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@zju.edu.cn>
Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Link: https://lore.kernel.org/r/20220504055847.38026-1-duoming@zju.edu.cn
Signed-off-by: Paolo Abeni <pabeni@redhat.com>

diff --git a/net/nfc/netlink.c b/net/nfc/netlink.c
index f184b0d..7c62417 100644 (file)
--- 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;