This is a note to let you know that I've just added the patch titled
scsi: Avoid that scsi_exit_rq() triggers a use-after-free
to the 4.12-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
scsi-avoid-that-scsi_exit_rq-triggers-a-use-after-free.patch
and it can be found in the queue-4.12 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From 8e6882545d8c06f99e9e117741cc87f3338b0bef Mon Sep 17 00:00:00 2001
From: Bart Van Assche <bart.vanassche@xxxxxxxxxxx>
Date: Fri, 2 Jun 2017 14:21:52 -0700
Subject: scsi: Avoid that scsi_exit_rq() triggers a use-after-free
From: Bart Van Assche <bart.vanassche@xxxxxxxxxxx>
commit 8e6882545d8c06f99e9e117741cc87f3338b0bef upstream.
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>
Reviewed-by: Christoph Hellwig <hch@xxxxxx>
Cc: Hannes Reinecke <hare@xxxxxxxx>
Cc: Scott Bauer <scott.bauer@xxxxxxxxx>
Cc: Jan Kara <jack@xxxxxxx>
Signed-off-by: Martin K. Petersen <martin.petersen@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
drivers/scsi/scsi_lib.c | 47 +++++++++++++++++++++++++++++------------------
include/scsi/scsi_cmnd.h | 1 +
2 files changed, 30 insertions(+), 18 deletions(-)
--- a/drivers/scsi/scsi_lib.c
+++ b/drivers/scsi/scsi_lib.c
@@ -45,23 +45,23 @@ static struct kmem_cache *scsi_sense_isa
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_Ho
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_devic
{
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_devic
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 reques
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 reques
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_
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_
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_q
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)
--- a/include/scsi/scsi_cmnd.h
+++ b/include/scsi/scsi_cmnd.h
@@ -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;
Patches currently in stable-queue which might be from bart.vanassche@xxxxxxxxxxx are
queue-4.12/scsi-avoid-that-scsi_exit_rq-triggers-a-use-after-free.patch
queue-4.12/xen-scsiback-fix-a-tmr-related-use-after-free.patch