linux-kernel - [31/39] generic_permission: MAY

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Date:	Tue, 05 Jan 2010 12:02:27 -0800
From:	Greg KH <gregkh@...e.de>
To:	linux-kernel@...r.kernel.org, stable@...nel.org,
	akpm@...ux-foundation.org, torvalds@...ux-foundation.org,
	stable-review@...nel.org
Cc:	"Serge E. Hallyn" <serue@...ibm.com>
Subject: [31/39] generic_permission: MAY_OPEN is not write access

2.6.31-stable review patch.  If anyone has any objections, please let us know.

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

From: Serge E. Hallyn <serue@...ibm.com>

commit 7ea6600148c265b1fd53e521022b1d7aec81d974 upstream.

generic_permission was refusing CAP_DAC_READ_SEARCH-enabled
processes from opening DAC-protected files read-only, because
do_filp_open adds MAY_OPEN to the open mask.

Ignore MAY_OPEN.  After this patch, CAP_DAC_READ_SEARCH is
again sufficient to open(fname, O_RDONLY) on a file to which
DAC otherwise refuses us read permission.

Reported-by: Mike Kazantsev <mk.fraggod@...il.com>
Signed-off-by: Serge E. Hallyn <serue@...ibm.com>
Tested-by: Mike Kazantsev <mk.fraggod@...il.com>
Signed-off-by: Linus Torvalds <torvalds@...ux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@...e.de>

---
 fs/namei.c |    1 +
 1 file changed, 1 insertion(+)

--- a/fs/namei.c
+++ b/fs/namei.c
@@ -221,6 +221,7 @@ int generic_permission(struct inode *ino
 	/*
 	 * Searching includes executable on directories, else just read.
 	 */
+	mask &= MAY_READ | MAY_WRITE | MAY_EXEC;
 	if (mask == MAY_READ || (S_ISDIR(inode->i_mode) && !(mask & MAY_WRITE)))
 		if (capable(CAP_DAC_READ_SEARCH))
 			return 0;

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