generic_permission: MAY_OPEN is not write access
authorSerge E. Hallyn <serue@us.ibm.com>
Tue, 29 Dec 2009 20:50:19 +0000 (14:50 -0600)
committerLinus Torvalds <torvalds@linux-foundation.org>
Wed, 30 Dec 2009 20:35:44 +0000 (12:35 -0800)
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>
fs/namei.c

index 68921d9b53020d16e12021ede6188e5e642830a7..b55440baf7ab832e9d05ae8fdddc2337da57b5ed 100644 (file)
@@ -232,6 +232,7 @@ 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;