linux-kernel - [070/118] ipc: sysv shared memory limited to 8TiB

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Message-ID: <lsq.1368193181.240724534@decadent.org.uk>
Date:	Fri, 10 May 2013 14:39:41 +0100
From:	Ben Hutchings <ben@...adent.org.uk>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:	akpm@...ux-foundation.org,
	"Linus Torvalds" <torvalds@...ux-foundation.org>,
	"Robin Holt" <holt@....com>, "Alex Thorlton" <athorlton@....com>
Subject: [070/118] ipc: sysv shared memory limited to 8TiB

3.2.45-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Robin Holt <holt@....com>

commit d69f3bad4675ac519d41ca2b11e1c00ca115cecd upstream.

Trying to run an application which was trying to put data into half of
memory using shmget(), we found that having a shmall value below 8EiB-8TiB
would prevent us from using anything more than 8TiB.  By setting
kernel.shmall greater than 8EiB-8TiB would make the job work.

In the newseg() function, ns->shm_tot which, at 8TiB is INT_MAX.

ipc/shm.c:
 458 static int newseg(struct ipc_namespace *ns, struct ipc_params *params)
 459 {
...
 465         int numpages = (size + PAGE_SIZE -1) >> PAGE_SHIFT;
...
 474         if (ns->shm_tot + numpages > ns->shm_ctlall)
 475                 return -ENOSPC;

[akpm@...ux-foundation.org: make ipc/shm.c:newseg()'s numpages size_t, not int]
Signed-off-by: Robin Holt <holt@....com>
Reported-by: Alex Thorlton <athorlton@....com>
Signed-off-by: Andrew Morton <akpm@...ux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@...ux-foundation.org>
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 include/linux/ipc_namespace.h |    2 +-
 ipc/shm.c                     |    2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

--- a/include/linux/ipc_namespace.h
+++ b/include/linux/ipc_namespace.h
@@ -42,8 +42,8 @@ struct ipc_namespace {
 
 	size_t		shm_ctlmax;
 	size_t		shm_ctlall;
+	unsigned long	shm_tot;
 	int		shm_ctlmni;
-	int		shm_tot;
 	/*
 	 * Defines whether IPC_RMID is forced for _all_ shm segments regardless
 	 * of shmctl()
--- a/ipc/shm.c
+++ b/ipc/shm.c
@@ -450,7 +450,7 @@ static int newseg(struct ipc_namespace *
 	size_t size = params->u.size;
 	int error;
 	struct shmid_kernel *shp;
-	int numpages = (size + PAGE_SIZE -1) >> PAGE_SHIFT;
+	size_t numpages = (size + PAGE_SIZE - 1) >> PAGE_SHIFT;
 	struct file * file;
 	char name[13];
 	int id;

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