[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: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> Cc: Manfred Spraul <manfred@colorfullife.com> Acked-by: Hugh Dickins <hugh@veritas.com> Cc: <stable@kernel.org> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>

[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: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> Cc: Manfred Spraul <manfred@colorfullife.com> Acked-by: Hugh Dickins <hugh@veritas.com> Cc: <stable@kernel.org> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
KAMEZAWA Hiroyuki · Linus Torvalds
1 parent c22db94127
Showing 1 changed file with 1 additions and 0 deletions Side-by-side Diff
ipc/shm.c
@@ -870,6 +870,7 @@
 	 * 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;
...	...	@@ -870,6 +870,7 @@
870	870	* could possibly have landed at. Also cast things to loff_t to
871	871	* prevent overflows and make comparisions vs. equal-width types.
872	872	*/
	873	+ size = PAGE_ALIGN(size);
873	874	while (vma && (loff_t)(vma->vm_end - addr) <= size) {
874	875	next = vma->vm_next;
875	876