linux-kernel - [ 090/167] [PATCH] NFSv4: Ensure that we check lock exclusive/shared type against open modes

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Message-Id: <20120509055042.231589453@decadent.org.uk>
Date:	Wed, 09 May 2012 06:51:59 +0100
From:	Ben Hutchings <ben@...adent.org.uk>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:	torvalds@...ux-foundation.org, akpm@...ux-foundation.org,
	alan@...rguk.ukuu.org.uk,
	Trond Myklebust <Trond.Myklebust@...app.com>
Subject: [ 090/167] [PATCH] NFSv4: Ensure that we check lock exclusive/shared type
 against open modes

3.2-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Trond Myklebust <Trond.Myklebust@...app.com>

commit 55725513b5ef9d462aa3e18527658a0362aaae83 upstream.

Since we may be simulating flock() locks using NFS byte range locks,
we can't rely on the VFS having checked the file open mode for us.

Signed-off-by: Trond Myklebust <Trond.Myklebust@...app.com>
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 fs/nfs/nfs4proc.c |   14 ++++++++++++++
 1 file changed, 14 insertions(+)

diff --git a/fs/nfs/nfs4proc.c b/fs/nfs/nfs4proc.c
index 3c787d0..ba837d9 100644
--- a/fs/nfs/nfs4proc.c
+++ b/fs/nfs/nfs4proc.c
@@ -4726,6 +4726,20 @@ nfs4_proc_lock(struct file *filp, int cmd, struct file_lock *request)
 
 	if (state == NULL)
 		return -ENOLCK;
+	/*
+	 * Don't rely on the VFS having checked the file open mode,
+	 * since it won't do this for flock() locks.
+	 */
+	switch (request->fl_type & (F_RDLCK|F_WRLCK|F_UNLCK)) {
+	case F_RDLCK:
+		if (!(filp->f_mode & FMODE_READ))
+			return -EBADF;
+		break;
+	case F_WRLCK:
+		if (!(filp->f_mode & FMODE_WRITE))
+			return -EBADF;
+	}
+
 	do {
 		status = nfs4_proc_setlk(state, cmd, request);
 		if ((status != -EAGAIN) || IS_SETLK(cmd))
-- 
1.7.10



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