From 6013f67fc1a4c7fa5bcab2d39c1eaa3e260c7ac1 Mon Sep 17 00:00:00 2001 From: Manfred Spraul <manfred@colorfullife.com> Date: Tue, 29 Apr 2008 01:00:59 -0700 Subject: [PATCH] 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> --- kernel/fork.c | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-) diff --git a/kernel/fork.c b/kernel/fork.c index 01666979beac..de5c16c6b6ec 100644 --- a/kernel/fork.c +++ b/kernel/fork.c @@ -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; -- 2.20.1