Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753432AbaJFSd6 (ORCPT ); Mon, 6 Oct 2014 14:33:58 -0400 Received: from mail-wg0-f41.google.com ([74.125.82.41]:51342 "EHLO mail-wg0-f41.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753345AbaJFSda (ORCPT ); Mon, 6 Oct 2014 14:33:30 -0400 From: Manfred Spraul To: Andrew Morton Cc: LKML , Davidlohr Bueso , Michael Kerrisk , Rafael Aquini , Rik van Riel , 1vier1@web.de, Manfred Spraul Subject: [PATCH 2/3] ipc/sem.c: increase SEMMSL, SEMMNI, SEMOPM Date: Mon, 6 Oct 2014 20:32:42 +0200 Message-Id: <1412620363-2759-3-git-send-email-manfred@colorfullife.com> X-Mailer: git-send-email 1.9.3 In-Reply-To: <1412620363-2759-2-git-send-email-manfred@colorfullife.com> References: <1412620363-2759-1-git-send-email-manfred@colorfullife.com> <1412620363-2759-2-git-send-email-manfred@colorfullife.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org a) SysV can be abused to allocate locked kernel memory. For most systems, a small limit doesn't make sense, see the discussion with regards to SHMMAX. Therefore: Increase the sysv sem limits so that all known applications will work with these defaults. b) With regards to the maximum supported: Some of the specified hard limits are not correct anymore, therefore the patch updates the documentation. - SEMMNI must stay below IPCMNI, which is 32768. As for SHMMAX: Stay a bit below this limit. - SEMMSL was limited to 8k, to ensure that the kmalloc for the kernel array was limited to 16 kB (order=2) This doesn't apply anymore: - the allocation size isn't sizeof(short)*nsems anymore. - ipc_alloc falls back to vmalloc - SEMOPM should stay below 1000, to limit the kmalloc in semtimedop() to an order=1 allocation. Therefore: Leave it at 500 (order=0 allocation). Note: If an administrator must limit the memory allocations, then he can set the values as necessary. Or he can disable sysv entirely (as e.g. done by Android). Signed-off-by: Manfred Spraul --- include/uapi/linux/sem.h | 18 +++++++++++++++--- 1 file changed, 15 insertions(+), 3 deletions(-) diff --git a/include/uapi/linux/sem.h b/include/uapi/linux/sem.h index 541fce0..dd73b90 100644 --- a/include/uapi/linux/sem.h +++ b/include/uapi/linux/sem.h @@ -63,10 +63,22 @@ struct seminfo { int semaem; }; -#define SEMMNI 128 /* <= IPCMNI max # of semaphore identifiers */ -#define SEMMSL 250 /* <= 8 000 max num of semaphores per id */ +/* + * SEMMNI, SEMMSL and SEMMNS are default values which can be + * modified by sysctl. + * The values has been chosen to be larger than necessary for any + * known configuration. + * + * SEMOPM should not be increased beyond 1000, otherwise there is the + * risk that semop()/semtimedop() fails due to kernel memory fragmentation when + * allocating the sop array. + */ + + +#define SEMMNI 32000 /* <= IPCMNI max # of semaphore identifiers */ +#define SEMMSL 32000 /* <= INT_MAX max num of semaphores per id */ #define SEMMNS (SEMMNI*SEMMSL) /* <= INT_MAX max # of semaphores in system */ -#define SEMOPM 32 /* <= 1 000 max num of ops per semop call */ +#define SEMOPM 500 /* <= 1 000 max num of ops per semop call */ #define SEMVMX 32767 /* <= 32767 semaphore maximum value */ #define SEMAEM SEMVMX /* adjust on exit max value */ -- 1.9.3 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/