linux-kernel - [PATCH AUTOSEL 4.14 1/9] media: v4l2-mem2mem: add lock to protect parameter num

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Date:   Sun, 23 Jul 2023 21:35:43 -0400
From:   Sasha Levin <sashal@...nel.org>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:     Yunfei Dong <yunfei.dong@...iatek.com>,
        Pina Chen <pina.chen@...iatek.com>,
        Hans Verkuil <hverkuil-cisco@...all.nl>,
        Sasha Levin <sashal@...nel.org>, matthias.bgg@...il.com,
        linux-media@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-mediatek@...ts.infradead.org
Subject: [PATCH AUTOSEL 4.14 1/9] media: v4l2-mem2mem: add lock to protect parameter num_rdy

From: Yunfei Dong <yunfei.dong@...iatek.com>

[ Upstream commit 56b5c3e67b0f9af3f45cf393be048ee8d8a92694 ]

Getting below error when using KCSAN to check the driver. Adding lock to
protect parameter num_rdy when getting the value with function:
v4l2_m2m_num_src_bufs_ready/v4l2_m2m_num_dst_bufs_ready.

kworker/u16:3: [name:report&]BUG: KCSAN: data-race in v4l2_m2m_buf_queue
kworker/u16:3: [name:report&]

kworker/u16:3: [name:report&]read-write to 0xffffff8105f35b94 of 1 bytes by task 20865 on cpu 7:
kworker/u16:3:  v4l2_m2m_buf_queue+0xd8/0x10c

Signed-off-by: Pina Chen <pina.chen@...iatek.com>
Signed-off-by: Yunfei Dong <yunfei.dong@...iatek.com>
Signed-off-by: Hans Verkuil <hverkuil-cisco@...all.nl>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 include/media/v4l2-mem2mem.h | 18 ++++++++++++++++--
 1 file changed, 16 insertions(+), 2 deletions(-)

diff --git a/include/media/v4l2-mem2mem.h b/include/media/v4l2-mem2mem.h
index e157d5c9b224e..239bcc4b7e95a 100644
--- a/include/media/v4l2-mem2mem.h
+++ b/include/media/v4l2-mem2mem.h
@@ -392,7 +392,14 @@ void v4l2_m2m_buf_queue(struct v4l2_m2m_ctx *m2m_ctx,
 static inline
 unsigned int v4l2_m2m_num_src_bufs_ready(struct v4l2_m2m_ctx *m2m_ctx)
 {
-	return m2m_ctx->out_q_ctx.num_rdy;
+	unsigned int num_buf_rdy;
+	unsigned long flags;
+
+	spin_lock_irqsave(&m2m_ctx->out_q_ctx.rdy_spinlock, flags);
+	num_buf_rdy = m2m_ctx->out_q_ctx.num_rdy;
+	spin_unlock_irqrestore(&m2m_ctx->out_q_ctx.rdy_spinlock, flags);
+
+	return num_buf_rdy;
 }
 
 /**
@@ -404,7 +411,14 @@ unsigned int v4l2_m2m_num_src_bufs_ready(struct v4l2_m2m_ctx *m2m_ctx)
 static inline
 unsigned int v4l2_m2m_num_dst_bufs_ready(struct v4l2_m2m_ctx *m2m_ctx)
 {
-	return m2m_ctx->cap_q_ctx.num_rdy;
+	unsigned int num_buf_rdy;
+	unsigned long flags;
+
+	spin_lock_irqsave(&m2m_ctx->cap_q_ctx.rdy_spinlock, flags);
+	num_buf_rdy = m2m_ctx->cap_q_ctx.num_rdy;
+	spin_unlock_irqrestore(&m2m_ctx->cap_q_ctx.rdy_spinlock, flags);
+
+	return num_buf_rdy;
 }
 
 /**
-- 
2.39.2