Messages in this thread Patch in this message | | | Date | Wed, 15 Oct 2008 11:27:36 +0200 | From | Kurt Garloff <> | Subject | [PATCH 1/1] default mlock limit 32k->64k |
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Hi,
normal users can mlock memory up to the value defined in RLIMIT_MLOCK. The number used to 0 for a long time and has been changed to 8 pages (32k on 4k page systems) a number of years ago to accommodate the needs of gpg, which is one of the few programs that a normal user runs and which needs mlock (to prevent passphrase and key from leaking into swap).
Nowadays, we have gpg2, and the need has increased to 64k. Attached patch does change the default to 64k, independent of the PAGE_SIZE. (Unless PAGE_SIZE is larger than 64k, then we allow one page.)
Please apply. -- Kurt Garloff, VP Business Development -- OPS, Novell Inc. From: Kurt Garloff <garloff@suse.de> Subject: Increase default RLIMIT_MEMLOCK to 64k References: bnc#329675 Patch-Mainline: no (should be submitted)
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> --- Index: linux-2.6.27/include/linux/resource.h =================================================================== --- linux-2.6.27.orig/include/linux/resource.h +++ linux-2.6.27/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[unhandled content-type:application/pgp-signature] | |