From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932732AbcASJOo (ORCPT ); Tue, 19 Jan 2016 04:14:44 -0500 Received: from mail-io0-f196.google.com ([209.85.223.196]:36740 "EHLO mail-io0-f196.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932515AbcASJOm (ORCPT ); Tue, 19 Jan 2016 04:14:42 -0500 From: Fredrik Markstrom To: Ingo Molnar , Peter Zijlstra Cc: Manfred Spraul , Davidlohr Bueso , David Howells , Al Viro , George Spelvin , Marcus Gelderie , linux-kernel@vger.kernel.org Subject: [PATCH 1/1] ipc/mqueue: Obey RLIM_INFINITY for message queues. Date: Tue, 19 Jan 2016 10:10:37 +0100 Message-Id: <1453194637-13996-1-git-send-email-fredrik.markstrom@gmail.com> X-Mailer: git-send-email 2.7.0 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Even if we set the "POSIX message queues" rlimit to unlimited we might fail with EMFILE. That happens when the max usage of a user wraps around on 32 bits. We fix this by: - Skipping the test in the case of RLIM_INFINITY - Changing user->mq_bytes from long to long long The accounting can't be skipped entierly for this case since rlimit can be changed from unlimited to something smaller while a message queue is open. Signed-off-by: Fredrik Markstrom --- /* Compile with: gcc -o mqt mqt.c */ #include #include #include #include int main(void) { int i; mqd_t mqs[1000]; struct mq_attr attr; attr.mq_msgsize = 70000; attr.mq_maxmsg = 10000; attr.mq_flags = 0; attr.mq_curmsgs = 0; for(i = 0; i < 1000; i++) { char name[32]; sprintf(name, "/tmq%d", i); mqs[i] = mq_open(name, O_RDWR|O_CREAT, 0644, &attr); if(mqs[i] < 0) { printf("Failed after %d mq_open\n", i); perror("mq_open"); return -1; } } printf("Success (i=%d)\n", i); return 0; } Before patch: % ulimit -c unlimited % ./mqt Failed after 6 mq_open mq_open: Too many open files After patch: % ulimit -c unlimited % ./mqt .... Success (i=1000) include/linux/sched.h | 2 +- ipc/mqueue.c | 5 +++-- 2 files changed, 4 insertions(+), 3 deletions(-) diff --git a/include/linux/sched.h b/include/linux/sched.h index edad7a4..745b7f5 100644 --- a/include/linux/sched.h +++ b/include/linux/sched.h @@ -827,7 +827,7 @@ struct user_struct { #endif #ifdef CONFIG_POSIX_MQUEUE /* protected by mq_lock */ - unsigned long mq_bytes; /* How many bytes can be allocated to mqueue? */ + unsigned long long mq_bytes; /* How many bytes can be allocated to mqueue? */ #endif unsigned long locked_shm; /* How many pages of mlocked shm ? */ diff --git a/ipc/mqueue.c b/ipc/mqueue.c index 161a180..40db042 100644 --- a/ipc/mqueue.c +++ b/ipc/mqueue.c @@ -275,8 +275,9 @@ static struct inode *mqueue_get_inode(struct super_block *sb, info->attr.mq_msgsize); spin_lock(&mq_lock); - if (u->mq_bytes + mq_bytes < u->mq_bytes || - u->mq_bytes + mq_bytes > rlimit(RLIMIT_MSGQUEUE)) { + if (rlimit(RLIMIT_MSGQUEUE) != RLIM_INFINITY && ( + u->mq_bytes + mq_bytes < u->mq_bytes || + u->mq_bytes + mq_bytes > rlimit(RLIMIT_MSGQUEUE))) { spin_unlock(&mq_lock); /* mqueue_evict_inode() releases info->messages */ ret = -EMFILE; -- 2.1.4