target: Fix free-after-use regression in PR unregister

This patch addresses a >= v3.11 free-after-use regression
in core_scsi3_emulate_pro_register() that was introduced
in the following commit:

commit bc118fe4c4a8cfa453491ba77c0a146a6d0e73e0
Author: Andy Grover <agrover@redhat.com>
Date:   Thu May 16 10:41:04 2013 -0700

    target: Further refactoring of core_scsi3_emulate_pro_register()

To avoid the free-after-use, save an type value before hand, and
only call core_scsi3_put_pr_reg() with a valid *pr_reg.

Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Cc: Andy Grover <agrover@redhat.com>
Cc: <stable@vger.kernel.org> #3.11+
Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>

1 files changed, 7 insertions, 4 deletions

diff --git a/drivers/target/target_core_pr.c b/drivers/target/target_core_pr.c
index 2f5d77932c80..3013287a2aaa 100644
--- a/drivers/target/target_core_pr.c
+++ b/drivers/target/target_core_pr.c
@@ -2009,7 +2009,7 @@ core_scsi3_emulate_pro_register(struct se_cmd *cmd, u64 res_key, u64 sa_res_key,
         struct t10_reservation *pr_tmpl = &dev->t10_pr;
         unsigned char isid_buf[PR_REG_ISID_LEN], *isid_ptr = NULL;
         sense_reason_t ret = TCM_NO_SENSE;
-        int pr_holder = 0;
+        int pr_holder = 0, type;
 
         if (!se_sess || !se_lun) {
                 pr_err("SPC-3 PR: se_sess || struct se_lun is NULL!\n");
@@ -2131,6 +2131,7 @@ core_scsi3_emulate_pro_register(struct se_cmd *cmd, u64 res_key, u64 sa_res_key,
                         ret = TCM_RESERVATION_CONFLICT;
                         goto out;
                 }
+                type = pr_reg->pr_res_type;
 
                 spin_lock(&pr_tmpl->registration_lock);
                 /*
@@ -2161,6 +2162,7 @@ core_scsi3_emulate_pro_register(struct se_cmd *cmd, u64 res_key, u64 sa_res_key,
                  * Release the calling I_T Nexus registration now..
                  */
                 __core_scsi3_free_registration(cmd->se_dev, pr_reg, NULL, 1);
+                pr_reg = NULL;
 
                 /*
                  * From spc4r17, section 5.7.11.3 Unregistering
@@ -2174,8 +2176,8 @@ core_scsi3_emulate_pro_register(struct se_cmd *cmd, u64 res_key, u64 sa_res_key,
                  * RESERVATIONS RELEASED.
                  */
                 if (pr_holder &&
-                    (pr_reg->pr_res_type == PR_TYPE_WRITE_EXCLUSIVE_REGONLY ||
-                     pr_reg->pr_res_type == PR_TYPE_EXCLUSIVE_ACCESS_REGONLY)) {
+                    (type == PR_TYPE_WRITE_EXCLUSIVE_REGONLY ||
+                     type == PR_TYPE_EXCLUSIVE_ACCESS_REGONLY)) {
                         list_for_each_entry(pr_reg_p,
                                         &pr_tmpl->registration_list,
                                         pr_reg_list) {
@@ -2194,7 +2196,8 @@ core_scsi3_emulate_pro_register(struct se_cmd *cmd, u64 res_key, u64 sa_res_key,
         ret = core_scsi3_update_and_write_aptpl(dev, aptpl);
 
 out:
-        core_scsi3_put_pr_reg(pr_reg);
+        if (pr_reg)
+                core_scsi3_put_pr_reg(pr_reg);
         return ret;
 }