Commit 6013f67f authored Apr 29, 2008 by Manfred Spraul Committed by Linus Torvalds Apr 29, 2008

ipc: sysvsem: force unshare(CLONE_SYSVSEM) when CLONE_NEWIPC



sys_unshare(CLONE_NEWIPC) doesn't handle the undo lists properly, this can
cause a kernel memory corruption.  CLONE_NEWIPC must detach from the existing
undo lists.

Fix, part 2: perform an implicit CLONE_SYSVSEM in CLONE_NEWIPC.  CLONE_NEWIPC
creates a new IPC namespace, the task cannot access the existing semaphore
arrays after the unshare syscall.  Thus the task can/must detach from the
existing undo list entries, too.

This fixes the kernel corruption, because it makes it impossible that
undo records from two different namespaces are in sysvsem.undo_list.

Signed-off-by: Manfred Spraul <manfred@colorfullife.com>
Signed-off-by: Serge E. Hallyn <serue@us.ibm.com>
Acked-by: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: Pavel Emelyanov <xemul@openvz.org>
Cc: Michael Kerrisk <mtk.manpages@googlemail.com>
Cc: Pierre Peiffer <peifferp@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

parent 9edff4ab

kernel/fork.c

+6 −1

Original line number	Diff line number	Diff line
		@@ -1696,7 +1696,12 @@ asmlinkage long sys_unshare(unsigned long unshare_flags)
		CLONE_NEWNET))
		goto bad_unshare_out;

		if (unshare_flags & CLONE_SYSVSEM)
		/*
		* CLONE_NEWIPC must also detach from the undolist: after switching
		* to a new ipc namespace, the semaphore arrays from the old
		* namespace are unreachable.
		*/
		if (unshare_flags & (CLONE_NEWIPC\|CLONE_SYSVSEM))
		do_sysvsem = 1;
		if ((err = unshare_thread(unshare_flags)))
		goto bad_unshare_out;

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