[PATCH 5.4 303/434] qtnfmac: fix using skb after free

Greg Kroah-Hartman
2019-12-29T18:03:30Z

From: Sergey Matyukevich <sergey.matyukevich.os@quantenna.com>

[ Upstream commit 4a33f21cef84b1b933958c99ed5dac1726214b35 ]

KASAN reported use-after-free error:

[ 995.220767] BUG: KASAN: use-after-free in qtnf_cmd_send_with_reply+0x169/0x3e0 [qtnfmac]
[ 995.221098] Read of size 2 at addr ffff888213d1ded0 by task kworker/1:1/71

The issue in qtnf_cmd_send_with_reply impacts all the commands that do
not need response other then return code. For such commands, consume_skb
is used for response skb and right after that return code in response
skb is accessed.

Signed-off-by: Sergey Matyukevich <sergey.matyukevich.os@quantenna.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
drivers/net/wireless/quantenna/qtnfmac/commands.c | 6 ++++--
1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/drivers/net/wireless/quantenna/qtnfmac/commands.c b/drivers/net/wireless/quantenna/qtnfmac/commands.c
index dc0c7244b60e..c0c32805fb8d 100644
--- a/drivers/net/wireless/quantenna/qtnfmac/commands.c
+++ b/drivers/net/wireless/quantenna/qtnfmac/commands.c
@@ -83,6 +83,7 @@ static int qtnf_cmd_send_with_reply(struct qtnf_bus *bus,
struct qlink_cmd *cmd;
struct qlink_resp *resp = NULL;
struct sk_buff *resp_skb = NULL;
+ int resp_res = 0;
u16 cmd_id;
u8 mac_id;
u8 vif_id;
@@ -113,6 +114,7 @@ static int qtnf_cmd_send_with_reply(struct qtnf_bus *bus,
}

resp = (struct qlink_resp *)resp_skb->data;
+ resp_res = le16_to_cpu(resp->result);
ret = qtnf_cmd_check_reply_header(resp, cmd_id, mac_id, vif_id,
const_resp_size);
if (ret)
@@ -128,8 +130,8 @@ out:
else
consume_skb(resp_skb);

- if (!ret && resp)
- return qtnf_cmd_resp_result_decode(le16_to_cpu(resp->result));
+ if (!ret)
+ return qtnf_cmd_resp_result_decode(resp_res);

pr_warn("VIF%u.%u: cmd 0x%.4X failed: %d\n",
mac_id, vif_id, cmd_id, ret);
--
2.20.1