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>

diff --git a/drivers/target/target_core_pr.c b/drivers/target/target_core_pr.c
index 2f5d779..3013287 100644 (file)
--- 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;
 }