Commit 8e36709d authored by KAMEZAWA Hiroyuki's avatar KAMEZAWA Hiroyuki Committed by Linus Torvalds
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[PATCH] shmdt cannot detach not-alined shm segment cleanly.

sys_shmdt() can manage shm segments which are 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: default avatarKAMEZAWA Hiroyuki <>
Cc: Manfred Spraul <>
Acked-by: default avatarHugh Dickins <>
Cc: <>
Signed-off-by: default avatarAndrew Morton <>
Signed-off-by: default avatarLinus Torvalds <>
parent c22db941
......@@ -870,6 +870,7 @@ asmlinkage long sys_shmdt(char __user *shmaddr)
* 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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