[ 089/104] ipc: sysv shared memory limited to 8TiB

Greg Kroah-Hartman
2013-05-06T23:19:56Z

From: Robin Holt <holt@sgi.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@linux-foundation.org: make ipc/shm.c:newseg()'s numpages size_t, not int]
Signed-off-by: Robin Holt <holt@sgi.com>
Reported-by: Alex Thorlton <athorlton@sgi.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
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
@@ -43,8 +43,8 @@ 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
@@ -462,7 +462,7 @@ 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;