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From:   Jing Xiangfeng <jingxiangfeng@huawei.com>
To:     <gregkh@linuxfoundation.org>, <christian.gromm@microchip.com>,
        <masahiroy@kernel.org>, <tglx@linutronix.de>,
        <keescook@chromium.org>
CC:     <devel@driverdev.osuosl.org>, <linux-kernel@vger.kernel.org>,
        <jingxiangfeng@huawei.com>
Subject: [PATCH] staging: most: don't access hdm_ch before checking it valid
Date:   Mon, 28 Sep 2020 18:48:38 +0800
Message-ID: <20200928104838.189639-1-jingxiangfeng@huawei.com>
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In try_start_dim_transfer(), pointer hdm_ch is accessed before checking.
This may lead to a potential null pointer dereference. Fix this by
dereferencing hdm_ch after calling BUG_ON().

Signed-off-by: Jing Xiangfeng <jingxiangfeng@huawei.com>
---
 drivers/staging/most/dim2/dim2.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/staging/most/dim2/dim2.c b/drivers/staging/most/dim2/dim2.c
index 509c8012d20b..ccd7cc7545e4 100644
--- a/drivers/staging/most/dim2/dim2.c
+++ b/drivers/staging/most/dim2/dim2.c
@@ -148,7 +148,7 @@ void dimcb_on_error(u8 error_id, const char *error_message)
 static int try_start_dim_transfer(struct hdm_channel *hdm_ch)
 {
 	u16 buf_size;
-	struct list_head *head = &hdm_ch->pending_list;
+	struct list_head *head;
 	struct mbo *mbo;
 	unsigned long flags;
 	struct dim_ch_state_t st;
@@ -156,6 +156,7 @@ static int try_start_dim_transfer(struct hdm_channel *hdm_ch)
 	BUG_ON(!hdm_ch);
 	BUG_ON(!hdm_ch->is_initialized);
 
+	head = &hdm_ch->pending_list;
 	spin_lock_irqsave(&dim_lock, flags);
 	if (list_empty(head)) {
 		spin_unlock_irqrestore(&dim_lock, flags);
-- 
2.17.1