Subject: + ipcshm-document-new-limits-in-the-uapi-header.patch added to -mm tree
To: davidlohr@xxxxxx,manfred@xxxxxxxxxxxxxxxx,mtk.manpages@xxxxxxxxx
From: akpm@xxxxxxxxxxxxxxxxxxxx
Date: Tue, 06 May 2014 13:09:44 -0700
The patch titled
Subject: ipc,shm: document new limits in the uapi header
has been added to the -mm tree. Its filename is
ipcshm-document-new-limits-in-the-uapi-header.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/ipcshm-document-new-limits-in-the-uapi-header.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/ipcshm-document-new-limits-in-the-uapi-header.patch
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From: Davidlohr Bueso <davidlohr@xxxxxx>
Subject: ipc,shm: document new limits in the uapi header
This is useful in the future and allows users to better understand the
reasoning behind the changes.
Also use UL as we're dealing with it anyways.
Signed-off-by: Davidlohr Bueso <davidlohr@xxxxxx>
Cc: Michael Kerrisk <mtk.manpages@xxxxxxxxx>
Cc: Manfred Spraul <manfred@xxxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
include/uapi/linux/shm.h | 14 ++++++++------
1 file changed, 8 insertions(+), 6 deletions(-)
diff -puN include/uapi/linux/shm.h~ipcshm-document-new-limits-in-the-uapi-header include/uapi/linux/shm.h
--- a/include/uapi/linux/shm.h~ipcshm-document-new-limits-in-the-uapi-header
+++ a/include/uapi/linux/shm.h
@@ -8,17 +8,19 @@
#endif
/*
- * SHMMAX, SHMMNI and SHMALL are upper limits are defaults which can
- * be modified by sysctl.
+ * SHMMNI, SHMMAX and SHMALL are the default upper limits which can be
+ * modified by sysctl. Both SHMMAX and SHMALL have their default values
+ * to the maximum limit which is as large as it can be without helping
+ * userspace overflow the values. There is really nothing the kernel
+ * can do to avoid this any variables. It is therefore not advised to
+ * make them any larger. This is suitable for both 32 and 64-bit systems.
*/
-
#define SHMMIN 1 /* min shared seg size (bytes) */
#define SHMMNI 4096 /* max num of segs system wide */
-#define SHMMAX (ULONG_MAX - (1L<<24)) /* max shared seg size (bytes) */
-#define SHMALL (ULONG_MAX - (1L<<24)) /* max shm system wide (pages) */
+#define SHMMAX (ULONG_MAX - (1UL << 24)) /* max shared seg size (bytes) */
+#define SHMALL (ULONG_MAX - (1UL << 24)) /* max shm system wide (pages) */
#define SHMSEG SHMMNI /* max shared segs per process */
-
/* Obsolete, used only for backwards compatibility and libc5 compiles */
struct shmid_ds {
struct ipc_perm shm_perm; /* operation perms */
_
Patches currently in -mm which might be from davidlohr@xxxxxx are
mmvmacache-add-debug-data.patch
mmvmacache-optimize-overflow-system-wide-flushing.patch
mm-pass-vm_bug_on-reason-to-dump_page.patch
mm-pass-vm_bug_on-reason-to-dump_page-fix.patch
hugetlb-prep_compound_gigantic_page-drop-__init-marker.patch
hugetlb-add-hstate_is_gigantic.patch
hugetlb-update_and_free_page-dont-clear-pg_reserved-bit.patch
hugetlb-move-helpers-up-in-the-file.patch
hugetlb-add-support-for-gigantic-page-allocation-at-runtime.patch
m68k-call-find_vma-with-the-mmap_sem-held-in-sys_cacheflush.patch
mips-call-find_vma-with-the-mmap_sem-held.patch
arc-call-find_vma-with-the-mmap_sem-held.patch
arc-call-find_vma-with-the-mmap_sem-held-fix.patch
drm-exynos-call-find_vma-with-the-mmap_sem-held.patch
ipc-constify-ipc_ops.patch
ipc-shmc-check-for-ulong-overflows-in-shmat.patch
ipc-shmc-check-for-overflows-of-shm_tot.patch
ipc-shmc-check-for-integer-overflow-during-shmget.patch
ipc-shmc-increase-the-defaults-for-shmall-shmmax.patch
ipcshm-document-new-limits-in-the-uapi-header.patch
linux-next.patch
blackfin-ptrace-call-find_vma-with-the-mmap_sem-held.patch
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