linux-kernel - [PATCH 05/14] fs: check FMODE_WRITE in __kernel

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Message-Id: <20200528054043.621510-6-hch@lst.de>
Date:   Thu, 28 May 2020 07:40:34 +0200
From:   Christoph Hellwig <hch@....de>
To:     Al Viro <viro@...iv.linux.org.uk>
Cc:     Linus Torvalds <torvalds@...ux-foundation.org>,
        Ian Kent <raven@...maw.net>,
        David Howells <dhowells@...hat.com>,
        linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org,
        linux-security-module@...r.kernel.org,
        netfilter-devel@...r.kernel.org
Subject: [PATCH 05/14] fs: check FMODE_WRITE in __kernel_write

We still need to check if the fѕ is open write, even for the low-level
helper.

Signed-off-by: Christoph Hellwig <hch@....de>
---
 fs/read_write.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/fs/read_write.c b/fs/read_write.c
index 2c601d853ff3d..76be155ad9824 100644
--- a/fs/read_write.c
+++ b/fs/read_write.c
@@ -505,6 +505,8 @@ ssize_t __kernel_write(struct file *file, const void *buf, size_t count, loff_t
 	const char __user *p;
 	ssize_t ret;
 
+	if (!(file->f_mode & FMODE_WRITE))
+		return -EBADF;
 	if (!(file->f_mode & FMODE_CAN_WRITE))
 		return -EINVAL;
 
-- 
2.26.2