[PATCH 4.12 045/196] scsi: Avoid that scsi_exit_rq() triggers a use-after-free

[Greg Kroah-Hartman]

4.12-stable review patch.  If anyone has any objections, please let me know.

--

From: Bart Van Assche 

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 
Fixes: e9c787e65c0c ("scsi: allocate scsi_cmnd structures as part of struct 
request")
Signed-off-by: Bart Van Assche 
Reviewed-by: Christoph Hellwig 
Cc: Hannes Reinecke 
Cc: Scott Bauer 
Cc: Jan Kara 
Signed-off-by: Martin K. Petersen 
Signed-off-by: Greg Kroah-Hartman 

---
 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(>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 @@ 

[PATCH 4.12 045/196] scsi: Avoid that scsi_exit_rq() triggers a use-after-free

[Greg Kroah-Hartman]

4.12-stable review patch.  If anyone has any objections, please let me know.

--

From: Bart Van Assche 

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 
Fixes: e9c787e65c0c ("scsi: allocate scsi_cmnd structures as part of struct 
request")
Signed-off-by: Bart Van Assche 
Reviewed-by: Christoph Hellwig 
Cc: Hannes Reinecke 
Cc: Scott Bauer 
Cc: Jan Kara 
Signed-off-by: Martin K. Petersen 
Signed-off-by: Greg Kroah-Hartman 

---
 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(>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 =