linux-kernel - [PATCH] staging: rtlwifi: Fix a possible sleep-in-atomic-context bug in _is_fw_read_cmd

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Date:   Wed, 20 Jun 2018 10:58:01 +0800
From:   Jia-Ju Bai <baijiaju1990@...il.com>
To:     gregkh@...uxfoundation.org, Larry.Finger@...inger.net,
        garsilva@...eddedor.com, pkshih@...ltek.com
Cc:     devel@...verdev.osuosl.org, linux-kernel@...r.kernel.org,
        Jia-Ju Bai <baijiaju1990@...il.com>
Subject: [PATCH] staging: rtlwifi: Fix a possible sleep-in-atomic-context bug in _is_fw_read_cmd_down()

The driver may sleep with holding a spinlock.
The function call path (from bottom to top) in Linux-4.16.7 is:

[FUNC] schedule
drivers/staging/rtlwifi/halmac/rtl_halmac.c, 884: 
		schedule in _is_fw_read_cmd_down
drivers/staging/rtlwifi/halmac/rtl_halmac.c, 912: 
		_is_fw_read_cmd_down in rtl_halmac_send_h2c
drivers/staging/rtlwifi/halmac/rtl_halmac.c, 907: 
		_raw_spin_lock_irqsave in rtl_halmac_send_h2c

To fix this bug, schedule() is replaced with mdelay(1).

This bug is found by my static analysis tool (DSAC-2) and checked by
my code review.

Signed-off-by: Jia-Ju Bai <baijiaju1990@...il.com>
---
 drivers/staging/rtlwifi/halmac/rtl_halmac.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/staging/rtlwifi/halmac/rtl_halmac.c b/drivers/staging/rtlwifi/halmac/rtl_halmac.c
index 66f0a6dfc52c..e921a62e72a3 100644
--- a/drivers/staging/rtlwifi/halmac/rtl_halmac.c
+++ b/drivers/staging/rtlwifi/halmac/rtl_halmac.c
@@ -881,7 +881,7 @@ static bool _is_fw_read_cmd_down(struct rtl_priv *rtlpriv, u8 msgbox_num)
 		if (valid == 0)
 			read_down = true;
 		else
-			schedule();
+			mdelay(1);
 	} while ((!read_down) && (retry_cnts--));
 
 	return read_down;
-- 
2.17.0