netdev - [PATCH net] NFC: netlink: fix sleep in atomic bug when firmware download timeout

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Message-Id: <20220504055847.38026-1-duoming@zju.edu.cn>
Date:   Wed,  4 May 2022 13:58:47 +0800
From:   Duoming Zhou <duoming@....edu.cn>
To:     krzysztof.kozlowski@...aro.org, linux-kernel@...r.kernel.org
Cc:     davem@...emloft.net, edumazet@...gle.com, kuba@...nel.org,
        pabeni@...hat.com, netdev@...r.kernel.org,
        Duoming Zhou <duoming@....edu.cn>
Subject: [PATCH net] NFC: netlink: fix sleep in atomic bug when firmware download timeout

There are sleep in atomic bug that could cause kernel panic during
firmware download process. The root cause is that nlmsg_new with
GFP_KERNEL parameter is called in fw_dnld_timeout which is a timer
handler. The call trace is shown below:

BUG: sleeping function called from invalid context at include/linux/sched/mm.h:265
Call Trace:
kmem_cache_alloc_node
__alloc_skb
nfc_genl_fw_download_done
call_timer_fn
__run_timers.part.0
run_timer_softirq
__do_softirq
...

The nlmsg_new with GFP_KERNEL parameter may sleep during memory
allocation process, and the timer handler is run as the result of
a "software interrupt" that should not call any other function
that could sleep.

This patch changes allocation mode of netlink message from GFP_KERNEL
to GFP_ATOMIC in order to prevent sleep in atomic bug. The GFP_ATOMIC
flag makes memory allocation operation could be used in atomic context.

Fixes: 9674da8759df ("NFC: Add firmware upload netlink command")
Fixes: 9ea7187c53f6 ("NFC: netlink: Rename CMD_FW_UPLOAD to CMD_FW_DOWNLOAD")
Signed-off-by: Duoming Zhou <duoming@....edu.cn>
---
 net/nfc/netlink.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/net/nfc/netlink.c b/net/nfc/netlink.c
index f184b0db79d..7c62417ccfd 100644
--- a/net/nfc/netlink.c
+++ b/net/nfc/netlink.c
@@ -1244,7 +1244,7 @@ int nfc_genl_fw_download_done(struct nfc_dev *dev, const char *firmware_name,
 	struct sk_buff *msg;
 	void *hdr;

-	msg = nlmsg_new(NLMSG_DEFAULT_SIZE, GFP_KERNEL);
+	msg = nlmsg_new(NLMSG_DEFAULT_SIZE, GFP_ATOMIC);
 	if (!msg)
 		return -ENOMEM;

@@ -1260,7 +1260,7 @@ int nfc_genl_fw_download_done(struct nfc_dev *dev, const char *firmware_name,

 	genlmsg_end(msg, hdr);

-	genlmsg_multicast(&nfc_genl_family, msg, 0, 0, GFP_KERNEL);
+	genlmsg_multicast(&nfc_genl_family, msg, 0, 0, GFP_ATOMIC);

 	return 0;

-- 
2.17.1