[PATCH 05/21] uas: Do not use scsi_host_find_tag

Hans de Goede
2014-09-10T11:47:03Z

Using scsi_host_find_tag with tags returned by the device is unsafe for
multiple reasons:

1) It returns tags->rqs[tag], which may be non NULL even when the cmnd is
not owned by us
2) It returns tags->rqs[tag], without holding any locks protecting it
3) It returns tags->rqs[tag], without doing any boundary checking

Instead keep our own list which maps tags -> inflight cmnds.

Signed-off-by: Hans de Goede <hdegoede@redhat.com>
---
drivers/usb/storage/uas.c | 39 ++++++++++++++++++---------------------
1 file changed, 18 insertions(+), 21 deletions(-)

diff --git a/drivers/usb/storage/uas.c b/drivers/usb/storage/uas.c
index 05c1c81..b2423d3 100644
--- a/drivers/usb/storage/uas.c
+++ b/drivers/usb/storage/uas.c
@@ -29,6 +29,8 @@

#include "uas-detect.h"

+#define MAX_CMNDS 256
+
/*
* The r00-r01c specs define this version of the SENSE IU data structure.
* It's still in use by several different firmware releases.
@@ -54,7 +56,7 @@ struct uas_dev_info {
unsigned use_streams:1;
unsigned uas_sense_old:1;
unsigned shutdown:1;
- struct scsi_cmnd *cmnd;
+ struct scsi_cmnd *cmnd[MAX_CMNDS];
spinlock_t lock;
struct work_struct work;
struct list_head inflight_list;
@@ -314,6 +316,7 @@ static int uas_try_complete(struct scsi_cmnd *cmnd, const char *caller)
if (cmdinfo->state & COMMAND_ABORTED)
scmd_printk(KERN_INFO, cmnd, "abort completed\n");
list_del(&cmdinfo->list);
+ devinfo->cmnd[uas_get_tag(cmnd) - 1] = NULL;
cmnd->scsi_done(cmnd);
return 0;
}
@@ -339,7 +342,7 @@ static void uas_stat_cmplt(struct urb *urb)
struct scsi_cmnd *cmnd;
struct uas_cmd_info *cmdinfo;
unsigned long flags;
- u16 tag;
+ unsigned int idx;

spin_lock_irqsave(&devinfo->lock, flags);

@@ -357,21 +360,17 @@ static void uas_stat_cmplt(struct urb *urb)
goto out;
}

- tag = be16_to_cpup(&iu->tag) - 1;
- if (tag == 0)
- cmnd = devinfo->cmnd;
- else
- cmnd = scsi_host_find_tag(shost, tag - 1);
-
- if (!cmnd)
+ idx = be16_to_cpup(&iu->tag) - 1;
+ if (idx >= MAX_CMNDS || !devinfo->cmnd[idx]) {
+ dev_err(&urb->dev->dev,
+ "stat urb: no pending cmd for tag %d\n", idx + 1);
goto out;
+ }

+ cmnd = devinfo->cmnd[idx];
cmdinfo = (void *)&cmnd->SCp;
switch (iu->iu_id) {
case IU_ID_STATUS:
- if (devinfo->cmnd == cmnd)
- devinfo->cmnd = NULL;
-
if (urb->actual_length < 16)
devinfo->uas_sense_old = 1;
if (devinfo->uas_sense_old)
@@ -672,6 +671,7 @@ static int uas_queuecommand_lck(struct scsi_cmnd *cmnd,
struct uas_dev_info *devinfo = sdev->hostdata;
struct uas_cmd_info *cmdinfo = (void *)&cmnd->SCp;
unsigned long flags;
+ unsigned int stream;
int err;

BUILD_BUG_ON(sizeof(struct uas_cmd_info) > sizeof(struct scsi_pointer));
@@ -685,19 +685,16 @@ static int uas_queuecommand_lck(struct scsi_cmnd *cmnd,
return 0;
}

- if (devinfo->cmnd) {
+ stream = uas_get_tag(cmnd);
+ if (devinfo->cmnd[stream - 1]) {
spin_unlock_irqrestore(&devinfo->lock, flags);
return SCSI_MLQUEUE_DEVICE_BUSY;
}

- memset(cmdinfo, 0, sizeof(*cmdinfo));
-
- if (!blk_rq_tagged(cmnd->request))
- devinfo->cmnd = cmnd;
-
cmnd->scsi_done = done;

- cmdinfo->stream = uas_get_tag(cmnd);
+ memset(cmdinfo, 0, sizeof(*cmdinfo));
+ cmdinfo->stream = stream;
cmdinfo->state = SUBMIT_STATUS_URB | ALLOC_CMD_URB | SUBMIT_CMD_URB;

switch (cmnd->sc_data_direction) {
@@ -727,6 +724,7 @@ static int uas_queuecommand_lck(struct scsi_cmnd *cmnd,
uas_add_work(cmdinfo);
}

+ devinfo->cmnd[stream - 1] = cmnd;
list_add_tail(&cmdinfo->list, &devinfo->inflight_list);
spin_unlock_irqrestore(&devinfo->lock, flags);
return 0;
@@ -862,7 +860,6 @@ static int uas_configure_endpoints(struct uas_dev_info *devinfo)
int r;

devinfo->uas_sense_old = 0;
- devinfo->cmnd = NULL;

r = uas_find_endpoints(devinfo->intf->cur_altsetting, eps);
if (r)
@@ -882,7 +879,7 @@ static int uas_configure_endpoints(struct uas_dev_info *devinfo)
devinfo->use_streams = 0;
} else {
devinfo->qdepth = usb_alloc_streams(devinfo->intf, eps + 1,
- 3, 256, GFP_NOIO);
+ 3, MAX_CMNDS, GFP_NOIO);
if (devinfo->qdepth < 0)
return devinfo->qdepth;
devinfo->use_streams = 1;
--
2.1.0