Messages in this thread Patch in this message | | | Date | Thu, 09 Feb 2006 10:21:36 +0900 | From | KAMEZAWA Hiroyuki <> | Subject | [BUGFIX][PATCH] shmdt cannot detach not-alined shm segment cleanly. |
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This is a patch for a problem of shmdt(). It is found by a test, not a serious problem. -- Kame
sys_shmdt() can manages shm segments which is covered by multiple vmas. (This can happen when a user uses mprotect() after shmat().)
This works well if shm is aligned to PAGE_SIZE, but if not, the last segment cannot be detached. It is because a comparison in sys_shmdt()
(vma->vm_end - addr) < size addr == return address of shmat() size == shmsize, argments to shmget()
size should be aligned to PAGE_SIZE before being compared with vma->vm_end, which is aligned.
Signed-Off-By:KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Index: linux-2.6.16-rc2.org/ipc/shm.c =================================================================== --- linux-2.6.16-rc2.org.orig/ipc/shm.c +++ linux-2.6.16-rc2.org/ipc/shm.c @@ -870,6 +870,7 @@ asmlinkage long sys_shmdt(char __user *s * could possibly have landed at. Also cast things to loff_t to * prevent overflows and make comparisions vs. equal-width types. */ + size = PAGE_ALIGN(size); while (vma && (loff_t)(vma->vm_end - addr) <= size) { next = vma->vm_next;
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