[PATCH] [v2] qed: Fix a potential use-after-free in qed_cxt_tables_alloc

[Dinghao Liu]

qed_ilt_shadow_alloc() will call qed_ilt_shadow_free() to
free p_hwfn->p_cxt_mngr->ilt_shadow on error. However,
qed_cxt_tables_alloc() accesses the freed pointer on failure
of qed_ilt_shadow_alloc() through calling qed_cxt_mngr_free(),
which may lead to use-after-free. Fix this issue by setting
p_hwfn->p_cxt_mngr->ilt_shadow to NULL in qed_ilt_shadow_free().

Fixes: fe56b9e6a8d9 ("qed: Add module with basic common support")
Signed-off-by: Dinghao Liu <dinghao.liu@xxxxxxxxxx>
---

Changelog:

v2: -Change the bug type from double-free to use-after-free.
    -Move the null check against p_mngr->ilt_shadow to the beginning
     of the function qed_ilt_shadow_free().
    -When kcalloc() fails in qed_ilt_shadow_alloc(), just return
     because there is nothing to free.
---
 drivers/net/ethernet/qlogic/qed/qed_cxt.c | 12 +++++++-----
 1 file changed, 7 insertions(+), 5 deletions(-)

diff --git a/drivers/net/ethernet/qlogic/qed/qed_cxt.c b/drivers/net/ethernet/qlogic/qed/qed_cxt.c
index 65e20693c549..911e0c0d3563 100644
--- a/drivers/net/ethernet/qlogic/qed/qed_cxt.c
+++ b/drivers/net/ethernet/qlogic/qed/qed_cxt.c
@@ -921,9 +921,12 @@ static void qed_ilt_shadow_free(struct qed_hwfn *p_hwfn)
 	struct qed_cxt_mngr *p_mngr = p_hwfn->p_cxt_mngr;
 	u32 ilt_size, i;
 
+	if (!p_mngr->ilt_shadow)
+		return;
+
 	ilt_size = qed_cxt_ilt_shadow_size(p_cli);
 
-	for (i = 0; p_mngr->ilt_shadow && i < ilt_size; i++) {
+	for (i = 0; i < ilt_size; i++) {
 		struct phys_mem_desc *p_dma = &p_mngr->ilt_shadow[i];
 
 		if (p_dma->virt_addr)
@@ -933,6 +936,7 @@ static void qed_ilt_shadow_free(struct qed_hwfn *p_hwfn)
 		p_dma->virt_addr = NULL;
 	}
 	kfree(p_mngr->ilt_shadow);
+	p_hwfn->p_cxt_mngr->ilt_shadow = NULL;
 }
 
 static int qed_ilt_blk_alloc(struct qed_hwfn *p_hwfn,
@@ -995,10 +999,8 @@ static int qed_ilt_shadow_alloc(struct qed_hwfn *p_hwfn)
 	size = qed_cxt_ilt_shadow_size(clients);
 	p_mngr->ilt_shadow = kcalloc(size, sizeof(struct phys_mem_desc),
 				     GFP_KERNEL);
-	if (!p_mngr->ilt_shadow) {
-		rc = -ENOMEM;
-		goto ilt_shadow_fail;
-	}
+	if (!p_mngr->ilt_shadow)
+		return -ENOMEM;
 
 	DP_VERBOSE(p_hwfn, QED_MSG_ILT,
 		   "Allocated 0x%x bytes for ilt shadow\n",
-- 
2.17.1