mm: increase the default mlock limit from 32k to 64k

By default, non-privileged tasks can only mlock() a small amount of
memory to avoid a DoS attack by ordinary users.  The Linux kernel
defaulted to 32k (on a 4k page size system) to accommodate the needs of
gpg.

However, newer gpg2 needs 64k in various circumstances and otherwise
fails miserably, see bnc#329675.

Change the default to 64k, and make it more agnostic to PAGE_SIZE.

Signed-off-by: Kurt Garloff <garloff@suse.de>
Signed-off-by: Nick Piggin <npiggin@suse.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/include/linux/resource.h b/include/linux/resource.h
index aaa423a6f3d9167ed4cd77c23053b271d1874631..40fc7e62608220e9a64dd70493c3b091fa49a0b7 100644 (file)
--- a/include/linux/resource.h
+++ b/include/linux/resource.h
@@ -59,10 +59,10 @@ struct rlimit {
 #define _STK_LIM       (8*1024*1024)
 
 /*
- * GPG wants 32kB of mlocked memory, to make sure pass phrases
+ * GPG2 wants 64kB of mlocked memory, to make sure pass phrases
  * and other sensitive information are never written to disk.
  */
-#define MLOCK_LIMIT    (8 * PAGE_SIZE)
+#define MLOCK_LIMIT    ((PAGE_SIZE > 64*1024) ? PAGE_SIZE : 64*1024)
 
 /*
  * Due to binary compatibility, the actual resource numbers