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scsi: Avoid that scsi_exit_rq() triggers a use-after-free 

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@intel.com>
Fixes: e9c787e65c ("scsi: allocate scsi_cmnd structures as part of struct request")
Signed-off-by: Bart Van Assche <bart.vanassche@sandisk.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Cc: Hannes Reinecke <hare@suse.com>
Cc: Scott Bauer <scott.bauer@intel.com>
Cc: Jan Kara <jack@suse.cz>
Cc: <stable@vger.kernel.org>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
This commit is contained in:
Bart Van Assche 2017-06-02 14:21:52 -07:00 committed by Martin K. Petersen
parent 896f6966fc
commit 8e6882545d
2 changed files with 30 additions and 18 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

47
drivers/scsi/scsi_lib.c
View File

@ -45,23 +45,23 @@ 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)
@ -69,7 +69,7 @@ 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;
@ -1138,6 +1138,7 @@ void scsi_init_command(struct scsi_device *dev, struct scsi_cmnd *cmd)
{
void *buf = cmd->sense_buffer;
void *prot = cmd->prot_sdb;
unsigned int unchecked_isa_dma = cmd->flags & SCMD_UNCHECKED_ISA_DMA;
unsigned long flags;
/* zero out the cmd, except for the embedded scsi_request */
@ -1147,6 +1148,7 @@ void scsi_init_command(struct scsi_device *dev, struct scsi_cmnd *cmd)
cmd->device = dev;
cmd->sense_buffer = buf;
cmd->prot_sdb = prot;
cmd->flags = unchecked_isa_dma;
INIT_DELAYED_WORK(&cmd->abort_work, scmd_eh_abort_handler);
cmd->jiffies_at_alloc = jiffies;
@ -1847,6 +1849,7 @@ static int scsi_mq_prep_fn(struct request *req)
struct scsi_device *sdev = req->q->queuedata;
struct Scsi_Host *shost = sdev->host;
unsigned char *sense_buf = cmd->sense_buffer;
unsigned int unchecked_isa_dma = cmd->flags & SCMD_UNCHECKED_ISA_DMA;
struct scatterlist *sg;
/* zero out the cmd, except for the embedded scsi_request */
@ -1858,6 +1861,7 @@ static int scsi_mq_prep_fn(struct request *req)
cmd->request = req;
cmd->device = sdev;
cmd->sense_buffer = sense_buf;
cmd->flags = unchecked_isa_dma;
cmd->tag = req->tag;
@ -2004,10 +2008,13 @@ static int scsi_init_request(struct blk_mq_tag_set *set, struct request *rq,
unsigned int hctx_idx, unsigned int numa_node)
{
struct Scsi_Host *shost = set->driver_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);
if (unchecked_isa_dma)
cmd->flags |= SCMD_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 +2024,10 @@ static int scsi_init_request(struct blk_mq_tag_set *set, struct request *rq,
static void scsi_exit_request(struct blk_mq_tag_set *set, struct request *rq,
unsigned int hctx_idx)
{
struct Scsi_Host *shost = set->driver_data;
struct scsi_cmnd *cmd = blk_mq_rq_to_pdu(rq);
scsi_free_sense_buffer(shost, cmd->sense_buffer);
scsi_free_sense_buffer(cmd->flags & SCMD_UNCHECKED_ISA_DMA,
cmd->sense_buffer);
}
static int scsi_map_queues(struct blk_mq_tag_set *set)
@ -2093,11 +2100,15 @@ 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);
if (unchecked_isa_dma)
cmd->flags |= SCMD_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 +2122,19 @@ 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->flags & SCMD_UNCHECKED_ISA_DMA,
cmd->sense_buffer);
}
struct request_queue *scsi_alloc_queue(struct scsi_device *sdev)

1
include/scsi/scsi_cmnd.h
View File

@ -56,6 +56,7 @@ struct scsi_pointer {
/* for scmd->flags */
#define SCMD_TAGGED (1 << 0)
#define SCMD_UNCHECKED_ISA_DMA (1 << 1)
struct scsi_cmnd {
struct scsi_request req;