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From:   ZhaoLong Wang <wangzhaolong1@huawei.com>
To:     <miquel.raynal@bootlin.com>, <richard@nod.at>, <vigneshr@ti.com>
CC:     <linux-mtd@lists.infradead.org>, <linux-kernel@vger.kernel.org>,
        <chengzhihao1@huawei.com>, <wangzhaolong1@huawei.com>,
        <yi.zhang@huawei.com>, <yangerkun@huawei.com>
Subject: [RFC] mtd: Fix error code loss in mtdchar_read() function.
Date:   Sat, 23 Sep 2023 08:58:56 +0800
Message-ID: <20230923005856.2538223-1-wangzhaolong1@huawei.com>
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In the first while loop, if the mtd_read() function returns -EBADMSG
and 'retlen' returns 0, the loop break and the function returns value
'total_retlen' is 0, not the error code.

This problem causes the user-space program to encounter EOF when it has
not finished reading the mtd partion, and this also violates the read
system call standard in POSIX.

Link: https://bugzilla.kernel.org/show_bug.cgi?id=217939
Signed-off-by: ZhaoLong Wang <wangzhaolong1@huawei.com>
---
 drivers/mtd/mtdchar.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/mtd/mtdchar.c b/drivers/mtd/mtdchar.c
index 8dc4f5c493fc..ba60dc6bef98 100644
--- a/drivers/mtd/mtdchar.c
+++ b/drivers/mtd/mtdchar.c
@@ -211,7 +211,7 @@ static ssize_t mtdchar_read(struct file *file, char __user *buf, size_t count,
 	}
 
 	kfree(kbuf);
-	return total_retlen;
+	return total_retlen ? total_retlen : ret;
 } /* mtdchar_read */
 
 static ssize_t mtdchar_write(struct file *file, const char __user *buf, size_t count,
-- 
2.31.1