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SubjectRe: [PATCH 2/2] fix sys_unshare()+SEM_UNDO: perform an implicit CLONE_SYSVSEM in CLONE_NEWIPC
Quoting Manfred Spraul (manfred@colorfullife.com):
> 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.

So this was never an issue with clone(CLONE_NEWIPC|CLONE_SYSVSEM), which
should have had the same result as unshare(CLONE_NEWIPC&~CLONE_SYSVSEM)?

> I'm not sure who's the right maintainer, Andrew, could you merge it?
>
> Signed-off-by: Manfred Spraul <manfred@colorfullife.com>
> ---
> kernel/fork.c | 6 +++++-
> 1 files changed, 5 insertions(+), 1 deletions(-)
>
> diff --git a/kernel/fork.c b/kernel/fork.c
> index 7f242b0..6f956a7 100644
> --- a/kernel/fork.c
> +++ b/kernel/fork.c
> @@ -1735,9 +1735,13 @@ asmlinkage long sys_unshare(unsigned long unshare_flags)
> goto bad_unshare_cleanup_semundo;
>
> if (new_fs || new_mm || new_fd || new_ulist || new_nsproxy) {
> - if (unshare_flags & CLONE_SYSVSEM) {
> + if (unshare_flags & (CLONE_NEWIPC|CLONE_SYSVSEM)) {
> /*
> * CLONE_SYSVSEM is equivalent to sys_exit().
> + *
> + * CLONE_NEWIPC must also detach from the undolist: after switching
> + * to a new ipc namespace, the semaphore arrays from the old
> + * namespace are unreachable.
> */
> exit_sem(current);
> }
> --
> 1.5.4.1


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