[31/39] generic_permission: MAY_OPEN is not write access

From: Greg KH
Date: Tue Jan 05 2010 - 15:08:55 EST


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

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

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 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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