From: Serge E. Hallyn <serue@us.ibm.com>
Date: Tue, 29 Dec 2009 20:50:19 +0000 (-0600)
Subject: generic_permission: MAY_OPEN is not write access
X-Git-Tag: v2.6.31.10~8
X-Git-Url: https://git.karo-electronics.de/?a=commitdiff_plain;h=92a5184168d552fd3e8f43d05ac04924d6aaa43b;p=karo-tx-linux.git

generic_permission: MAY_OPEN is not write access

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@gmail.com>
Signed-off-by: Serge E. Hallyn <serue@us.ibm.com>
Tested-by: Mike Kazantsev <mk.fraggod@gmail.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
---

diff --git a/fs/namei.c b/fs/namei.c
index fcfc5539252c..b224905ff98e 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -221,6 +221,7 @@ int generic_permission(struct inode *inode, int mask,
 	/*
 	 * 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;