[PATCH 100/101] generic_permission: MAY_OPEN is not write access

[Greg Kroah-Hartman]

From: Serge E. Hallyn <serue@xxxxxxxxxx>

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@xxxxxxxxx>
Signed-off-by: Serge E. Hallyn <serue@xxxxxxxxxx>
Tested-by: Mike Kazantsev <mk.fraggod@xxxxxxxxx>
Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxx>
---
 fs/namei.c |    1 +
 1 files changed, 1 insertions(+), 0 deletions(-)

diff --git a/fs/namei.c b/fs/namei.c
index d11f404..a2b3c28 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -234,6 +234,7 @@ 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;
-- 
1.6.6

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