[PATCH] qed: Fix potential use-after-free in qed_spq_post()

[Roland Dreier]

From: Roland Dreier <rol...@purestorage.com>

We need to check if p_ent->comp_mode is QED_SPQ_MODE_EBLOCK before
calling qed_spq_add_entry().  The test is fine is the mode is EBLOCK,
but if it isn't then qed_spq_add_entry() might kfree(p_ent).

Signed-off-by: Roland Dreier <rol...@purestorage.com>
---
 drivers/net/ethernet/qlogic/qed/qed_spq.c | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/drivers/net/ethernet/qlogic/qed/qed_spq.c 
b/drivers/net/ethernet/qlogic/qed/qed_spq.c
index be48d9abd001..3588081b2e27 100644
--- a/drivers/net/ethernet/qlogic/qed/qed_spq.c
+++ b/drivers/net/ethernet/qlogic/qed/qed_spq.c
@@ -776,6 +776,7 @@ int qed_spq_post(struct qed_hwfn *p_hwfn,
        int rc = 0;
        struct qed_spq *p_spq = p_hwfn ? p_hwfn->p_spq : NULL;
        bool b_ret_ent = true;
+       bool eblock;
 
        if (!p_hwfn)
                return -EINVAL;
@@ -794,6 +795,11 @@ int qed_spq_post(struct qed_hwfn *p_hwfn,
        if (rc)
                goto spq_post_fail;
 
+       /* Check if entry is in block mode before qed_spq_add_entry,
+        * which might kfree p_ent.
+        */
+       eblock = (p_ent->comp_mode == QED_SPQ_MODE_EBLOCK);
+
        /* Add the request to the pending queue */
        rc = qed_spq_add_entry(p_hwfn, p_ent, p_ent->priority);
        if (rc)
@@ -811,7 +817,7 @@ int qed_spq_post(struct qed_hwfn *p_hwfn,
 
        spin_unlock_bh(&p_spq->lock);
 
-       if (p_ent->comp_mode == QED_SPQ_MODE_EBLOCK) {
+       if (eblock) {
                /* For entries in QED BLOCK mode, the completion code cannot
                 * perform the necessary cleanup - if it did, we couldn't
                 * access p_ent here to see whether it's successful or not.
-- 
2.14.1