linux-kernel - [ 20/49] NFSv4: dont check MAY

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Date:	Sun, 13 Jan 2013 17:43:15 +0000
From:	Ben Hutchings <ben@...adent.org.uk>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:	akpm@...ux-foundation.org, alan@...rguk.ukuu.org.uk,
	Weston Andros Adamson <dros@...app.com>,
	Trond Myklebust <Trond.Myklebust@...app.com>
Subject: [ 20/49] NFSv4: dont check MAY_WRITE access bit in OPEN

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

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

From: Weston Andros Adamson <dros@...app.com>

commit bbd3a8eee82a2a6f4aa1cce60ccb014f25e5c560 upstream.

Don't check MAY_WRITE as a newly created file may not have write mode bits,
but POSIX allows the creating process to write regardless.
This is ok because NFSv4 OPEN ops handle write permissions correctly -
the ACCESS in the OPEN compound is to differentiate READ v EXEC permissions.

Fixes a regression due to commit 6168f62c (NFSv4: Add ACCESS operation to
OPEN compound)

Signed-off-by: Weston Andros Adamson <dros@...app.com>
Signed-off-by: Trond Myklebust <Trond.Myklebust@...app.com>
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 fs/nfs/nfs4proc.c |    6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/fs/nfs/nfs4proc.c b/fs/nfs/nfs4proc.c
index 1e0faf9..ccada68 100644
--- a/fs/nfs/nfs4proc.c
+++ b/fs/nfs/nfs4proc.c
@@ -1661,10 +1661,10 @@ static int nfs4_opendata_access(struct rpc_cred *cred,
 		return 0;
 
 	mask = 0;
+	/* don't check MAY_WRITE - a newly created file may not have
+	 * write mode bits, but POSIX allows the creating process to write */
 	if (fmode & FMODE_READ)
 		mask |= MAY_READ;
-	if (fmode & FMODE_WRITE)
-		mask |= MAY_WRITE;
 	if (fmode & FMODE_EXEC)
 		mask |= MAY_EXEC;
 
@@ -1673,7 +1673,7 @@ static int nfs4_opendata_access(struct rpc_cred *cred,
 	nfs_access_set_mask(&cache, opendata->o_res.access_result);
 	nfs_access_add_cache(state->inode, &cache);
 
-	if ((mask & ~cache.mask & (MAY_READ | MAY_WRITE | MAY_EXEC)) == 0)
+	if ((mask & ~cache.mask & (MAY_READ | MAY_EXEC)) == 0)
 		return 0;
 
 	/* even though OPEN succeeded, access is denied. Close the file */


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