupt context. Since scsi_exit_rq() only needs
a single bit from shost, copy that bit into struct scsi_cmnd.
Reported-by: Scott Bauer <scott.bauer@xxxxxxxxx>
Fixes: e9c787e65c0c ("scsi: allocate scsi_cmnd structures as part of struct request")
Signed-off-by: Bart Van Assche <bart.vanassche@xxxxxxxxxxx>
Cc: Scott Bauer <scott.bauer@xxxxxxxxx>
Cc: Christoph Hellwig <hch@xxxxxx>
Cc: Jan Kara <jack@xxxxxxx>
Cc: Hannes Reinecke <hare@xxxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx>
---
drivers/scsi/scsi_lib.c | 39 +++++++++++++++++++++------------------
include/scsi/scsi_cmnd.h | 1 +
2 files changed, 22 insertions(+), 18 deletions(-)
diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c
index 15c9fe766071..3a5a49e3274a 100644
--- a/drivers/scsi/scsi_lib.c
+++ b/drivers/scsi/scsi_lib.c
@@ -43,23 +43,23 @@ static struct kmem_cache *scsi_sense_isadma_cache;
static DEFINE_MUTEX(scsi_sense_cache_mutex);
static inline struct kmem_cache *
-scsi_select_sense_cache(struct Scsi_Host *shost)
+scsi_select_sense_cache(bool unchecked_isa_dma)
{
- return shost->unchecked_isa_dma ?
- scsi_sense_isadma_cache : scsi_sense_cache;
+ return unchecked_isa_dma ? scsi_sense_isadma_cache : scsi_sense_cache;
}
-static void scsi_free_sense_buffer(struct Scsi_Host *shost,
- unsigned char *sense_buffer)
+static void scsi_free_sense_buffer(bool unchecked_isa_dma,
+ unsigned char *sense_buffer)
{
- kmem_cache_free(scsi_select_sense_cache(shost), sense_buffer);
+ kmem_cache_free(scsi_select_sense_cache(unchecked_isa_dma),
+ sense_buffer);
}
-static unsigned char *scsi_alloc_sense_buffer(struct Scsi_Host *shost,
+static unsigned char *scsi_alloc_sense_buffer(bool unchecked_isa_dma,
gfp_t gfp_mask, int numa_node)
{
- return kmem_cache_alloc_node(scsi_select_sense_cache(shost), gfp_mask,
- numa_node);
+ return kmem_cache_alloc_node(scsi_select_sense_cache(unchecked_isa_dma),
+ gfp_mask, numa_node);
}
int scsi_init_sense_cache(struct Scsi_Host *shost)
@@ -67,7 +67,7 @@ int scsi_init_sense_cache(struct Scsi_Host *shost)
struct kmem_cache *cache;
int ret = 0;
- cache = scsi_select_sense_cache(shost);
+ cache = scsi_select_sense_cache(shost->unchecked_isa_dma);
if (cache)
return 0;
@@ -2004,10 +2004,12 @@ static int scsi_init_request(void *data, struct request *rq,
unsigned int numa_node)
{
struct Scsi_Host *shost = data;
+ const bool unchecked_isa_dma = shost->unchecked_isa_dma;
struct scsi_cmnd *cmd = blk_mq_rq_to_pdu(rq);
- cmd->sense_buffer =
- scsi_alloc_sense_buffer(shost, GFP_KERNEL, numa_node);
+ cmd->unchecked_isa_dma = unchecked_isa_dma;
+ cmd->sense_buffer = scsi_alloc_sense_buffer(unchecked_isa_dma,
+ GFP_KERNEL, numa_node);
if (!cmd->sense_buffer)
return -ENOMEM;
cmd->req.sense = cmd->sense_buffer;
@@ -2017,10 +2019,9 @@ static int scsi_init_request(void *data, struct request *rq,
static void scsi_exit_request(void *data, struct request *rq,
unsigned int hctx_idx, unsigned int request_idx)
{
- struct Scsi_Host *shost = data;
struct scsi_cmnd *cmd = blk_mq_rq_to_pdu(rq);
- scsi_free_sense_buffer(shost, cmd->sense_buffer);
+ scsi_free_sense_buffer(cmd->unchecked_isa_dma, cmd->sense_buffer);
}
static int scsi_map_queues(struct blk_mq_tag_set *set)
@@ -2093,11 +2094,14 @@ EXPORT_SYMBOL_GPL(__scsi_init_queue);
static int scsi_init_rq(struct request_queue *q, struct request *rq, gfp_t gfp)
{
struct Scsi_Host *shost = q->rq_alloc_data;
+ const bool unchecked_isa_dma = shost->unchecked_isa_dma;
struct scsi_cmnd *cmd = blk_mq_rq_to_pdu(rq);
memset(cmd, 0, sizeof(*cmd));
- cmd->sense_buffer = scsi_alloc_sense_buffer(shost, gfp, NUMA_NO_NODE);
+ cmd->unchecked_isa_dma = unchecked_isa_dma;
+ cmd->sense_buffer = scsi_alloc_sense_buffer(unchecked_isa_dma, gfp,
+ NUMA_NO_NODE);
if (!cmd->sense_buffer)
goto fail;
cmd->req.sense = cmd->sense_buffer;
@@ -2111,19 +2115,18 @@ static int scsi_init_rq(struct request_queue *q, struct request *rq, gfp_t gfp)
return 0;
fail_free_sense:
- scsi_free_sense_buffer(shost, cmd->sense_buffer);
+ scsi_free_sense_buffer(unchecked_isa_dma, cmd->sense_buffer);
fail:
return -ENOMEM;
}
static void scsi_exit_rq(struct request_queue *q, struct request *rq)
{
- struct Scsi_Host *shost = q->rq_alloc_data;
struct scsi_cmnd *cmd = blk_mq_rq_to_pdu(rq);
if (cmd->prot_sdb)
kmem_cache_free(scsi_sdb_cache, cmd->prot_sdb);
- scsi_free_sense_buffer(shost, cmd->sense_buffer);
+ scsi_free_sense_buffer(cmd->unchecked_isa_dma, cmd->sense_buffer);
}
struct request_queue *scsi_alloc_queue(struct scsi_device *sdev)
diff --git a/include/scsi/scsi_cmnd.h b/include/scsi/scsi_cmnd.h
index b379f93a2c48..9f1b5432c4c1 100644
--- a/include/scsi/scsi_cmnd.h
+++ b/include/scsi/scsi_cmnd.h
@@ -139,6 +139,7 @@ struct scsi_cmnd {
int result; /* Status code from lower level driver */
int flags; /* Command flags */
+ bool unchecked_isa_dma;
unsigned char tag; /* SCSI-II queued command tag */
};
--
2.12.2
