linux-kernel - Re: [syzbot] [dri?] [media?] memory leak in get_sg

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Date: Mon,  1 Jan 2024 10:42:58 +0800
From: Edward Adam Davis <eadavis@...com>
To: syzbot+9b4adfed366b14496e7e@...kaller.appspotmail.com
Cc: linux-kernel@...r.kernel.org,
	syzkaller-bugs@...glegroups.com
Subject: Re: [syzbot] [dri?] [media?] memory leak in get_sg_table

please test memory leak in get_sg_table

#syz test https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git fbafc3e621c3

diff --git a/drivers/dma-buf/dma-buf.c b/drivers/dma-buf/dma-buf.c
index 21916bba77d5..709260211546 100644
--- a/drivers/dma-buf/dma-buf.c
+++ b/drivers/dma-buf/dma-buf.c
@@ -471,8 +471,11 @@ static long dma_buf_ioctl(struct file *file,
 
 		if (sync.flags & DMA_BUF_SYNC_END)
 			ret = dma_buf_end_cpu_access(dmabuf, direction);
-		else
+		else {
+			if (dmabuf->doing)
+				return -EBUSY;
 			ret = dma_buf_begin_cpu_access(dmabuf, direction);
+		}
 
 		return ret;
 
diff --git a/drivers/dma-buf/udmabuf.c b/drivers/dma-buf/udmabuf.c
index c40645999648..ed98c0319e03 100644
--- a/drivers/dma-buf/udmabuf.c
+++ b/drivers/dma-buf/udmabuf.c
@@ -152,6 +152,7 @@ static int begin_cpu_udmabuf(struct dma_buf *buf,
 	struct device *dev = ubuf->device->this_device;
 	int ret = 0;
 
+	buf->doing = true;
 	if (!ubuf->sg) {
 		ubuf->sg = get_sg_table(dev, buf, direction);
 		if (IS_ERR(ubuf->sg)) {
@@ -162,6 +163,7 @@ static int begin_cpu_udmabuf(struct dma_buf *buf,
 		dma_sync_sg_for_cpu(dev, ubuf->sg->sgl, ubuf->sg->nents,
 				    direction);
 	}
+	buf->doing = false;
 
 	return ret;
 }
diff --git a/include/linux/dma-buf.h b/include/linux/dma-buf.h
index 3f31baa3293f..4316ad0e6155 100644
--- a/include/linux/dma-buf.h
+++ b/include/linux/dma-buf.h
@@ -446,6 +446,7 @@ struct dma_buf {
 		struct dma_buf *dmabuf;
 	} *sysfs_entry;
 #endif
+	bool doing;
 };
 
 /**