[PATCH v2 17/19] qla2xxx: prevent bounds-check bypass via speculative execution

[Dan Williams]

Static analysis reports that 'handle' may be a user controlled value
that is used as a data dependency to read 'sp' from the
'req->outstanding_cmds' array.  In order to avoid potential leaks of
kernel memory values, block speculative execution of the instruction
stream that could issue reads based on an invalid value of 'sp'. In this
case 'sp' is directly dereferenced later in the function.

If completion tags can be specified by userspace or otherwise
controlled, we should sanitize 'handle' with array_ptr.

Based on an original patch by Elena Reshetova.

Cc: qla2xxx-upstr...@qlogic.com
Cc: "James E.J. Bottomley" <j...@linux.vnet.ibm.com>
Cc: "Martin K. Petersen" <martin.peter...@oracle.com>
Cc: linux-scsi@vger.kernel.org
Signed-off-by: Elena Reshetova <elena.reshet...@intel.com>
Signed-off-by: Dan Williams <dan.j.willi...@intel.com>
---
 drivers/scsi/qla2xxx/qla_mr.c |   17 +++++++++++------
 1 file changed, 11 insertions(+), 6 deletions(-)

diff --git a/drivers/scsi/qla2xxx/qla_mr.c b/drivers/scsi/qla2xxx/qla_mr.c
index d5da3981cefe..6de3f0fddcfc 100644
--- a/drivers/scsi/qla2xxx/qla_mr.c
+++ b/drivers/scsi/qla2xxx/qla_mr.c
@@ -9,6 +9,7 @@
 #include <linux/ktime.h>
 #include <linux/pci.h>
 #include <linux/ratelimit.h>
+#include <linux/nospec.h>
 #include <linux/vmalloc.h>
 #include <linux/bsg-lib.h>
 #include <scsi/scsi_tcq.h>
@@ -2275,7 +2276,7 @@ qlafx00_ioctl_iosb_entry(scsi_qla_host_t *vha, struct 
req_que *req,
 static void
 qlafx00_status_entry(scsi_qla_host_t *vha, struct rsp_que *rsp, void *pkt)
 {
-       srb_t           *sp;
+       srb_t           *sp, **elem;
        fc_port_t       *fcport;
        struct scsi_cmnd *cp;
        struct sts_entry_fx00 *sts;
@@ -2304,8 +2305,10 @@ qlafx00_status_entry(scsi_qla_host_t *vha, struct 
rsp_que *rsp, void *pkt)
        req = ha->req_q_map[que];
 
        /* Validate handle. */
-       if (handle < req->num_outstanding_cmds)
-               sp = req->outstanding_cmds[handle];
+       elem = array_ptr(req->outstanding_cmds, handle,
+                       req->num_outstanding_cmds);
+       if (elem)
+               sp = *elem;
        else
                sp = NULL;
 
@@ -2626,7 +2629,7 @@ static void
 qlafx00_multistatus_entry(struct scsi_qla_host *vha,
        struct rsp_que *rsp, void *pkt)
 {
-       srb_t           *sp;
+       srb_t           *sp, **elem;
        struct multi_sts_entry_fx00 *stsmfx;
        struct qla_hw_data *ha = vha->hw;
        uint32_t handle, hindex, handle_count, i;
@@ -2655,8 +2658,10 @@ qlafx00_multistatus_entry(struct scsi_qla_host *vha,
                req = ha->req_q_map[que];
 
                /* Validate handle. */
-               if (handle < req->num_outstanding_cmds)
-                       sp = req->outstanding_cmds[handle];
+               elem = array_ptr(req->outstanding_cmds, handle,
+                               req->num_outstanding_cmds);
+               if (elem)
+                       sp = *elem;
                else
                        sp = NULL;