linux-kernel - [PATCH] dma-buf: call dma_buf_stats_setup after dmabuf is in valid list

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Date:   Tue, 10 May 2022 01:19:57 +0530
From:   Charan Teja Kalla <quic_charante@...cinc.com>
To:     <sumit.semwal@...aro.org>, <christian.koenig@....com>,
        <hridya@...gle.com>, <daniel.vetter@...ll.ch>,
        <gregkh@...uxfoundation.org>
CC:     <linux-media@...r.kernel.org>, <dri-devel@...ts.freedesktop.org>,
        <linaro-mm-sig@...ts.linaro.org>, <linux-kernel@...r.kernel.org>,
        <tjmercier@...gle.com>,
        Charan Teja Reddy <quic_charante@...cinc.com>
Subject: [PATCH] dma-buf: call dma_buf_stats_setup after dmabuf is in valid list

From: Charan Teja Reddy <quic_charante@...cinc.com>

When dma_buf_stats_setup() fails, it closes the dmabuf file which
results into the calling of dma_buf_file_release() where it does
list_del(&dmabuf->list_node) with out first adding it to the proper
list. This is resulting into panic in the below path:
__list_del_entry_valid+0x38/0xac
dma_buf_file_release+0x74/0x158
__fput+0xf4/0x428
____fput+0x14/0x24
task_work_run+0x178/0x24c
do_notify_resume+0x194/0x264
work_pending+0xc/0x5f0

Fix it by moving the dma_buf_stats_setup() after dmabuf is added to the
list.

Fixes: bdb8d06dfefd ("dmabuf: Add the capability to expose DMA-BUF stats in sysfs")
Signed-off-by: Charan Teja Reddy <quic_charante@...cinc.com>
---
 drivers/dma-buf/dma-buf.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/drivers/dma-buf/dma-buf.c b/drivers/dma-buf/dma-buf.c
index 602b12d..a6fc96e 100644
--- a/drivers/dma-buf/dma-buf.c
+++ b/drivers/dma-buf/dma-buf.c
@@ -543,10 +543,6 @@ struct dma_buf *dma_buf_export(const struct dma_buf_export_info *exp_info)
 	file->f_mode |= FMODE_LSEEK;
 	dmabuf->file = file;
 
-	ret = dma_buf_stats_setup(dmabuf);
-	if (ret)
-		goto err_sysfs;
-
 	mutex_init(&dmabuf->lock);
 	INIT_LIST_HEAD(&dmabuf->attachments);
 
@@ -554,6 +550,10 @@ struct dma_buf *dma_buf_export(const struct dma_buf_export_info *exp_info)
 	list_add(&dmabuf->list_node, &db_list.head);
 	mutex_unlock(&db_list.lock);
 
+	ret = dma_buf_stats_setup(dmabuf);
+	if (ret)
+		goto err_sysfs;
+
 	return dmabuf;
 
 err_sysfs:
-- 
2.7.4